Rebuilding a Hybrid Vehicle Battery Pack


Inside this Article

2003 Honda Civic Hybrid
2003 Honda Civic Hybrid
ACCESSING THE BATTERIES - Removing the rear seat. There are three 10 mm bolts, one on either side of the seat (as shown) and one near the middle of the seat.
ACCESSING THE BATTERIES - Removing the seat reveals the main battery box cover.
LOCATING THE MAIN CIRCUIT BREAKER - Remove the main circuit breaker cover. Make sure it’s in the “off” position and remove the red plastic safety cover, breaking off the plastic pin.
LOCATING THE MAIN CIRCUIT BREAKER - Remove the main circuit breaker cover. Make sure it’s in the “off” position and remove the red plastic safety cover, breaking off the plastic pin.
GETTING TO THE BATTERIES - In the car, with the battery box cover and seats out. Note the yellow wire for the external charging port.
ACCESSING THE SENSOR WIRES - The main power connection: The three sensor connectors sit above the positive and negative wires.
FINDING THE FOURTH SENSOR - The fourth sensor connector sits below the main positive and negative wires.
THE BATTERY PACK, REMOVED - The circuit breaker fuse and the wiring side of the pack.
THE REMOVED CIRCUIT BREAKER ASSEMBLY - Take care to keep track of the twenty 10 mm bolts and temperature sensor wire routing; note the four round metal spacers—where the circuit breaker makes its electrical connections to the sticks.
REMOVING STICKS FROM THEIR HOUSING - The orange bus bar and some of the sticks are removed.
REMOVING STICKS FROM THEIR HOUSING - Each stick is fully charged before starting the discharge/charge reconditioning cycles.
CHARGING A STICK - A stick connected to the charger to be reconditioned.
FINISHED STICKS - A pile of finished sticks with final Ah ratings written on each. Note the small metal thermal sensor tabs on each stick.
2003 Honda Civic Hybrid

Reconditioning NiMh hybrid car battery packs is time-consuming—you cannot rush it! However, if you have the patience, reconditioning them yourself can save you more than 90% of the cost of having a car a dealer do the job.

Last fall, I bought my friend’s dysfunctional 2003 Civic Hybrid. It was not something I needed, but it did have only 110,000 miles on the odometer and some nice custom features—and it was cheap! Plus, it had been well-maintained: All the dealer checkups and service had been properly performed.

But besides the car’s computer spewing some error codes, it also had performance issues suggesting expensive battery problems. The car was very sluggish and its mpg had dropped off—from more than 50 mpg to 35 to 40 mpg. It stalled easily; the auto-stop function—which turns off the IC engine when the car comes to a full stop—did not work; and, of course, the “check engine” and integrated motor assist (IMA) warning lights wouldn’t shut off.

The Honda dealership wanted $3,200 to replace the battery pack with a factory-refurbished one (new cells are not available for a Civic Hybrid of that vintage). Replacement battery packs are made from dead packs dealers return to Honda, which recovers the remaining good subpacks for reuse. These refurbished packs include a one-year factory warranty. There is at least one third-party that claims to do the same thing for $1,250, but you have to sell him your old battery pack first, which he uses for salvageable parts. The few online bloggings from DIYers who tried reconditioning their own packs were not very insightful. However, by doing a lot of “reading between the lines,” I felt I learned enough to try my hand at refurbishing.

The root of the batteries’ underperformance had to do with the nickel metal hydride (NiMH) cells getting warm from discharging and charging. After thousands of cycles, the fine nickel powder inside starts to form larger nickel crystals, which eventually impede the electrons from flowing. If the crystals get big enough, they can puncture the separators between the positive and negative sides of the cell, shorting the cell. Reconditioning helps break up these crystals. Although it won’t make the cell like new, it’ll result in a better-functioning cell.

Preliminary Precautions

All you need to recondition IMA battery packs are a few basic tools: a good digital multimeter; the right charger/reconditioning machine (there are several to choose from online); a #30 Torx driver; standard hand tools; and, most importantly, the will and time to do the work right. Because this project can take several weeks of charging, you may need a second car to drive until the project is completed.

Hybrid car blogs published plenty of warnings about getting electrocuted from the batteries. Since this was new territory for me, I took this advice seriously—but there is only one place on a battery pack where any real hazard exists: from voltage across the full pack, which can be up to 180 VDC.

That single location is easily found with a multimeter, and once you turn off the IMA pack’s built-in circuit breaker and start unbolting the individual subpacks, the risk drops significantly since the sticks are only about 8 V each. Honda designed the battery pack in an almost idiot-proof way. The terminal bolts and other fasteners are arranged so that it is easy to avoid touching two ends of any higher-voltage terminals at the same time. Common sense coupled with basic mechanical skills meet most everything else you come across during this task. But working carelessly can still hurt, as well as cause you expensive additional repairs.

Dissassembling the System

Start by parking the car in a place it can stay for a month or two. Finding that you need to move the car after you’ve removed the battery pack is a real bummer, since the car will not move under its own power without a working battery pack.

Next, remove the rear seat cushions (three 10 mm bolts and some plastic clips). Then take off the small cover over the battery box’s circuit breaker (two bolts, #30 Torx), remove its red plastic safety cover and turn off the circuit breaker. The 180 VDC electrical hazard is now gone—the breaker separates about 40% of the sticks from the rest of the pack. Nonetheless, be careful as you work. To get the main cover off, you will need to break off the little black plastic safety snap/pin to the right of the circuit breaker with a large, flat screwdriver.

Remove the metal main battery box cover (six bolts, #30 Torx) and slide the entire cover up an inch or two to release the two metal fingers on the extreme right and left of the cover. You may need to have someone hold the seatbelts to one side to do this.

Once the cover is off, you will find a bewildering array of wiring and connectors. If you disconnect the 12 V battery (yes, there is a standard car battery, too) in the engine compartment, even that small hazard is eliminated. To do this, disconnect the cable at the negative battery post and insulate the end completely with electrical tape or a similar insulating material. This is safer than disconnecting the positive side and less likely to create a short to the chassis. In any case, continue to be careful not to bang up anything since replacing broken terminals or repairing cut wiring is a major and unnecessary chore.

Inside the battery box, remove the three 10 mm bolts that hold the two main IMA power wires and ground wire for the battery pack. Unplug the five sensor connectors from the pack. Then remove the four 12 mm bolts that hold the battery pack in the metal box (two on the top of the pack and two on the bottom). Gently bend any wires out of the way and lift out the battery pack. It weighs about 50 pounds and you will be stooped over in an awkward position, so protect your back and consider having a friend help with the lift.

Use the existing carry straps to lift it, being careful not to get tangled up with any wires. Take a few photos as you go along so you remember where everything goes in a month (or two) after completion.

Preparing for Reconditioning

I set up my work area in the living room, since it is climate-controlled and well-illuminated. Find an organizable work area, because there will be no less than 90 assorted bolts and screws holding the pack together. As you take apart the pack to access the subpack sticks inside, you’ll need to keep a close count of all the fasteners—use a spill-proof container! 

You cannot disassemble the sticks—they are welded together in groups of six cells and tightly wrapped in yellow plastic. These yellow sticks are what you will be “reconditioning” with your new charger/reconditioner machine. Remove each stick from the plastic holding frame to allow for easy judging of how warm each cell gets as reconditioning proceeds. Each stick has a “square” end and a “hex” end. The positive side is the square—mark it as such to avoid confusion. If you do connect the charger in the wrong polarity, it is smart enough to scream at you and display “connection reversed” before any damage can be done to the cells.

Be careful of the small sensor wires attached to three of the sticks—they pull apart easily and are a major pain to put back again. These three sticks can only be removed from the frame by firmly pushing them from right to left (looking at the pack as it would be in the car). The sensor wires are not very long, so carefully bend them so the sticks they are attached to are not pulling on them. Remember (and take photos of) how the wires are routed around the pack and where their little holders snap together. They will only fit in one way without making trouble for you when reassembly starts.

Reconditioning the Sticks

Although NiMh cells were once thought to be “memory-proof,” all nickel-based batteries develop memory problems; NiMhs are just much more resistant to the problem than NiCd cells.

Deep cycling has always been the method of minimizing, and somewhat repairing, memory issues. This is what your charger/reconditioner does, in a very sophisticated way. Its computer brain monitors the cycling cells to optimize breaking up the microscopic nickel “crystals” that form as a cell ages with use. The reconditioning is not perfect and will never make the cell factory-fresh again, but it does go far in making the cell work as well as it can.

Follow the charger manufacturer’s instructions for setting up your reconditioner for NiMh cells. Be sure you understand the instructions. I used an iMax B6 ($55) and the instructions had to have been written by someone whose English was not great—it was difficult to understand at first. 

Do not despair if the instructions are too difficult to decipher. The default settings for each type of battery (which are already programmed into the charger) seem to work well enough. But I changed the minimum cell state on mine to 0.8 V per cell, just to get a little deeper discharge and, hopefully, a more functional battery in the end. Do not discharge them too far, which can cause cell polarity reversal, which means you end up with a dead stick!

Number the sticks with a permanent black marker to avoid mixing them up. Have a pad of paper and pen handy to record the values the screen displays at the end of each programmed cycle to track how each stick performed. Believe me, after a month or more of this, it is a hopeless task remembering it all.

Fully charge each stick before starting the discharge/charge reconditioning cycles. But before the lengthy cycling process starts, set the machine for a minimum of three discharge-charge cycles. My iMax can do up to five cycles automatically, but you don’t really need to spend that much time on each stick to sort the good from the bad. With the good sticks, more than three cycles does not necessarily make the stick perform significantly better. If a stick is somewhere “between” good and bad, then the cycling process often straightens it out nicely.

With the iMax B6, each cycle takes at least 10 hours to complete. Multiply that by 20 sticks and you can quickly see that reconditioning the entire pack will take 25 days of round-the-clock reconditioning. Try to time your “starts and stops” so that the charger alarm doesn’t wake you up in the middle of the night, though the alarm can be turned off.

The iMax B6 is made for small, radio-controlled batteries, and with light loading to keep the cells from getting too hot, the IMA conditioning process is lengthy. But it does get the job done with IMA sticks too, and it is less expensive than similar devices. Other reconditioners use much higher discharge rates and cycle faster. However, the additional heat may also cause otherwise-OK sticks to be heat-damaged.

If the stick is working right, it will feel slightly warmer than room temperature and all the cells will be the same temperature during the process. It should also charge to about 6,400 mAh when full and do it in a bit more than one hour from a minimal state of charge (0.8 V per cell). If all goes well, the final numbers in the display will be about 6,400 mAh charged, and 5,700 to 6,100 mAh discharged. If you have any sticks that vary greatly from these values, treat them with suspicion and mark them as problematic.

It is best that all the sticks in your pack discharge to about the same level. Very odd discharge characteristics in some sticks will drag down the better ones, causing the dreaded IMA warning light to come on sooner than it would otherwise. However, a 100 to 400 mAh difference will not present a significant problem to the car’s computer. None of the sticks will have exactly the same discharge value no matter what you do.

The End Result

At the end of a month of reconditioning, six bad sticks—out of the 20 in the pack—showed up, which explained a lot as to why the car functioned so poorly. Each failed stick was either excessively slow to charge or only at a partial charge after the machine said it was done. During cycling, poorly performing sticks will also get much warmer than correctly performing ones. Heat is one of the items that triggers the IMA warning light on the dashboard.

The next step was finding replacement sticks. I had to replace 30% of my battery pack and the most cost-effective way was to buy a junkyard battery pack and put it through the same charge-discharge process to find its good sticks. This took another 25 days, but was well worth the effort—the car now runs like new, gets 50 to 55 mpg on the highway again, and all the computer errors have vanished. I also have 12 good spare sticks for the next time I need to do this—probably in three to four years, judging by how long the original battery lasted before the computer errors showed up.

Failing IMA packs can also cause seemingly unrelated computer errors, like oxygen sensor failures and a 12 V battery error. The 12 V battery charges from the IMA pack through a DC-to-DC converter—my best guess is that the car’s computer uses it as a reference voltage to judge how well some of the car’s other sensors are working. In any case, all of the original error codes went away after the IMA pack was refurbished.


Michael Lamb s a professional handyman who loves tinkering with electrical things. After 10 years working at the Energy Efficiency and Renewable Energy Clearinghouse as a consultant, he retired to tinkering full-time.

Comments (170)

Michael Lamb's picture

Hi Swedeman, How are things working out for you and your car? Hopefully well. I have no idea if the comments field will be working in 2019. You can ask the editors of the magazine though. But I think things are still in flux there with the winding down of operations so maybe they have not decided yet. No one told me much but I know the old issues of the mag will be available online next year.

If any readers of my article would like to contact me I can be reached at michael 47 lamb at gmail . com

Scammers and spammers are not welcome! I say this just in case one of those finds my address and decides to abuse it. I deal harshly with abuse. It is a shame online conversations these days have to be thought of in this way.

Best wishes of the Holiday Season

Swedeman's picture

Dear Michael,
is the website closing with the ending of the magazine issues this year?
Is there a way we can keep in touch?
Thanks again and best wishes!

hybridbilsteknik's picture

Hi Swedeman you could also take a look at i am currently working on new battery pack for the honda´s
just give me a call or send and email from the form on the homepage and YES i am situatutad in Sweden :-)

Swedeman's picture

Impressive technical expertise in this column! Can I ask a more simple question regarding used Honda batteries. Honda in Sweden has not been able to give a good answer. My Civic 07 with about 140 000 mi need a new battery, Here are nobody that can recondition batteries and a new one costs nearly $3000, much more than the car is worth.
I can buy a used one from a crashed Civic 2010 (70 000 mi) for $1000 with one year warranty. However it has been stored on the shelf for a year and my concern is possible discharge and detoriation. My old one went bad after the car was unused for about 3 months… Is there more damage when it is unused in a parked car than being on the shelf?

Swedeman's picture

Impressive technical expertise in this column! Can I ask a more simple question regarding used Honda batteries. Honda in Sweden has not been able to give a good answer. My Civic 07 with about 140 000 mi need a new battery, Here are nobody that can recondition batteries and a new one costs nearly $3000, much more than the car is worth.
I can buy a used one from a crashed Civic 2010 (70 000 mi) for $1000 with one year warranty. However it has been stored on the shelf for a year and my concern is possible discharge and detoriation. My old one went bad after the car was unused for about 3 months… Is there more damage when it is unused in a parked car than being on the shelf?

Michael Lamb's picture

Hi, Re-reading your first posting I see I overlooked something important. You said your old pack went bad from sitting for 3 months. What makes you think it is "bad." More likely the cells have simply discharged and need to be recharged and the computer is not letting the pack turn on because the voltage is too low now. This is a common issue here for HCH's that sit months without running too. The official Honda fix was to tell you to run the car at 3000 rpm once a month for 3 minutes or so, before the pack gets too low. Not a lot of help for you now though. So let me say this, I have found that on the 2000-05 you can use a #12 solid copper wire to make a temporary jumper around the contactor the computer uses to isolate the pack when it gets too discharged to use. If the 07 is like this too you could try to "jump" the pack to a useful voltage again. Then the computer will continue to recharge the pack normally once the pack voltage is high enough to keep the contactor closed. On the cars I have done this too this takes a few minutes to happen. The process worked ok in the end, but you may need a friend to press the gas peddle as you hold the jumper in the right places. And you will need to find those right places too. It can also get a little scary since you are working closely with 180 VDC. There are also "grid chargers" for sale for long term storage, but you will need to have it installed and remember to run it at appropriate times (as well as disconnect it when you want to drive the car.) I am not sure if a grid charger with put out enough amps to recharge a depleted pack either. Something to look into.

Swedeman's picture

Thanks again! I had not heard before about the "Honda fix" to run the engine att 3000 rpm for 3 min - they forgot to tell me..
Anyway I tried it today and see- it worked also at this point and the IMA lamp is off. There is still the yellow engine indicator lamp on - but the car is running well for the moment. I will ask the Honda shop to turn off the indicator lamp (?) or tell me if there is a problem to continue driving this way. In the meantime I will try to find a cheaper used pack (with less shelf time than the current ones - 1 year since the cars were dismantled. Possibly also look to see if there is a recondition firm somewhere in Europe that has reasonable price and warranty for a refurbished pack. Too bad the auto industry could not agree on standardisation of a few
versions of battery packs that can be leased and/or changed in a "charge-station" for electric cars, like gas stations. Better Place was a try some years ago but it folded before being able to proof the concept. Interestingly there were electric taxis in London that had a battery change concept in 1905...

Michael Lamb's picture

Hi Swedeman. To read the check engine codes on any car just buy or borrow an OBD2 scan tool. I see cheap ones that will read and erase codes for less than $20 online. Make sure you get one that can erase codes, some do not. To be sure the Honda dealer will be happy to do this for you but at a high cost no doubt. If you see any codes you cannot find a reason for in your computer post them here and one of us will find an answer for you soon.

SK knows more about the 07's but it seems he missed a salient point that racing your engine at 3000 rpm got your pack to a point where you can at least drive it around now. So even though the recharge rate may "only" be 5-6 amps it was plenty to do the job in this case. I never did think too highly of the 20+ amps charging that the HCH1 dose, but then again it does the job well too. It is strange that no one else thought of it, especially the mechanic and dealer's shop people! Likely they just wanted to sell you a pack. Dealers here do such underhanded things too for the unwary.

Next I suggest you take your car on a one hour highway-speed drive to give the pack as good a charge as it can take at present. Do this after reading/ recording and then erasing the OBD2 codes from your computer. After the drive read any codes again to see what came back, if any. Chances are that if the car was working well before you parked in months ago it will be fine now too.

Those people in London may be of help, just far away. Better to deal locally when possible. Let us know how things progress.

S K's picture

The 3000rpm "technique" is only necessary if the car is sitting for extended periods, and it's not effective on HCH2 as it is on G1 Insight/HCH1. No matter what you do, you can't force the HCH2 to charge at more than 5-6A where the G1/HCH1 will charge at 20A+. A better technique for the HCH2 is to disconnect the 12V for 60 seconds, reconnect, start and idle charge until charging stops. Repeat a total of 3 times. In the U.S. the 12V disconnect necessitates re-entering the audio/nav anti-theft security code.

Before you reset the code or disconnect the 12V, you should find out why the CEL is on by checking the codes.

In 2013, 2006-2008 HCH2 battery failure rates were about 1 in 6 (5-7 years old)
In 2013, 2009-2010 HCH2 battery failure rates were about 1 in 3 (3-4 years old)

They increase the subpack spacing in the 09-11 packs to "improve cooling," and they made it far worse. They created more hot spots.

In light of that information, I would never purchase a 2009-2011 battery.

You can check the 11 subpack voltages at the orange plug. If they are less than 14.8V and if they vary by more than .05V, the condition of the battery is not favorable.

You would likely have better luck buying 2X CR-Z or G2 insight battery packs and swapping out all the subpacks. They have 8 each. You would have 5 left over. The CR-Z and G2 Insight have incredibly reliable subpacks due to dramatically improved cooling and lower utilization.

Peter Perkins is in the UK and has extensive experience with Honda hybrids

He has designed an OBDII based device that can read the 11 tap voltages from the pack to help identify problem subpacks. This is a far more effective tool in diagnosis than individual subpack testing as you get to see how they respond to the 100A discharge and 50A charge currents vs. the puny currents the vast majority of testers can muster including those used by Mr. Lamb.

Peter may also be able to provide you with replacement subpacks.

Michael Lamb's picture

I checked out Mr. Perkins site write up and what he has on youtube and he clearly says he is only knowledgeable on Insight1 and HCH1. He hand makes several homemade devices that a clever hobbyist may be interested in trying out on their HCH or Insight Gen1's, though at an extraordinarily high price in my opinion. (About $600 for the OBD2 thing you mentioned.) He also insists that only he will install this device on the car. Also since he seems to be the only one doing such modifications I strongly urge anyone tempted to proceed with extreme caution making such mods to their hybrids. He will also not sell sticks to the public, but only as a complete pack that he or his mechanic pal installs in the UK. This does not sound appropriate for Swedeman's problems at all. Please be much more discriminating when you post advice in the future here.

S K's picture

First, I do not make recommendations in which I'm not 100% certain is among the person's best options given the circumstances. The link provided was for background and contact information only. It is not particularly current. He is extremely active on and posts all of his activities there. I interact with him on a fairly regular basis.

Your issue is that you've used outdated information and incomplete research to draw a conclusion - possibly because you have an axe to grind with me for our past disagreements. I made recommendations/claims based on posts/comments/projects he has worked on within the last year. He personally reverse engineered the HCH2 data stream to discover the 11 voltage tap values. The device I mentioned is plug and play and requires no installation beyond plugging one in. I have the version for my G1 Insight, and it's worth every penny. He has offered multiple times on Insight Central to provide a wide range of services including replacement sticks, grid charging, grid charger installation, etc.

Swedeman has indicated a complete lack of support and resources in his area. Assuming a Stockholm to London drive, Mr. Perkins is 1200 miles away, and it may not be a great solution, but it's probably among the best. Regardless, now Swedeman can contact Mr. Perkins and decide what is best for him.

I stand by my recommendation.

Michael Lamb's picture

One other thing to consider is this: Shortly after the 07-2010 HCH had been produced Honda was being sued in class action lawsuits over these packs burning up (among other problems.) So a used pack of those years may have been a bad one too. Please keep that in mind when you make your choice as to how to fix your 07. A certified reconditioned pack by a reputable hybrid car pack refurbisher would be better than a used pack of unknown condition. Especially a used pack that costs 1000.

Swedeman's picture

Thanks Michael for advice! I agree about a reconditioned battery, the only problem is that there is no such
service in Sweden, Honda sold rather few of these models over here, and they stopped altogether with Civic hybrids
a few years ago - saying they will come back next year. But then they must have better quality and pricing or a leasing strategy -
if people here are going to buy them. It is too bad - it is a great car to drive and should run a few more years with reasonable battery costs - considering life cycle environmental foot print.

Michael Lamb's picture

Hi Swedeman I was wondering how things are going for you today. I hope your car is going again and acting right. If you come back here do not mind the argument we have going. Sometimes tempers happen.

Swedeman's picture

Hi again, just came back after driving forth and back to Gothenburg, one hour drive each direction. And in the morning
to my surprise even the indicator lamp was off when the car started in a very normal manner. It has behaved nicely all the day and also the milage was normal - same as the average the past 10 years. So again, thanks for the hint about the Honda fix, it should be printed in the manual... Actually I met a guy today that had worked at Honda several years ago and told me that they sometimes had participated in some "lean race" - driving very carefully and even drained the battery pack - and then used the fix.

My batteri problem really started last summer in south France, the car had been parked for a few weeks and it was very hot
both inside the car and outside. I tried to cover the back seat and shelf with reflecting sheets but still too hot I guess - and no use for a while. So the IMA lamps turned on and I became very worried about how to deal with this in France, looked on internet and found that there was a way to decouple the IMA and just run on the gasoline engine - but it was about 12 pages of instructions and nothing for me. I also learned that running with IMA lamp on would mean that the start battery got depleted, but that was simple to fix with a charger. After a while the IMA lamp turned off and it behaved rather normal again.
So I dared to drive back home, a trip of 3-4 days and it was OK up to the ferry between Germany and Denmark where suddenly the start battery was dead and I needed to boost it to get of the ferry - but no IMA lamp. Then it has been rather normal, a little instable at times according to the charging meter and now this week I had the IMA lamp again (temporary).

I appreciate all good advice, and particularly the Honda fix (3000rpm/3min). I have decided to continue for the moment with this (perhaps once a week if the car is used sparingly) and in the meantime try to negotiate a good deal for a used pack vintage 2007 with reasonable milage and little shelf time. If that does not show up in the next months I may have to contact UK and check out what deal I can get there. And save the old pack for possible refurbishing in good time. It is funny with old cars, sometimes they become "a close friend" that you hate to part from. Anyway I also bought a Ford Focus 2007 the other day for a spare and with a possibilty to hang on a trailor (a drawback with the Honda). I paid less than what they ask for a used battery pack and its running nicely. All the best from Swedeman.

Michael Lamb's picture

Hi Swedeman, That is all great news indeed. You are very correct, we do get sentimental about cars for some reason! LoL. Silly idea though since it is just a machine, like an expensive toaster. If no codes are in your computer then all should be well for a good long while again. Make sure your 12v battery is in good shape though. I replace mine every 5 to 7 years because in at least the 2000-2005 HCH and Insights a weak 12v battery will result in all sorts of weird problems in the car. Even if the battery can turn over the IC engine, errors can creep into the computer if the battery has a weak cell (not usually a bit issue for turning over a engine but a problem for the computer for a very "Honda" reason, no doubt.)

Heat and hot weather has always been the enemy of batteries. Still Honda did not do us owners any favors when it came to battery box ventilatilation. If you care to know what is in your battery box check out Weber University's shop class on hybrid cars at youtube. There is a professor taking it all apart and explaining what each parts does. From this you will see how tight Honda made everything to save space. It also shows something of why there is a heat build up problem too. Normally a well performing pack will not generate much heat, so Honda designed the ventilation with this in mind. But when cells get old (and abused a little) they produce more heat and that coupled with hot weather causes errors to creep in. I mentioned before that the 2006 and some of 2010 had serious issues with "cooking packs."

As a side note: Be careful of your 07 Focus transmission if it is a automatic. Ford had a lot of problems with the seals and solenoids in many. I know this from first hand experience unfortunately. Too expensive to repair so I had to sell it to a junkyard and got very little for it. I think getting stuck in snow is what finally did the trans in. But I also know the previous owner lived on the beach and probably got stuck in sand at times. I dont want to stray too far off topic here so I will leave this subject now.

Swedeman's picture

Michael, You are very right about the weak start battery - the first year (with warranty and free road assistance) it was so poor that I just depleted it in a few minutes along the road to speak on the mobile with the main lights on. About 10 similar incidents and finally I parked the car at the Honda shop with the warning blinkers on for some 10 minutes and it was out. Then they woke up and gave me a 70 Ah battery instead of the original, I think was 40. Since I have had no problems until the IMA went on in France last year and I needed to boost it to get going again. Your comment about later years battery packs that went on fire is a bit worrisome, particularly if you must be in a very hot climate - I thought it was only Lithium batteries that had such problems...

As for the Ford - it is manual shift so no worries.. Ciao!

Michael Lamb's picture

Hi Swedeman
I did not mean to alarm you about pack fires, rest assured they do not burst into flame like old Li cells can. When a NiMh cell gets too hot it mainly just vents a little electrolyte (think of it as the acid but it is a alkaline.) The worst you may find someday (hopefully never) is a bad chemical smell like bug spray in the car if the venting is large enough. No flames or fires if all the other IMA safety systems are working right. There is a mess to clean up in the battery area sometimes. Then the pack dies and it is time for a new one.

FYI. In the future when you need a new 12v battery, one hack I did to my HCH is to find the largest automotive battery that will fit in that spot. Fortunately since the HCH1 is based on a regular civic I can squeeze in a group 24 battery if I also cut away all the plastic spacers and straps Honda has around the 12v battery box. I needed to make a longer battery hold down strap though. I have never had a 12v failure again since even a small auto battery has hundreds of amp hours in it even if it does get a weak cell.

Michael Lamb's picture

For good or ill, the HCH is not being sold in the US anymore too. But I have seen the new Accord hybrid and it is very nice, just very big for a Honda, in my opinion. It uses liquid cooled Li cells which I am told are very reliable and the Honda techs I know have had no complaints about them. The main issues with these new hybrids they say is all the extra electronics in the car not working right (ie. blue tooth, navigation, voice activated things, etc.)

I suppose you could have a reconditioned pack mailed to you from the US or Asia, but the cost of doing that may be prohibitive too. Check out youtube, I am sure there are guys working on their 06-2010 HCH packs, maybe it will inspire you to DIY it.

Michael Lamb's picture

Hello Swedeman, I am not that familiar with the 07 HCH since Honda did some serious changes to the pack in 06 from what they made 2000-2005. However I can tell you that they were still using NiMh cells at that time. So you could use the same methods to bring a shelf-stored pack back to life. The only real challenge would be the differences in how the pack comes out of the car so you can work on it, and how the pack come apart. Starting in 06 Honda started welding two sticks together to form a "U" shaped module of 12 cells each. The chargers commonly used for deep cycling can usually only deal with 6 cells at a time without getting too hot. One way to get around this issue is to deep cycle half of the "U" configuration at a time. You just need to be VERY watchful of polarity when connecting the charger. Shelf stored or just left sitting in a wrecked car, the condition of any NiMh cell (unless already damaged in some other way) remains functional once deep cycled and recharged. $1000 sounds a little pricey for a used pack though. For a few hundred more you can almost by brand new sticks and go through the trouble of swapping out your old sticks.

S K's picture

Restarting at the top because the column is getting annoyingly narrow.


Pins 1 and 7 are the two at the driver's side.

You need to measure voltage from pins:


Polarity doesn't matter. I just "walk" the VM probes, e.g., 14 & 6, move 14 to 13, move 6 to 5, etc.

Pack master switch can be on or off. These sensing wires are measuring stick pair voltages at the orange end plate and in no way are influenced by the safety switch.

You can probe it unplugged, but it still needs to be the back of the connector. It's just a lot easier when the connector is being held in place by the plug.

Rynoflanders's picture


These are the values from pack A.

14-6 15.80
6-13 15.79
13-5 15.85
5-4 15.88
1-7 15.85
7-2 15.75
2-8 15.77
3-9 15.73
9-10 15.71

Do you think those values would code? The IMA light isn't on with the old pack or the new pack. However, I've read that perhaps I need to let the car run around 3500 rpm for an extended period of time in order for MCM/BCM to register the new pack and then perhaps I might at least get a code.

I still have codes U0110 and P0351. They appear quickly after each reset. The link you forwarded with the code U0110
could actually be what this car is suffering from. I believe the fuel in this car is about 2 years old.

S K's picture

Won't code due to resting voltages, but you have a spread from 15.71 to 15.88 or 0.17V. For resting voltages of a freshly reconditioned battery, that's pretty bad, and there's a good chance under load or charge, they diverge. If they held that 0.17V through most currents, that would be fine.

Would be interesting to hook a couple of 200W light bulbs in series, discharge to 120V and then swap them out for 40-60W bulbs. Check the taps again as it passes through 120V (might take hours)... might show that one or more taps are in really bad shape.

Did you check the grounds? ANY sign of corrosion is cause for replacement. I mean they need to look like pristine copper to be sure. Peel away some insulation to be sure.

2 year old gas? Ouch.

Rynoflanders's picture

I've unattached and cleaned all the grounds I've been able to locate. But there has to be more. So I've ordered a Honda Service Manual that includes a model specific electrical troubleshooting addendum.
Both codes (P0351 and U0110) appear instantly after each reset. I've attempted to swap coils around for code P0351 which should alter the code to P0352-4 but it remains P0351. So I believe the car has electrical issues outside of the IMA system that could be causing the PCM code U0110.

S K's picture

"Second, ground straps - the main (-) battery terminal and 2-3 other "ground straps" that connect the engine and transmission to the body. These often need to be REPLACED. Even if they look intact, they frequently have internal corrosion."

Rynoflanders's picture

I just wanted to get back you and thank you for your help. I purchased the OE manual and chased down the electrical issue causing P0351 and U0110. The main connector going into the fuse box wasn't making good contact. After I connected it and reset the codes the car started using the engine battery then began charging the IMA battery. I was able to drive it around enough this weekend to get the readiness monitors set and get the car smogged. So far the IMA light and check engine light haven't come back on.

I'm almost certain you've answered a "best IMA maintenance practices" question on another form. Could you recommend a site where you've posted that information? Again thank you for all your help.

S K's picture

There's no in-car "IMA maintenance" without added hardware. IMHO, your best option is a hybrid automotive prolong reconditioning system. It cycles the entire pack at once. Since you've done it at the stick level, and if your battery is in decent condition, you may only need something like a 24 hr charge every 90 days and a charge/discharge/charge cycle every 6 or 12 months - each of which will require about 10 minutes of touch time over the course of a weekend.

Michael Lamb's picture

I checked out that maintenance gadget you recommended and I DO NOT recommend it. The $618 it costs plus installing it is money much better spent on buying new cells. Also simply driving the hybrid highway speeds a few times a week will do much of what this gadget will do anyway. Most people never seem to do more than start and stop the car and so draw down the cells. Also, just like grid chargers in general, people experiencing IMA pack problems will get nothing of real value from gadgets like this. Please stop recommending people buy things when you post here. Thanks.

Rynoflanders's picture

So I followed this process and I have a couple questions.

1. Should there be 144V+ at all times at the battery pack terminals? (with the breaker ON if the battery is charged)

2. Does the MCM trigger the final "ON" for all the voltage to pass through to the terminals?

Ultimately, after refurbishing the cells I have 157 volts when probing the negative terminal and the bottom left battery bolt that is covered by one of the grey plugs but I have no voltage at the connection terminals. I'm having issues with the normal car battery and I believe that it might be effecting some of the electronics for the IMA battery.

S K's picture

I'm sorry you followed this process. Unless you replaced the defective stick(s), it was likely wasted effort. You have likely made a mistake in the reconditioning process, made an invalid assumption about what is acceptable, or you have made an error in the pack build.

1. Yes. If you ever measure a NiMH cell at 1.2V at rest, it is completely depleted of usable charge. 1.2V is a NOMINAL voltage - the voltage used for power and circuit calculations. You will never see that at rest in a healthy cell unless it's completely depleted of usable charge.

2. Essentially yes. Once the car has confirmed the pack is within parameters, the relay is energized and connects the battery to the car at the main terminals.

157V is not outside expectations; however, it tells you nothing about the health of the battery pack. You could have a single dead/weak/shorted cell that influences the voltage by 0.6-1.2V, which is outside operational parameters, and the relay won't energize. The car monitors the pack every 12 cells via the grey/orange connector that connects the end plate on the junction board side to the computer (MCM/BCM). If these 10 different voltages are outside of a relatively narrow range, the car codes.

First, your 12V MUST be healthy. If you aren't 100% confident it's in full working order, replace it.
Second, ground straps - the main (-) battery terminal and 2-3 other "ground straps" that connect the engine and transmission to the body. These often need to be replaced. Even if they look intact, they frequently have internal corrosion.
Third, once the above is sorted, you should be working to the error codes given. Period. If your CEL and/or IMA lights are on, you should be pulling codes and working to them.

Once you've executed the 3 things above, you should check the voltages at the BCM connector:

If these vary by more than about 0.1V at rest, that's your problem. The diagram is for the back of the plug. You check it with it plugged in and probe the wires as they come out the connector.

Good luck.

Rynoflanders's picture

S K Thank you for your response.

As of last night I've installed a new 12v battery and pulled the codes.

P0351 - Ignition Coil A Primary/Secondary Circuit Malfunction
U0110 - F-CAN Malfunction Battery Condition Monitor Module-Motor Control Module

I still need to double check all the grounds.

I'll use the diagram you provided and record all the values. It'll be about 2 days time.

Thank you again for your time.

S K's picture

Not familiar with those codes, and I don't have the HCH1 service manual.

For U0110, try this thread:

HAH is highly similar to HCH1.

Rynoflanders's picture

So I've recorded the voltages in 2 packs. They vary greatly. The first one (pack A) contains the sticks I cycled and reassembled. The second (pack B) hasn't been unassembled (that I know of). Both packs came with the car. The car also came with a grid charger.

Note: I have no IMA light on in the dash or bars on the "IMA" energy read out.

Pack A
1. 94.6
2. 62.8
3. 31.3
4. 92.5
5. 108.2
6. 139.2
7. 78.7
8. 47.1
9. 15.6
10. 0
11. blank
12. blank
13. 122.2
14. 153.3

Pack B
1. 43.3
2. 29.1
3. 14.8
4. 43.3
5. 50.3
6. 64.4
7. 36.3
8. 22
9. 7
10. 0
11. blank
12. blank
13. 57.5
14. 71.6


S K's picture

You didn't interpret the diagram correctly, or you're not working with an HCH1. If an HCH1, you likely read it backwards. Good voltages should be in the 15-16V range, and they should all be extremely close to one another. Voltages should be read to XX.XX accuracy.

Rynoflanders's picture

2004 Honda Civic Hybrid CVT
Even if I somehow read it backwards the values of the charged pack all exceed 15V.
I suspect that because it's in series the individual wires relay a sum voltage given the number of cells it's measured. Either way my 153.3v should equal 7.66v per stick and add up consistently along the way. Instead my 15.6v from socket 9 means my 2 stick average is 7.8 and my final voltage should be 156v. So the pack is not balanced.

I'm going "soak" pack A and re-check all the values to see if they balance out.

S K's picture

"they should all be extremely close to one another" - this is the most important thing by an order of magnitude. Any belief that a large voltage range is acceptable is complete folly. A good workable pack will have a the 10 resting voltages within about 0.06V of each other - especially if it has been successfully "reconditioned". 0.1V is likely a short-lived pack (6-12 months) 0.2V is likely a 3-6 month pack.

Average stick voltage of 7.66V is meaningless.

If you take your readings, sort by value and subtract the prior while cutting out the 2V outlier:


The above indicates a completely worthless pack or garbage data.

You're asking for advice. I'm giving you advice based on 4+ years of testing more than 5000 sticks/modules.

If you're an "askhole" - someone who continually asks for advice/input and then ignores it, I'm not going to waste my time with you.

You need to properly measure your 10 tap voltages to XX.XX accuracy. The picture of the plug is clear with the release tab depicted. You have to translate the pin values according to their label and probe it from the back of the connector while it's pluged into the MCM/BCM. Doing anything more before gathering this data just masks the actual condition of the pack. If you've recently reconditioned sticks, and your resting tap voltage deviations are greater than about .06V, you likely have marginal/bad sticks in there.

I assume "soak" means you're going to charge the whole pack at < 500mA for many many hours. If you insist on doing that before gathering more data, you're just prolonging your pain and increasing your uncertainty, UNLESS...

Assuming you "reconditioned" them sufficiently to reclaim any lost capacity due to voltage depression, if you want to get maximum results for minimum effort, do this:

1) Charge whole pack at < 500mA (350mAh preferred) for 24 hours or until voltage fails to rise by 0.1V for 4 hours OR if the temperature of air exiting the pack (with forced cooling) is > 95°F (assuming ambient is about 75°F)
2) break the pack down and let it sit for 7 days.
3) Measure individual CELL voltages within each stick to 1.XXX accuracy (yes, 120 measurements). Truly healthy sticks will have cell deviations less then 0.010V. Workable ones will be less than 0.030V, but they will likely be short-lived and require grid charging 1-4 times a year.
4) Attach the aluminum spacers with long bolts onto the end of each stick and use a 12V 100A load tester (Schumacher BT-100) to load the stick for 15 seconds. Record pre-test voltage AND loaded voltage immediately before removing the load as reported by a separately attached voltmeter (tester VM is impractical). Repeat for all 20 sticks. cool the load tester in forced air for 2 minutes between tests.

Tabulate the cell voltage data and the load test voltage data. The bad sticks are the outliers.

Rynoflanders's picture

"You need to properly measure your 10 tap voltages to XX.XX accuracy. The picture of the plug is clear with the release tab depicted. You have to translate the pin values according to their label and probe it from the back of the connector while it's pluged into the MCM/BCM. Doing anything more before gathering this data just masks the actual condition of the pack. If you've recently reconditioned sticks, and your resting tap voltage deviations are greater than about .06V, you likely have marginal/bad sticks in there."

I did this multiple times with both packs. Both packs plugged in and ON. The picture is very clear. Hence the reason I can't see how the voltages vary so much yet across both packs. Does the key in the ignition need to be ON? Most of the voltages were to high to get XX.XX value. 20+v on my meter reads XXX.X.

I'm back pinning the connector that is attached to the board in image you sent while it is connected to the MCM/BCM and the pack is on.

Have you ever pinned the connector while it hasn't been connected? I get the same values whether it was connected or not. The key was never on in either situation.

Overall, I appreciate your help. I'm not trying to troll you. Either I've missed some very basic (and I can't see how) or those are the values I'm getting.

DustyB's picture

Hey Guys, I am confused with all the comments, is the above method the best process for reconditioning these batteries?

I have an ICharger 4010 DUO, what would you recommend as the best setup?

What Charge current should I Charge at?
Discharge Current?
Wait time?

my charger works with C Rates, what do you recommend this setting to be????

Any help is much appreciated Thank you!!!!!

DustyB's picture

Thank you very much everyone. is it bad to cycle the cells at a very low rate? I have been doing it because I read somewhere else that it helps revive bad cells. .1 or .01 A

S K's picture

If you discharge below 1V per cell, you should do it at a very low current (0.4A or less).

If you charge at less than 1C, the -dV cutoff may not occur. You need to set a charge termination safety by temperature, capacity or time.

The only reason to charge at very low rate is to balance the stick. You should be able to charge an EMPTY stick at 0.65A for 16 hours. Terminate at 10,400mAh input, or 40°C. It likely won't trip -dV cutoff, but it might.

Not sure about your specific charger, but many iCharger models have a "Formation charge" or "Form chg" program. I highly recommend that. You set it for 6.5Ah and 6 cells. It will charge at 6.5A for 1 hour or 6500mAh input. It will also reduce current to keep voltage from exceeding 8.88V/stick. It will also terminate once the current drops to a certain level (not sure what it is -something like 25-50% of the starting current). Once the main charge terminates, it charges for 2.5 hours at 0.65A to top it off and balance it.

Low current won't recover a stick any better than high current, however, low current charges are good for balancing, and low current discharges are good for discharges below 6V/stick.

While I said "good" several times, it's context specific. No process will recover a stick with a failed cell, excessive self-discharge or high internal resistance.

Highly likely that your efforts will not pay off, but good luck.

DustyB's picture

Help please.

S K's picture

6.5A charge
20 minute wait
20A discharge
Do NOT exceed 1C on charge

Keep your expectations VERY low. Any stick that starts out at less than ABOUT 7.5V after sitting for a week is likely going to be a problem.

FWIW, Orange sticks are old G1 Insight sticks. The yellow sticks are the newer HCH1 sticks. The orange sticks have higher internal resistance by design. If honda has release a "new" orange stick, I'm not aware of it.

Michael Lamb's picture

Hi DustyB. Since SK didnt answer your question I felt I may as well do so. SK does such a fine job of it I feel it best to let him run.
When cycling this type of cell it is best to set your machine to as high an amp setting as it can handle. Use a fan for cooling and keep an eye on cell temps. You cant really hurt the cell by going too fast. Believe me I have tried to and the worst that may happen is some cells might get too warm to keep your finger on. If that happens replace that stick as it has too high a resistance anyway and will not work well in the car. Two or three charge and discharge cycles should do the trick, if the cells are still fit to use in the car at all. However I got to tell you that if these are the original yellow sticks they are probably not worth the effort these days. Cell chemistry does wear out eventually. I have had better results with the next gen orange sticks, but many of those aren't much good either. Let us know how things turn out for your project. Thanks.

S K's picture

Mr. Lamb has given advice inconsistent with reasonable scenarios as thousands of Honda IMA owners grid charge on a regular basis with no issues.

This is not a PTC problem, this is a cell vent problem. The cells have vented allowing conductive KOH electrolyte to short the PTC circuit, and in many cases, this does cause BCM failure.

P1433, P1447, P1449 and P0A7F are all common battery failure codes and do not indicate leaking cells. A P1444 is indicated when a leaking cell short the PTC circuit and warrants the steps presented by Mr. Lamb.

So, if you have a P1444, do not attempt grid charging. Pack must be removed and disassembled with extra care because there will be voltage where there shouldn't be.

Excessive grid charging of the early batches of Chinese sticks introduced by Hybrid Battery Repair with possible use by other battery builders can cause sticks to grow in length and fail at the seal crimps, or their vents don't function at all. It was an early defect that is showing up with some regularity on the older aftermarket batteries but was corrected shortly thereafter.

Excessive or improper grid charging on ANY pack can cause this failure; however, it is a very low risk occurrence. An HV leak is more likely to occur during the IMA recalibration where the car force charges a full battery at 4-5A until it figures out it's full.

If grid charging is necessary, your battery has FAILED, and you are on borrowed time. If you are grid charging more than about once every 3-6 months, your battery is on its last legs, and you are just nursing it along. You should expect it to get worse AT ANY TIME, including the leak risk, even as the vast majority of grid charger users experience years-long life extension of their IMA battery.

Removal of the PTC strips is an option, but strips need to be completely removed, which involves cutting and removing the shrink wrap and re-shrinking the sticks (sticks installed in the case without shrink WILL cause the pack to catch fire). Furthermore, the PTC circuit must be closed with a 20-30Ω resistor.

Michael Lamb's picture

All good advice SK, as usual. However P1444 is not a total indicator of the issue. There was no such code present before I started in on the pack I worked on. Just the general P1600 and P1449 and the pack being totally discharged to almost zero volts (very odd to find.) Your advice on not using a grid charger more than once in a great while is excellent. At best I found them to be a not particularly helpful "band aid," generally I find them to be a waste of money. Better to spend the several hundred dollars they cost buying new sticks.

Michael Lamb's picture

IMPORTANT UPDATE: If you have a Grid Charger (any brand) installed on your Honda Hybrid STOP USING IT! At least until you are certain you do not have a short in the PTC system inside your pack.

Recently I have been reconditioning a 2003 Insight battery pack for a friend. During the initial disassembly I found that 7 of the PTC strips (Pack Thermal Continuity) had shorted against the positive end of the 7 battery sticks they were attached to. There was significant corrosion and the cells had vented a bit at those terminals, which made it easy to find the problem locations.

I was told that for years this particular pack had a self discharging issue (which was why the owner added a Grid Charger). I believe the grid charger contributed to the destruction of the Battery Control Module, and venting, by constantly keeping the cells charged and the shorted energy making ground through the BCM, wrecking it.

So disassemble your pack and check that you do not have any PTC strips shorted to any cells before you install or use a grid charger!

Also it may be better to simply remove the PTC strips totally since Honda issued a bulletin (TSB) in 2012 which disabled the PTC system anyway.

Michael Lamb's picture

Like I said before, a picture is needed. You are still missing much of what I have done. NASA theory is fine. But it doesnt really apply well on this car. I will look into posting a diagram of what I have made. FYI, everything I mentioned before is working fine on my '03. All summer long no problems, 59 MPG average for the last 500 miles. Cool to the touch cells, less than 80F at all times during the past month. Plastic baffles are long gone too, the fan stays off pretty much all the time even with the resistors. Looking forward to really hot weather! You really need to try things before you condom them SK. More on this thread next summer. Case closed. Thanks for the rant.

S K's picture

Going back to the top so our columns are more than 3 words wide.

Unfortunately, you haven't PROVEN anything beyond, "it will work for X time frame in Y climate" where X is however long you've been driving it that way and Y is whatever your current climate is (which I suspect requires very little cooling - if any - this time of year). You have no objective before/after data showing the pack is any cooler or that it will last longer. You didn't conduct a temperature survey of the pack before or after the modification, so you can't say the cells are any cooler. Disagreeing with changes made for change's sake is not "defense" of a bad design. Just because you change a design doesn't mean you've made it better. When I can point out that you've made poor judgement based on incorrect assumptions, you've violated good engineering practices, ignored 100+ year old airflow/cooling data, and disabled the few good things about the cooling system, it's a comment on your modifications - not the original design.

As I have stated a couple times now, simply spoofing the fan to think the pack is hotter than it is would be vastly more effective than what you've done.

If you think your 3 sentence description of the modification is adequate for anyone, you are mistaken. If you are going to encourage people to cut holes and completely mangle their cooling system, pictures are in order.

Your description gives me a good idea of what you've done, but it only reinforces my concerns. You've made your battery cooling completely dependent on orifice size, and if you haven't sized it right, there's a good chance you're effectively bypassing the battery. Rather than pulling ALL of the inlet air through the battery, you are likely pulling less than 1/4 of it, so for a given fan speed, you are moving less air through the battery than before

What you've certainly done is ensure that you're just churning hot trunk air through the IPU instead of drawing from cooler interior air (that you can actually cool via the A/C).

What you should have done is installed a CPU chiller in one of the A/C vents, run the chilled coolant to the back with tubing and install another heat exchanger in the battery inlet duct. This was demonstrated to be astoundingly effective on an Insight with sustained 60A discharging and charging (issued by manual commands through IMAC&C).

Again, anyone reading these comments, except for #4, PLEASE do not make the modifications encouraged by Mr. Lamb. There is no objective evidence that they are beneficial in any way, and all but one modification he has made is a negative either for air flow or heat transfer. You can't add up a bunch of negatives and come out positive.

1) Removing baffles: Less airflow in contact with cell surfaces. Less surface contact means less heat transfer due to forced convection. Less heat transfer means hotter temperatures. Increasing airflow can't overcome this. Imagine cutting the fins out of our radiator - you wouldn't expect it to work better even if you moved more air, would you?

2) Use of trunk air for cooling: Trunk air can't be cooled effectively. The fan exhausts into the trunk, so cooling the battery actually heats the inlet air. Since there's no longer any pressure differential, the trunk won't dump as much hot air overboard. You're just going to keep churning increasingly hotter air through the pack. The claim that later model HCH had more openings is completely incorrect. They actually reduced the number of openings for better sealing going so far as to install the fan INSIDE the IPU.

3) Reversing flow through the battery and tapping into the MCM duct: The MCM exit duct holes are larger than the battery inlet opening by about 3:1. This was done to ensure that the exit didn't limit the inlet. Now that the flow is reversed, the fan is sucking on the MCM holes and the battery inlet hole. Since the MCM duct holes are larger, it will pull correspondingly more air through those holes rather than the battery (regardless of the position of the bottom hole). Less air through the battery = less cooling

4) Not a bad idea. The only downside is that the car limits performance based on temperature, which could limit assist/regen availability sooner.

currentchallenged's picture

I have one of the 2003 HCH. I had purchased a batter 2 years ago from a junkyard. Now it is time for emissions again, and the Check Engine light is the bane of my existence. I am in Phoenix, AZ and could use some insight. Would it be better to by a full battery, purchase sticks from China, or try to recondition what I have. I read most of the posts here and Steve always comments that the last option is kinda pointless. I don't have a problem replacing sticks, but I know it's time consuming. I guess a forth option would be to get a different car, but I like my hybrid plate during rush-hour traffic.

For the record, I have a check engine light, IMA light, and over 220k miles.

Thanks in advance for any suggestions, pointers, and other information.

S K's picture

I feel your pain. I'm in Phx too. Lots of folks with IMA battery issues and emissions. I'd you didn't have the HOV plate, I would say just drive it to the salvage yard. I would recommend a reconditioned or new battery from Bumblebee. Anything else represents either wasted money or time. Obviously, you should get your codes read to ensure there are no other issues. I would expect you're due for a new cat soon. Good luck.

TomG's picture

I am working on reconditioning my 6 cell sticks for my 2006 Honda Civic Hybrid. To recondition, I expect that my minimum voltage should be set to 4.8v (6*.8) when I do this, on my third cycle, I get a discharge reading of 1062, and a charge reading of 1133 on my TB6B device. The entire process of three cycles took about 10 hours. My initial reading of voltage on the charged battery was 8.28 volts.

Any help to get this correct would be appreciated.

ralphsworld1's picture

Michael or anyone else that has any insight. I have purchased an original core battery for a civic hybrid- I work at the dealership and when we replace a battery with a CA4 (usually the batteries we pull out are CA1's but the one i purchased is an original with no triangle sticker), what exactly is the software making different? I assume the charge rates. When we switch the batteries we have to update software otherwise the MCM doesn't recognize the new battery and will still display an IMA light after the replacement even after clearing everything out. The software update is the only way to get everything to work properly. My problem here is if I purchased an original battery am I able to mix the cells with a CA1 or a CA4 for my recondition? I assume they are different sticks and the hondas dont take well to mixing and matching sticks.

Let me know any advice or information on this... becuase through this whole forum nobody talks about the different model batteries and I am just wondering if anyone knows the difference between them and the software. I plan to start my first recondition next week when the battery comes in. I currently own 3 civic hybrids and have become obsessed with hybrid batteries. One has a CA4, and two have CA1's. Is this core i purchased going to be useless?

S K's picture


I can't comment with regards to the CAX specifics; however, I can say with 100% certainty that there are not differences in the CELLS.

This is how I understand it - it may be wrong, but it works:

1) 2003-2004 HCH battery packs were built with PTC strips on the Sticks (presumably CA1).
2) 2004-2005 HCH battery packs were built without PTC strips on the sticks (switched mid-year 2004, presumably CA4).

If you have an 03-04 with PTC strips and the "old" MCM, you either need PTC strips OR a 30 Ohm resistor spoofing the MCM or the patch.

If you have an 04-05 without PTC and the "new" MCM, you either need NO PTC strips OR you need to cut the circuit so it shows open circuit - per the Honda TB that shows you cutting an inch out of the red wire.

Sticks from either may be intermixed.

In other words, sticks don't matter... the PTC strips that are or are not present on the sticks and the PTC circuit are what matter.

Where are you located?

ralphsworld1's picture

I am in Phoenix AZ and have seen people need to replace their batteries on a yearly basis with our heat.

OK So we are getting somewhere. When we do a battery pack replacement at the dealership the techs aren't aware of any of these changes. They run new software according to the battery we put into the vehicle in HDS. So what I am assuming from what you tell me we are just changing the MCM's programming to look for or not look for the PTC circuit. You said theres a bulletin about clipping the PTC circiut ... do you have that bulletin number by chance?

In other words a battery pack that will work in an 03 will work in an 05. Just need to run the software applicable to that battery. There are like 5 selections in HDS (honda diag software) that cover the original to each time honda changed the batteries. Theres a chart that you take the triangle sticker code and refer to a part number - I can't remember the models there are but CA1 was being used only five years ago and CA4 is within the past 3 years as the most current battery. When I have a minute at work I can pull it up on HDS and tell you all of the battery codes.

So the real question is with this original battery core i purchased from a guy in Colorado (we never see the originals anymore here in phoenix) that probably has PTC's on the sticks; I will have to either add PTC's to the sticks that come out of the CA4 and CA1 or buy sticks off ebay with PTC"s already on them? I assume all of the cells need to either have them or not have them seeing that this seems to be the only physical change the software accomodates..... you say the "patch" you mean the software? this makes sense - it shows how all these shops are doing these battery swaps without having access to HDS (only honda dealers have access to the updates)

Michael Lamb's picture

I wanted to mention that I have determined the Honda ventilation design for the battery box is garbage. I suggest that when reconditioning your packs in the future you do the following to improve airflow over the cells:

1) Remove all the plastic baffles: There are 6 screws that hold them in the pack frame. After removing them all, you will need a large flat screw driver to pry out the baffles. They simply pop out.

2) drill a 3 inch diameter hole in the bottom of the battery box for fresh trunk air to enter. Directly under the pack is best. Later models of HCH had lots of vent openings all around the pack. More moving air is always better where cells are concerned.

3) Remove the foam plastic air duct from over the pack (this duct is inside the trunk) and connect it to the plastic duct for the motor controller next to it. Drill/cut a large connecting passage between them. Make air tight connections.

4) Add a 200 ohm resistor to the blue sensor wire (common wire) inside the white sensor connector (located on the pack control end plate top left, between the two grey connectors.) Adding the resistor will make the battery box fan turn on sooner. Right now it doesnt turn on until it is around 120F.

Of course in AZ everything gets hot as blazes eventually so doing all this will mainly just postpone cooking the cells.

I have done all this to my HCH and all worked well.

S K's picture

Michael, Your initial conclusion is correct; however, 3 of your 4 recommended courses of action are not at all appropriate.

1) absolutely do not do this. Educate yourself about the aerodynamic characteristics of of a cylinder, and you'll see why the baffles are present. You have severely compromised your pack's ability to cool the cells and have created hot spots. You are dealing with case 4 for the top sticks and case 3 for all other sticks downstream:

With the baffles in place, the airflow is directed AROUND the cylinder increasing the surface area over which it is flowing instead of allowing it to detach.

2) You realize that the 2006 HCH and up have the WORST hybrid batteries ever made with the WORST cooling characteristics, and I question the claims you have made about the openings. I owned 2X 2006 HCH, and I don't know what you're talking about. You are suggesting that it's better to pull air in from the trunk than the air conditioned interior of the car? Why?

3) I can't even think why this would make sense.The way you describe it makes it sound like you've actually bypassed the battery with the cooling air flow. You know the IMA fan dumps the hot air into the trunk, right? You really want to suck that back in to the IPU?

4) This is viable; however, you are incorrect. The fan turns on much earlier than 120°F, but you can't hear it on the lower speeds unless you're paying close attention or are monitoring it with HDS. If you are 100% certain that your fan isn't coming on before 120°F, then something is wrong with your cooling system.

I would discourage anyone from executing ANY of your recommendations. You have no data to support that you have made any improvements whatsoever. The only thing you can conclusively say is that your battery still appears to work. You have no idea if it's running hotter, or if you've created hot spots within the pack (you have). You have deliberately made a modification that compromises the airflow around a cylinder and reduced the surface area in which the cooling airflow is in contact, thus adversely impacting cooling.


Michael Lamb's picture

Hi Sk
In the perfect world of NASA space travel I agree that their data on air flow is correct. However in the reality of dirty, vibrating, hot, dusty, cheaply manufactured electronics, automotive world things work a bit differently. If the NASA facts worked the way Honda wanted then there would be NO issues with heat in the cells. Obviously the Honda design is missing something and is flawed. We have been messing around doing the same things with these packs for years with the same failing cell results now havnt we? Time to try other ideas.

Let me explain more on why I think removing the baffles is worth doing: True the turbulent air flow is better with them in, AS long as the air is MOVING. As soon as it stops flowing latent heat in the cells quickly builds up, because the baffles act as insulation holding it in. With the baffles out two new sources of heat dissipation occur: Some convective air flow and radiant heat flow. (I also take out the foam panels in front and behind the pack to increase the radiant flow.) I have personally seen a 5 degree drop in cell temp after I made these changes. (yes I put a thermometer probe inside the pack for this.)

Also, Honda's design tries to pull warm air down into the pack and then out past the motor controller. Bad thing about that is that warm air is more buoyant and doesnt flow down worth a damn without a lot of force dragging it along. Also the box must be AIR TIGHT for this to work right. I seriously doubt this is the case in most HCHs. So what happens when the fan stops? All that hot air gets stuck around the cells. So I modified the plastic ducts over the battery box so the warm air can naturally flow up towards the inlet of the fan as the car sits. The large hole in the bottom of the box is part of this. Of course I would like to take inlet air from someplace cooler but that was not too practical in a car. I thought of making a thin duct under the seat for this instead. The coolest air being on the floor. The trunk was more practical to do. Also think on this: Honda is taking air from the rear deck, right in front of the big ,glass, very HOT window. Care to guess how hot that air gets in direct sunlight anyone? Ever mess around with a solar hot water panel in sunlight? It gets over 200F next to that glass. I measured it once. Ouch. Also not a lot different than trunk air temps.

Another thing to think on is how the chemistry in the cells react to staying hot longer as they sit idle. From my days doing crystal growing I learned that any crystal structure needs to have a slowly reducing temp for the crystals to have the time to form. In a NiMh cell we have problems with nickel crystals forming. Cooling the cells faster helps slows this to some degree. Keep the air moving, even warm air draws off huge amounts of heat as long as it is moving. Add some radiant cooling and we might be getting somewhere.

Maybe my fan isnt working right, however I have seen the identical issue in my other 03 and have changed the fans 3 times. Also the fan controller checks out and it works correctly according the the Honda tech I had. I suspect that your fan runs on low a lot since you are in a hot place, in Virginia the fan stays off way too much for my liking. Thus adding the resistor to force it on at lower temps.

S K's picture

It's completely unreasonable for you to dismiss a phenomena because you think it only applies to NASA and space. That phenomena was discovered decades before NASA existed - even before the Wright brothers flew. All the reasons you give are just red herrings presented to dismiss science in favor of your "instinct".

What you don't understand is that in your configuration, you could move 20X the air through the pack, but you won't get any more cooling because that air only contacts a very small portion of the cells. Forced convective heat transfer is highly dependent on surface area. You're familiar with radiators, right? Why do they have fins between the passages? Because more surface area yields greater heat transfer. What you have done is analogous to cutting all the fins out of your radiator.

Furthermore, you've confirmed my suspicion. You have completely crippled the HCH1 cooling system.

You appear to understand it, but the choices you made suggest otherwise. The HCH cooling system works like this: The IPU fan is located in the trunk. It pulls air from the IPU cavity, and it exhausts it in the trunk. Air is drawn through the IPU cavity from vent/duct in the rear deck. This pulls the air in through the battery, into the IPU cavity and out into the trunk. By opening a hole in the bottom of the IPU cavity, you have BYPASSED the battery with the incoming air.

Your assertion about the buoyancy of air and it's strength is absurd. Get your pack good and hot and put a piece of paper in the path of the exiting convective airflow. It won't even move the paper - yet you see that as "a lot of force." Furthermore, the 2004-2009 Prius is a down-flow pack in it's configuration... In comparison, the Prius has zero cooling issues compared to the HCHs. Prius packs last a long time here in Phoenix. Also, the blower for the Prius is PUNY compared to the leaf blower of the HCH.

You understand that once you park the car, you are no longer generating any heat, right? You are seeing nothing more than heat soak - the heat at the center of the cell migrating outwards towards the surface and becoming more uniform throughout the cross section. Probes are at the surface. When you see the temperature rise after parking, you are seeing the surface temperature. The average temperature of the cell is actually LOWER when the probe reads higher because the core of the cell is now significantly cooler having transferred its heat energy outwards.

You may have hastened the rate of cooling after the pack is no longer generating heat, but you've done so at the expense of keeping the pack cool when it is generating heat.

I can promise you that your configuration wouldn't last a single Phoenix summer.

Unfortunately, you've convinced yourself that you know more than engineers or aerodynamicists, so I doubt I'll ever convince you of the crime scene you've created. My only hope is that someone reading my response will be discouraged from pursuing the same modification and ruining their battery as a result.

Michael Lamb's picture

OK, You have made your view. Let agree to disagree. You keep on replacing failed sticks. I will keep on using mine with my modifications. We will see who does better in a couple years, Ok?

S K's picture

Michael, I haven't made my view. I've presented clear and factual evidence that you've done great harm. Your "agree to disagree" is the stance taken by someone who can not respond to facts with a valid argument. We don't just disagree, we disagree violently. You have actually sabotaged your pack's cooling. I encourage you to assess the amount of air you have flowing through your pack. I'm not at all convinced you're getting ANY flow through the pack based on your description of the modification. It sounds like you're just churning air around the trunk and through the IPU. It wouldn't be a fair comparison in any regard Phoenix makes VA look like a winter wonderland, and I'm not foolish enough to continue operating an HCHX in Phoenix. I still have my two Insights, but those are a different beast.

Michael Lamb's picture

You have made your point very clearly. Clearly you do not understand what I am doing. I wonder if you even understand this car as much as you lead the other readers to think you do too. You say the Honda design is bad and then you defend it with great vigor. You dismiss practical ideas that I have PROVEN work at least here in Virginia and then continue to make insults. Unless you have done as I have been doing YOU are the one who is BLIND.

Michael Lamb's picture

Besides these car are so old now that they are worth experimenting on some. Nothing to lose. I pick them up for less than 1000 because everyone is afraid of the IMA pack as well as the CVT trans. So live a little. Make some changes. I will even post a diagram so you can have a picture to follow, since you clearly did NOT really read or comprehend what I wrote earlier. Maybe a picture would help.

S K's picture

It's small world... I'm guessing your name really isn't Ralph (Mark?), and you recently had a conversation about hybrid batteries with some anonymous guy on Craigslist? If your name really is Ralph, disregard... :)

It's easier than you propose. PTC strips or not on the sticks doesn't matter. You need to present a spoofed 30 Ohms (simple 1/4 Watt resistor) to the old MCM or an open circuit to the new MCM.

In short, you will be able to make the guts of that core battery work with any other 03-05 pack provided you respect the above.

I can't find the one that patches the HCH1 and instructs cutting of the wire, but the wire is discussed in service bulletin 12-048.

Michael Lamb's picture

I just got involved with another pack refurbishing (actually two at the same time): When opening up the first pack I noticed the cut PTC (red) wire you mentioned here. My first thought was "I have been sabotaged," and after finishing the first pack and putting all the stuff together again like I thought it should be the car ran great, for about 10 miles, and then threw some new codes at me including "communication error." I do not recall the code now. Is that what happens when you connect the PTC again on a MCM that has had the updates? Probably why that was was cut, huh? Of course the car stopped running when the 12v battery ran out of juice. I was very surprised to say the least--until I read your posting on the PTC mods. I am going to try those changes later and see if things get back to what I was wanting. Thanks for the info, keep up the great work! BTW the local Honda dealer had no clue what I was talking about when I told him about the cut red wire! Neither did Honda America in California when I called them. Ugh.

S K's picture

You need to fully assess the codes before you do anything. Your lack of specificity makes it impossible for me to offer anything beyond that. The car is telling you what's wrong with it. You need to act accordingly. The fact that it ran for 10 miles without codes suggests it as nothing to do with the PTC circuit as those codes present immediately. If you can provide me with ALL the codes it's reporting, I might be able to offer guidance.

Michael Lamb's picture

I found that there was a failed relay. Problem solved. The new reconditioned pack operates wonderfully now. All green bars when braking and lots of blue bars accelerating. No IMA light for 500 miles now. I am lovin' it!

ralphsworld1's picture

it is most definitely is a small word. Ralph is my bulldogs name.

I think the HDS updates take care of the resistance change for us - no physical changes like this need to be performed at the dealership when we switched over to the newer style batteries ....just the software updates. sound right? That is how you do the swaps without the software - which didn't make sense to me before.

thanks for the bulletin number. I'll look around for the other bulletin.

S K's picture

Now you have my initials... :)

The HDS update REQUIRES cutting of the red wire if it's an old pack with PTC strips via the SB I can't find (I think I have it at home).

The old version NEEDS about 30 Ohms on the circuit (indicating good PTC), or it codes.
The new version needs OPEN circuit, or it codes.

ralphsworld1's picture

ok so just a slight change to the junction boards. as long as the junction board in the car stays in the car then no physical changes should have to be made right?

S K's picture

heh... we keep cross-typing...

I can promise you that the core battery you purchased will be usable by you in any 03-05 civic in which you choose to install it, or if you choose to break it down and use parts of it to rebuild other packs. You will have to either:

Have the PTC circuit open to satisfy the updated MCM
Spoof with a 30 Ohm resistor to satisfy the old MCM
Update the MCM and make sure the PTC circuit is open

PTC sticks and non-PTC sticks can be intermixed, and having a SINGLE non-PTC stick in the circuit means it's open, so you have to do... nothing to satisfy an updated MCM. You just loop in a 30 Ohm resistor if it's the old... or do the update.

The "junction board" traditionally refers to the end piece that houses the master switch, fuses, relays, etc. The change is not really in the junction board. The cut wire portion is under the junction board attached to what I'll call the "bus plate" that ties all the sticks together in series at that end. Of course, you can trace the wire externally and deal with it outside the pack - either cut it or put a resistor on it as needed - technically, you can do it at the connector.

ralphsworld1's picture

sounds good. a little confused but when i actually get into the build I will see what I have. This old battery I bought might need to be modified it being an original - because like I said all of these packs around town are all only a few years old. This one is 10 years old living in Colorado. People have done their 3rd or 4th battery by now. Great to learn and again thanks for the info.

ralphsworld1's picture

bulletin 10-083 talks about the software and compatibility but doesn't say why the newer battery is or is not compatible.

seekash215's picture

Hello everyone, I am new to this site/thread.

I'm thinking of purchasing a 2004 honda civic hybrid with 150k miles, 5 speed manual transmission. current owner says it may need a clutch/throwout bearing, he says it runs and drives, so it could be neither. it's listed for $1200. I spent a few years working at a car shop and learned a great deal, the clutch is a bit out of my ability, but my worries lie in the battery pack because of the age/miles on this car.

finally, my question: Would any of you consider buying it? Why or why not?! Thank you all very much for your time.


S K's picture

Only if you're okay with spending another $3-4K on it. It doesn't matter if the battery is bad now or not. It will be soon.

seekash215's picture

if the $3-4k is for the battery, i'll hopefully be able to refurbish it myself when it starts having problems. I have a daily driver, 98 Camry with 250k, but my commute to work is about 25 miles one way so I'm beginning to worry about having only one car with such a long commute. A hybrid definitely sounds enticing to me. Would you strongly recommend not buying it? due to mechanical issues with this particular car, difficulty of battery refurbishment, other problems, etc... I'm hearing mixed reviews as I'm checking around, some say they love their civic hybrid, other places say they have one of the worst battery failure rates on the market which makes this a bad car to buy. Not sure what to think

seekash215's picture

Also, in general, are highway miles or city miles better for the battery??

S K's picture

The process described on this page is not reliable long term and requires investment in a salvage yard pack or other source of sticks - which can be a total miss these days and are much harder to find. Reconditioning without replacing failed sticks is typically repeated every 3-6 months. If you want a "permanent" solution, pack replacement is the only option. Grid charging might get you by for a couple years.

The 03-05 had "okay" battery failure rates - way higher than the Prius, but not criminal. The 06-08 were about 1 in 6. The 09-11 were about 1 in 3. You would be better served by a small used 4 banger without a hybrid system attached. Used hybrids are almost always a worse choice than a used gas car if you're worried about money.

The less the battery gets cycled, the better. The less acceleration and deceleration events, the better. Thus, sustained speeds over flat terrain is optimal for long battery life. Stop and go driving, and hilly terrain are harder on the battery.

Michael Welch's picture
Friends, let's please keep this discussion to battery packs, specially reconditioning. To let it get too far off topic will make it more difficult for other readers to find the excellent pertinent info that is in the comments section. Thanks.
jaimenavarro2017's picture
S K's picture

Thanks. Okay. I believe you. I applaud your mechanic's creativity, yet I fear it. :)

jaimenavarro2017's picture

Its been getting me from A to B but its a pain in the butt, belt constantly gets loose and I have to make it home or nearest safe place with just 12v battery. What do you mean by fearing this? Do you think it may cause problems to the engine?

S K's picture

I fear the reliability... :) I don't see that it could cause any harm.

jaimenavarro2017's picture

Oo right i get your point. The vehicle has about 90k miles. In your opinion how much would be a good sales price as is?

S K's picture


jaimenavarro2017's picture

Wow! Im better off selling it for scraps. O well, its a learning experience.. I will definately think twice before getting myself into this hybrid vehicle mess.

S K's picture

$500-1000 is about scrap value. At this point, it's a problem, not a car. You're selling a problem. Your market for your product is TINY - either tinkerers, or people who don't mind spending a lot of money for very little car. Used hybrids out of warranty are either great or a land mine. There's very little in between. With the alternator removed, a fully functioning reliable car with a clean title, now you're talking blue book, especially if there's a warranty tied to the battery.

The fact that the car still runs and can get you from A to B (mostly) is misleading. You have had a major system failure. The HV battery is part of the propulsion/emission system. It has failed. It's as significant as a blown transmission. How much would you pay for a parked car with a blown transmission that you know is going to set you back at least another $2-3K? Not much.

jaimenavarro2017's picture

You are correct. I think i have researched and heard enough from professionals to make a decision. Appreciate all the help SK.

karlt's picture

I speak Spanish, sorry my English is not very good. I use the google tool to translate.

karlt's picture

One question, for what it is, the lining that each battery has. What happens that I send to buy Ebay, the batteries but these are badly armed since the sensor was in different position to the hex nut or block, which has to be screwed.

What I did was remove the lining and as in my country do not sell that liner I put tape to isolate. They could tell me if it is only a lining for protection or the aid to intense heat that they have to suffer.

S K's picture

Karl. What is your language? For 03-05 Honda Civic Hybrid. There are 3 white plastic sleeves over sticks at top of pack when installed in car. these are to keep those 3 sticks from being much cooler than the others. ALL sticks MUST BE COVERED with PVC shrink wrap (usually yellow or orange). DO NOT INSTALL STICKS WITHOUT WRAP. FIRE DANGER!

Michael Lamb's picture

Oh ya. One more thing I want to warn everyone about is the AC compressor on at least my '03. It likes to have pully bearing failures. I have replaced the AC compresor 6 times over the last two years for the same reason: the bearing honda put in the Ac pully is garbage and the grease dries out, heats the little bearing pins and locks up the bearing on the compressors aluminum housing snout. This either breaks off the aluminum snout or serpentine belt.

The fix is to replace the entire compressor. However, DO NOT buy any of the rebuilt compresors you find online. I went trough 5 of them and all failed within a year. I currently have a used compressor I bought from a junkyard, off of a car that had 95k miles on it. Crossing fingers a lot now.

There is also a shorter belt you could use to bypass the compressor if you dont need Ac anytime soon. Dont recall the belt number, but I will post the belt number here later. I recall Autozone stores selling a cheap one for about $10. Keep it in the trunk for an emergency.

Michael Lamb's picture

Hello again everyone.
Firstly let me say thanks to SK for taking the time to give really good advice here! Awesome.

Hi jaimenararro, I live near DC. What part of DC are you in? I sometimes drive that way for other business and so could possibly have a look at what you have going on with your HCH.

I just chatted with Haley at Bumblebee and she said they sometimes have used-refurbished packs available for less money than the usual total rebuilt ones for 2300 bucks.

Also it may be worth relating that I have seen a number of used IMA packs at the Pick-a-Part junkyards in Fredricksburg and Richmond for 140 to 300. If you have the time and patience you could buy a couple of the type your car needs and work the sticks over...Thinking about his idea further I think the Bumblebee option sounds better, as well as a lot less work for you.

I would advise against micky-mousing your car further with non-spec batteries. Could be dangerous.

It is also worth pointing out that at least my 2003 will drive ok-ish without the IMA pack working right. Very sluggish and it does use the 12volt battery for starting the IC engine a lot. But it will get you around town as long as you are very careful not to get into a bad driving/traffic situation.

Many years ago, I also modified my 12volt battery tray so it will accept a normal size car battery. Just measure how much space you can gain by cutting away all the little plastic dividers and stuff Honda put there and loosen/ cut the battery cable straps and hooks so the pos and neg ends have some slack and will reach the new terminals on the normal battery. Works great and allows you to start the car more often when the IMA is messing up too much.

jaimenavarro2017's picture

Hey Michael, i live in springfield virginia but constantly travel to my mothers in indian head maryland. Do you have an email? Also SK i have just taken pictures of engine but im not able to post on this blog for some reason ... now michael how would i be able to contact bumblebee to inquire about the cheaper refurbrished battery pack? Riding down south to several locations doesnt seem like a job im ready to take on I work even on my days off as im a debt collector and if i miss work i lose money. Finally the battery does help the car run sliuggish but battery life is about 1 hour and the first thing sign i get is that the steering wheel becomes really hard i thing its electric power steering. Any ideas how to make my battery last longer?

S K's picture

Post them on Google Drive, DropBox, Flickr, whatever and link them.

Rebuilds are on their "Products" page:

S K's picture

Just to reiterate, 80% failure rate across 12+ HCH2 packs. Out of the 132 dual-stick subpacks... that's less than 3 packs worth of subpacks, and only one TRULY good one. The other two packs need grid charging every 3-6 months. While BB does reconditioned packs, which I'm confident are among the best, they are still working with very poor raw materials. $2300 for 3+ years or about half that for 1yr. The choice is simple for me, plus new cells should definitely last longer than ones that are 10+ years old.

Dont' know about HCH1 compressors but the hybrid pulley/electric one on the HCH2 can go out. Ours failed and the dealer wanted $2K. I replaced it myself with a salvage yard unit for $120. I had to re-shim the clutch to get it in spec, but the total out of pocket including the magical compressor oil you have to buy and an A/C vacuum pump was under $400.

jaimenavarro2017's picture

Oh wow sounds great and not to mention the warranty sounds even better. Only problem, i was kind of looking to spend less then $1500. Would there be another alternative? Im in the DC area and as of right now my honda is running with the regular 12v battery and alternator. Problem is that idea that my regular mechanic happened to come up with decreases acceleration plus the AC is disabled. Also i have to constantly get belt tightened because lack of space made the installation of alternator very difficult. Any ideas? Ive even considered buying a couple deep cycle batteries to get the vehicle workig until my tax returns are in.

S K's picture

I'm surprised it's even possible to install an alternator on an '06 Civic. I can't imagine that was cheap. Actually, I would love to see pictures of it. I'm almost certain it's not possible as the 1.3L engine was purpose built for the HCH1/2 and was never in a non-hybrid vehicle. If I still had either of mine, I'd go look.

Unfortunately, what you are looking to spend isn't relevant. The ONLY solution to the HCH2 IMA battery failure is replacement if you're looking to not deal with it again for years. I have personally touched more than 12 packs with a 80% failure rate in reconditioning. They are junk. I know enough about what Bumblebee does when building new packs vs. what others builders DON'T do, to never spend my money with anybody but BB. There are others, and they are somewhat cheaper, but IMHO, you're just throwing the dice.

Sorry to sound so negative, but the batteries from 06-08 were horrible. The only worse ones were the 09-11. Failure rates were almost criminal.

jaimenavarro2017's picture

Ill post pics asap stay tuned. Does BB sell battery cell packs? As far as im aware and correct me if im wrong, I would need 22 individual cells or 11 pairs (06 honda civic)

S K's picture

BB sells full packs. You order, they ship, you install and you return ship your pack.

jaimenavarro2017's picture

Im completely, not tech savy so alot of these instructions sound like a foreign language to me. Does anyone know where i can get the battery packs already set and good to just install on my 2006 hybrid honda civic, with dead ima battery? Or would it be cheaper to just buy the whole thing?

S K's picture

I always recommend $2,295 with a 3 year warranty. If you're in the Phoenix area, I could help you.

Michael Lamb's picture

Hi karlt

It sure sounds to me like your IMA pack is near its end. Your choice as to how, or if, to fix it. Read over what others here have done and pick your path.

Since your fluid is recently changed I am guessing here that your trans may be up for a rebuilding. Not my field of knowledge though. How many miles on this car? If over 150k and the fluid was never changed before it may be time. Try to find a trans guy who is honest (long shot there) and who understands Honda CVT's. Some years ago I recall finding rebuilt CVT's online for about 1500 bucks with exchange (core) charge for old trans. Probably add on shipping too. Junkyard trans go for about 300- 500. Be sure you are dealing with a good yard though, lots of scammers in that line of business. Check the miles on a used one with your own eyes.

Your trans is smart enough to store codes on itself. Find a trans guy with the right kind of scanner.

karlt's picture

I tell him, every day. Do not go up 2 bars the battery. Uploads all but after 10 seconds the download and only stays with 1. then this last disappears and appears the battery of 12v.

I then turn off the vehicle, and start charging again, but still showing only 1 bar and CHRG bars, not full charge. The ASST.

In March last year perform the change of transmission fluid. But I was like 3 months without a vehicle because I was doing the recalibration. But I've been driving less than 10K miles.

A friend of mine has a scanner that allows to enter the functions of the hybrid, and in the functions of the IMA, I set it to leave high values and from there the load became very slow.

Do I have to change the transmission fluid?

Thank you for all your time.

Michael Lamb's picture

Hi karlt,
I know what is going on, since SK does not seem to know I thought I'd spend a little time on this blog today. BTW, SK you are doing a fine job here. Please continue. You are a real asset to everyone! I appreciate it.

karlt, What you are seeing is called a "major recalibration." The car computer does this when the IMA pack is getting really wonky. It is not very dangerous unless you need a lot of power in an emergency situation. At such times you are going to probably only have the 1.4 liter gas engine for power, which doesn't do very much for acceleration. Also your MPG will probably be suffering as well.

Also, it sounds like you have a CVT type of transmission. The "blinking D" means the trans is slipping too much and the computer is unhappy. Be sure you change the trans fluid in at least every 10k miles otherwise it is likely to slip a lot and eat itself to ruins. I see lots of these cars in junkyards with destroyed CVT trannys. It is not very hard to do yourself if you are mechanical in nature. Cost you about 70 bucks in fluid. A shop will charge you about 400.

BTW, I always thought it interesting that the 5 speed manual trans doesnt have anything like this maintenance problem. Mine is at 225k miles now and doing find. I get lots of recals now but I ignore them since I understand what the computer is up to. It is annoying, true, but replacing the IMA pack again is much more annoying for such an old car. I see IMA packs of the proper vintage in junkyards a lot these days. They cost between 150 and 300 bucks. But judging from what SK has related here it is probably not worth the effort for me to change all this again. Cells get worse with age, not better. So many of the packs in the 'yards are not going to be much better than what you currently own.

The line battery charger does helps. But I need to do it most every night to feel a real difference in performance.

Enjoy your car for as long as you can. I will sorely miss mine when it finally dies someday. Still at 50+ MPG!! Go team.

S K's picture

Welcome back Mike. HCH1 and HCH2 have 1.3L engines. Identifying it as you have, I can see how what he's describing could be a recalibration. I just couldn't make sense of it.

By "line charger," are you using what is more commonly referred to as a "grid charger"? Does your charger properly drive the IMA cooling fan while charging? If it does, you might be surprised what a pack-level reconditioning cycle can do provided you haven't actually had a cell failure. It essentially does what your article describes, but it takes less than a week.

karlt's picture

Hi, thanks for your answers.
I want to comment, I did the calibration just like you did. But I worked differently. I want to describe what happened.

The part where the green load bars are located at the time of going fast previously should be filled completely when braking. But in my case it only shows 4 bars. The charging battery goes up. But at the moment of accelerating it is downloaded very fast. In less than 1 minute it has been downloaded. And only leaves a bar or none.

Lately it is too much of a revolution, and then D begins to blink. I turn it off and it works normal.

Sometimes it does not show the battery charge bar.

It shows me the following errors.

Error code: 12 = MPI

Error code: 58 = load and discharge balance failure

FF, 27.4e 00

Thank you for your answers. please help me. I do not understand how the system works and I worry about the malfunction. I measured the battery with a tester and it tells me that it has 155V

S K's picture

I'm sorry. I'd like to help, but I can't make any sense of your post. Good luck.

chrislk1986's picture

Good to see this thread is still somewhat active. I'll spare the back story, just have a quick question I hope might be easily answered.

I have a HCHI with broken CVT belt, going to scrap car but take IMA batt out. Have HCHII that started throwing constant IMA light about a month ago, getting bad enough that 12V doesn't always charge. I know the HCHI-II have 144-158V respectively, but can the NiMH sticks be swapped? The IMA on the HCHI was on for the 3.5yrs we drove it but 12V never died. 12V on the HCHII has died 6+ times since August.

S K's picture

03-05 HCH1 sticks are only compatible with 03-05 HCH1 (and G1 insight, sorta)
06-08 HCH2 subpacks (welded dual sticks) are only compatible with 06-08 HCH2 subpacks
09-11 HCH2 subpacks (welded dual sticks) are only compatible with 09-11 HCH2 subpacks

chrislk1986's picture

Thanks, save me a lot of disappointment.

Looks like I might go for a Bumblebee pack and splurge for a 5yr warranty.

Do you use a Bumblebee battery or know of anyone who does? I'd like to get minimum 3yrs out of this 2007 HCH, and possibly sell it and get out of the Honda Hybrid game unless the Li HCH is a major reliability upgrade.

Thanks again.

S K's picture

I only install Bumblebee batteries in customer cars - 2X '07 HCH2. Performance was exceptional. I monitored Pack SOC and tap voltages as well as battery current on both test drives - the SoC barely budged, and they delivered 100A assist and 50A regen like I've never seen before.

I know the owner, and I have detailed knowledge of the process they go through to test and match the new incoming sticks from China. He builds packs based on matching down to the CELL level.

ADiaz's picture

Thank you for your post. i have been working with my 2007 civic battery for 2 months trying to figure out the conditioning process and what settings to use , i have a bought 6 pair sticks on ebay figuring that some would be bad. i first checked the the voltage on the new ones and it ranged from 7.9 to 7.4 volts per 6 cell. the ones from car were around 5volts thats when my car wouldnt start. I also changed the 12volt battery. . So now trying to recondition them using imax b6. my setting are now at charge 3.5 amp to 6400mah. 150 minute time auto. discharging at 0.7amp to 4.4volt limit . Last time using this setting 6 of 6 batterys charged to 6400mah with 8.5 volt reading. placed them back in car and ima light came on again. when charging some timed out and i restart and continue the charge for the remainder of the 6400mah.. I noticed when starting charge process the volt would jump to 8 volts within 100mah. on some . I would appreciate some feed back on settings and how to know whats good or bad.. Also how to check the mah in the battery.. cause i think the imax b6 will continue to discharge or over charge. before 6400mah is reached.

S K's picture

Please read all my posts in these comments. You are trying to diagnose a cancer patient from across a room using nothing more than the chart showing smiley/frowny faces rating pain from 1-10. You do not have the tools to do the job.

ADiaz's picture

Thank you.. there is so much information.. I gotta take lots of notes . you prefer the reaktor then the imax b6. and i should get the 360 power supply and cba battery analyser... . .

S K's picture

You're not going to fix your problem with a $15 Chinese knock-off Imax B6. You're still not likely to fix your problem with hundreds of dollars worth of high quality chargers.

Since my more active period of posting in these comments, I have processed 12 HCH2 (06-08) packs. Of those 12, only 3 were operable. One was a very strong pack that I expect little issue with for many months or even a couple years. One was workable with grid charging every 3-6 months. The last was marginal and needed grid charging about monthly.

Yep. That's over an 80% failure rate. The 06-08 battery packs were bad - way worse than the 03-05. The 09-11 battery packs were hellish with 3-4 year failure rates of 30% - yeah... 1 out of 3 packs failed within 3-4 years SINCE NEW. They were so bad, Honda extended the warranty on 09-11 Civic Hybrids to the CARB state warranty of 10yr/150K miles.

The only real and lasting solution is a new pack - either new from Honda (the same company that supplied all the failing packs) or an aftermarket. I have detailed knowledge of what Bumblebee Batteries does when building their packs with new sticks, and I vigorously recommend them.

Alternatively, get yourself 3-4 spare packs from salvage yards and you might be able to build a good one.

Good luck,


ChrisM's picture

My reconditioned battery is still going strong, and most likely because of it's unique circumstances. It was barely used, from barely being driven for 12 years. I have a 2004 HCH1 with 40,000 miles on it... Most insane, so knowing that the imbalance most likely came from lack of use doing this work made sense to try.

I synthesized S K's methods from various sources. Keep your NEW 12V battery out of the car while reconditioning the IMA battery, no sense in having it possibly parasitically drain from some random component in the car for a month while you do all this workto have the cars computer throw error codes when it doesn't like the 12V charge.

I did this in my fridge - freezer cold garage over night for a month in October... 3 days per stick with four iMax's at the same time after confirming three sticks were now good to go.
If you are in a warmer area of the world, use a box fan for extra cooling.

I did not use autocycle presets, I manually stared each step and made sure it finished before proceeding to the next one.

Give the battery sticks time to cool between charges and discharges.

1. Get a carbon pile battery tester from Harbor Freight or some other source. Good sticks will pass a load test of 90A for 10 seconds and stay above 5.4V.
I had one good stick out of 20 when I started.

2. Note with iMax B6 you can test internal resistance, I had readings anywhere from 30 - 120+ mOhm. I also checked between each of the following steps and logged the data in a spreadsheet. Since all my sticks came back to life, I don't know what readings would indicate a bad situation.

3. Hook up an iMax B6 or equivalent to one stick at a time. (legit models are $50 - $60 on Amazon), Set NiMH sensitivity to max (15mV was what I had, 20mV is good too), and discharge at 1A to 6.0V per stick. This can take a minute to an hour depending on the condition of the stick.

4. Set mAh limit to 9600mAh, no time limit, and Charge at 0.6A until done. Takes 12hrs - 16hrs.

5. Reset mAh limit to 6500mAh, no time limit, and Discharge at 1A to 0.2V. Also takes a long time.

6. Discharge again at 1A to 0.1V. Again takes a long time.

7. Charge at 5A (or 6.5A), no time limit until done, takes about an hour and a half.

8. Turn off mAh limit, no time limit, and Discharge again at 0.3A to 4.8V (4.7, 4.6) per stick.

9. Turn mAh limit on to 6500mAh, no time limit, and Charge at 5A (or 6.5A) until done.(Sometimes up to 9.5V and will settle lower, usually around 8.4 - 8.6V) Again, another hour and a half.

10. Let the sticks rest at least 1hr until cool, they should only be luke warm after charging at 5A to 6500mAh. Really hot will indicate a bad stick from what I gathered.

11. Load test with carbon pile tester at 20A, good sticks will stay between 6.4 - 8V. When you crank down the load V should go back up to around 8.2V. Wait a few seconds before second load test.

12. Load test at 90A, V should again stay above 5.4V, the lowest mine got were around 6.2V.

13. Put the battery back together and top the whole thing off with a grid charge overnight. I used the 0.5A @ 200V LED power supply suggest by S K. I left it charging for about 8hrs, final pack voltage around 167.5V, settled to like 162V.

14. Put NEW 12V in car, put IMA battery back in car. Make sure to seal the compartment back up so it's air tight, as that's what will help create the space for the cooling fan to work properly.

15. Car should start with no errors and no IMA light, unless you have other codes and issues.

ADiaz's picture

Thank you so much for the step by step. I need that alot. I will go to freight harbor and pick that carbon pile tester up... but since my car is a 2007 with HCH2 158.4 Volt 5.5Ah will the parameters be the same. like charging to 9600mah. or discharging to 0.2V seems really really low.. thank you

S K's picture


While your process can be applied to HCH2, the results will be atrocious. HCH2 cells are of notably worse quality than HCH1. They are also lower capacity at 5500mAh.

The only potentially cheap/effective solution is the grid charge/discharge option I link further down. In the vast majority of cases is at least as effective as what you did with individual sticks and can be done in far less time. The only thing it can't do is quantitatively identify bad subpacks; however, tap voltage monitoring during discharges can show outlier behavior.

To summarize - you grid charge the pack with the LED power supply providing adequate cooling (removed from car, forced air) for 20-24 hours. Exit air should never be more than 100°F. You're done at that point.

Bulb discharge with 2X 200W bulbs in series to 158V. Swap bulbs out with 25-40W appliance bulbs and continue discharge. Voltage will rise and then fall back through 158V. Discharge for about 5-7 hours AFTER it has passed through 158V.

Repeat the charge/discharge 3 times. You should note that the initial 200W discharge to take longer to get to 158V and the final voltage with the 25-40W bulbs will be progressively lower.

Grid charge for 6 hours, install and start car. Allow battery to be charged by car until it reads full. If charging stops before battery shows full, disconnect 12V for 30 seconds, reconnect and repeat in-car charging.

Remove pack from car again, supply cooling and grid charge for 8 hours. Install pack and go.

ADiaz's picture

Thank you SK for everything so quick to respond. Can you get me a link or type of grid charger u recommend. thank you

S K's picture

In my most recent message, I indicate I posted it further down, which tells me you haven't read this page or even my message, or you have read it, and you're too lazy to follow directions.

Please read this entire page. It won't take you that long. The 30 minutes or so it will take you to read this whole page may save your hours, days, weeks.

ChrisM's picture

Thanks Steve,

Right, I don't know if my methodology makes sense for the HCH2 pack... Grid charging/discharging is obviously faster. And if that doesn't fix the problem then you will need to get a new IMA battery, and as I understand it possibly a new battery control module computer... Very expensive.

Yes I read that the HCH2 battery pack is worse than the HCH1 as well. I am not sure how Honda made the same mistake twice and made the second gen worse than the first when they had to know the technology wasn't that great to begin with.

Anyhow, I wanted to make sure all my sticks were good before grid charging because I had started the stick work before vetting the grid charger thoroughly enough to realize I should have done grid charging in the first place.

ChrisM's picture

Thanks to this article and especially S K in the comments and on other forums out there, (terribly slow with ads),, and

I used the incredibly slow but effective iMax B6 charger setup and got an '04 IMA hybrid battery that was barely used to come back to life. It is working great now with an '03 computer and DC-DC converter.

After a couple weeks of troubleshooting I was left with error codes, 1570 and 1600. 1570 clearly means you have an unbalanced hybrid IMA battery.

Following S K's recommendations I load tested the sticks with a generic carbon pile load tester before and after. I had 2 ok sticks out of 20 in my pack before I did anything. After reconditioning all of the sticks are operating at the same level of performance. Yes, even with four running at the same time using the iMax B6 took a solid month. 3 days per stick using a synthesized methodology derived from the sources listed at the beginning.

S K's LED power supply "grid" charger is super easy to make and use. I will most likely be putting it in a proper box with IEC fuse socket for safety in the future.

S K's picture

Please post a follow-up as to how long your repair lasts.

ChrisM's picture

Will do sir. Thank you for sharing what you know about these packs with us.

karlt's picture

I have a question, I'm from Guatemala, have a civic hybrid 05 but I began to check the light of IMA.
I'm doing a repair test equipment batteries with AC Imax SKYRC v2. I want to know what kind of settings have to put it to the test and evaluate the burden of my batteries. You can help me. to give me instructions to place settings.

I currently have him Descharge Charge 0.6 A and 1A 4.8V configuration and stop charging to 6500mAh. I want expert help you can help

my email is:

Thank you

justevan's picture

SK or anyone
what is the best (and cheapest) way to set-up pack charge and discharge. I am a electronic tech. so I can build one. do u know of any proven ways to do so?

joncountry's picture

Does anyone know if this would work for a Toyota Prius ? Thanks.

YPATY's picture

Has anyone in the Washington, DC area tried this?

lmlisak's picture

Can someone give me the measurements of these cell sticks?

35mm x 385mm... along those lines

S K's picture

Aftermarket modules off Alibaba are:

34.0±0.5mm dia at their widest
382 ± 2mm length

I have used aftermarkets in packs, and they fit as well as the OEM, so I trust those numbers.

Curious. Why?

lmlisak's picture

I thought about buying a set of 20 from one of the Shenzhen companies... they have a 20 stick min order...
I have Chinese speaking managers where I work, so I can ask for their assist if their is a language problem.
Parameters from the vendor
Voltage: 7.2V.
Capactiy :10000mah( Original 6500mah)
Size: 35mm*384-394mm
Continue Discharge Rate: 100A
Support 50A charge rate
6 Cell per stack with both ends stainless square and hexagonal standard electric car battery nuts

So It sounds like you've done this route also...

S K's picture

No, I have not done this, BUT I have worked with one of the main battery builders for Insights/HCH1. He uses 8Ah sticks from China, and I have recently measured some for re-shrink wrapping used ones from 2012.

I would vigorously discourage you from the 10Ah version. It's an inflated/gimmicky rating. The technology doesn't exist to make the cells with that capacity in this application. The 8Ah rating is also a little gimmicky as it's not truly a capacity increase for the car, but it's a decrease in internal resistance that enables more capacity at currents well below the car's requirement. I have personally tested the 8Ah sticks at 20A discharges, and they test around 6000mAh, which is a little better than Honda.

Additionally, to give you a reference, MOST of the 20 sticks in the Insight pack from the battery builder are showing issues that will inhibit long-term trouble-free function, but will likely function well with periodic grid charging and discharging. These sticks were subjected to worst-case Arizona heat and extended periods of sitting

The effort associated with rebuilding a pack is very high. It will require minor modification if your pack still uses the PTC strips as new sticks typically don't include them and newer models don't use them.

If your IMA system has recently failed, and you still have partial function, grid charging and discharging could enable another 1-2 years of good function.

If you're still going the China route, avoid anything that looks anything like "KingKong" batteries. Their quality is very spotty. Additionally, don't expect any warranty to be honored.



lmlisak's picture

Hi Steve:
My check engine and IMA just started showing up a few days ago. I was a Bench tech for a decade, and I still dabble in my skills. so I believe I will not have a problem with the my 2007 I may be surprised when I open it up..if you say KingKong is one to avoid, I will need to be carefull buying from across the pond.
I cannot afford the retail and my thought was to just find the cell packs....
this Ali-thing doesn't support that many vendors in this type of battery... ( sigh )

S K's picture

First, get the code read. It's usually the battery, but it can be other things.

Second, check out your 12V battery (make sure you have your radio/navi codes before disconnecting). A weak 12V can trigger a marginal IMA issue. Have your 12V battery LOAD tested. If it tests at less than 80% capacity, replace it. The act of disconnecting the 12V will reset the BCM and IMA light. This will trigger a forced regen. Allow the car to idle and charge until the SoC gauge reads full. If it terminates charge before full SoC, do it again. Repeat the 12V disconnect and IMA charge to full SoC a total of 3 times (the last one usually takes under a minute). This process can often get an IMA light to go out for months. It doesn't fix it, it just improves the issue a bit and puts the light off for a while.

There are no viable Chinese replacements for 2006-2011 due to the fact they the Honda sticks are welded in pairs. Hybrid ReVolt and Bumblebee Batteries have fabricated replacement pairs from Chinese single sticks in their replacement packs, they are notably cheaper than Honda, and they come with a 3 year warranty on which you can count.

Again, I encourage you to to pursue grid charging. The HCH2 responds pretty well to them. I have 2X '06. You can build your own grid charger/discharger for about $90. Since the HCH2 fan is PWN controlled, you either need to devise a way to run it or charge/discharge with the pack out of the car. It can be done in a weekend, and you'll likely get another 1-2 years of life during which you can save for a new pack.


S K's picture

All, I vigorously encourage you to abandon stick work. It's generally a waste of time.

Chas, Per my comments below, the Turnigy Reaktor 300W. Cells should never be too hot to comfortably touch. 100-120°F is the realistic maximum. Get them hot enough, and you damage them.

Justevan, congrats on your results. Your success or failure will be determined in how long it takes before you start to recalibrate again. If it's more than 2-3 months, great. Don't expect it though. Insight G1 and HCH1 sticks almost never rejuvinate for a significant period of time due to increased IR and self-discharge of 1-2 cells in a stick.

All, I encourage you to pursue grid charging/discharging before you ever consider doing stick work. Here's a DIY BOM for a charger and a discharger:

This must be done outside the car; remove the pack and take it in the house.

The reward vs. effort of the above process is 100 times higher. You'll have about 1.5 hours total time invested, and you'll know 100% if your pack will refurb at the end, and it gives as good or better results than stick work in a single weekend with nothing more than occasional monitoring.

So, Chas, grid charge/discharge/charge the spare pack and balance them all in one shot in one weekend, eliminate 99% of the voltage depression and recover 20-25% capacity. Here's my before/after sheet:

Lastly, here's all you need to know about grid charging/discharging:

The only time you should do stick work is AFTER a pack has started to misbehave following a grid charge/discharge/charge. You can then discharge your as-removed sticks a single time and know exactly which ones are shite.


justevan's picture

Chas Seligman,
make sure after charging and discharging as S K stated below.
then do another charge, make sure it reaches at least 9.4 to 9.5V.
if not try deep charging to 4.2, just remember when discharging past 6V that u do it at 0.3A. also make sure the hybrid battery fan turns on when the battery charges. as when u slow down and stop, the fan should still run for a little. my fan was located in the trunk behind the black felt paneling

Chas Seligman's picture

Which Turnigy did you use? The Imax just doesn't seem to get it. When I nwent a couple of the sticks never got hot enough to 'not touch' just pretty warm. Did you replace yours from the spare battery pack. I've purchased a spare and went trough it again with the Imax and didn't really find any bad ones. I purchased another total balancer online and it seem to work the first couple of times but lately the IMA came back on and the 'charger system' doesn't act right.
I have two of these cars that I love (getting in excess of 40 mph on both) so I have a vested interest in figuring out how to fix this problem.
Since I have a spare battery pack I want to start on that one and get it all re-balanced or identify the bad sticks.
Thanks for all your imput!

justevan's picture

i just completed this task. it was successful! i have a Honda Civic Hybrid '04. i bought a used battery pack conditioned each rod (20). 4 were suspect. i removed my own and recond. 4. installed and passed emmisions. i used the IMAX B6 charger and the Turnigy (it is faster).
follow discharge and recharge instructions below. some sticks will be
very hot , to hot to touch. these are bad, maybe more conditioning may be required. USE FANS!!. i used a 10A 12V powersupply for both my rechargers, this will get hot too. good sticks will charge upto 9.5 to 9.6V and start to get warm around 9.3V(aprox.), but not super hot.
i also used 12AWG copper wire with screw on each end so not to damage the treads of battery with a clip

S K's picture

How long did it last?

gpa2042's picture

Justevan, did you run your imax in auto recycle mode? I tried to run for 3 cycle automatically but every time when it charges 6500mAh it stops and do not start to discharge automatically and i have to start it again for discharging . I do believe the batteries are rated 6500 mAh for 05 civic hybrid but my charger just keeps charging and stops exactly at my capacity cut off set of 6500mAh. Am I missing something that is not allowing it to recycle automatically?

currentchallenged's picture

Does anyone have definitive information what to set the IMAX B6 units for to process the reconditioning? I had bought a junkyard unit and it failed after 6 months. Now I just want to try to recondition the sticks to see how many I can come up with that are good. I have seen lots of posts and pages, yet cannot find anything posted as to what actually is used.

justevan's picture

follow the comments. when u start the charging process. go to setting. then NiMh sensitivity and change it to 20 (defalt is 4).
only for the .6A charge step (will take 16 hrs), after that change setting back to default. then 1st discharge is at 1.3A. then its full
charge and discharge to 6V. below 6v u must discharge at .3A (5.4, 4.8, 4.2)/ charging and discharging inbetween .
i did this , took a month , but it does work.

justevan's picture

follow the comments. when u start the charging process. go to setting. then NiMh sensitivity and change it to 20 (defalt is 4).
only for the .6A charge step (will take 16 hrs), after that change setting back to default. then 1st discharge is at 1.3A. then its full
charge and discharge to 6V. below 6v u must discharge at .3A (5.4, 4.8, 4.2)/ charging and discharging inbetween .
i did this , took a month , but it does work.

S K's picture

Did you read any of the comments? The IMAX is completely worthless for refurbishment. It can only drain 5W of power from a stick, and it takes a week to do a pack. The car subjects these sticks to 100A. 0.8A isn't going to give you any diagnostic value whatsoever.

I recommended the Turnigy Reaktor 300W charger. It can charge 6X faster than the Imax B6 and it can discharge 4X faster natively, or it can discharge 75 times faster in regenerative mode.

What I really recommend now is that you investigate grid charging and deep pack discharging. You can do it in a weekend, and your pack will likely improve significantly. Results in the Insight community have been great.

Check out:

You are pursuing efforts that have been demonstrated to be very ineffective and represent a very large time investment with very low payoff.

EDIT: To answer your question... If you insist on pursuing...

Disable all timers and capacity safeties.
1) 1A discharge to 6.0V (1.0 V/cell)
2) 0.6A charge for 16 hours (you'll have to monitor it and restart it if it stops). You can stop before 16 hours if all six cells are comfortably warm to the touch (about 100°F).
3) 1A discharge to 0.2V
4) 0.5A discharge to 0.1V
5) 5A charge to termination. Cells should be warm or very warm but not uncomfortably so, and they should all be about the same temp (< 120°F)

The above process deep discharges the stick to wipe out any voltage depression and will restore 20-25% capacity for a given discharge. Yes, you will reverse cells. No, there is no way to damage these very robust cells from reversal at these low currents.

What you can't fix is Internal resistance and excessive self-discharge. You likely have many sticks that exhibit this condition.

The BEST way to truly diagnose bad sticks is to:

1) grid charge pack for 24 hours
2) deep discharge to < 1V using 2X 100W lightbulbs in series (yes, the whole pack down to <1V)
3) grid charge 24 hours
4) Install and run until recalibrations become excessive or you get an IMA light.
5) disconnect 12V battery, reconnect 12V battery (clears the State of Charge from the BCM)
6) start and rev car to 3500 rpm to force charge battery until battery shows full.
7) remove and discharge sticks to 6V at 10-20A loads.

Good sticks will give you >3000mAh.
Okay sticks will give you >2000mAh.
Crap sticks will almost never reach 1000mAh

Good luck,


B Styles's picture


Thanks for all the info!

I just purchased the Reaktor. What is a good power supply for this charger? The iMax chargers I currently have are the dual power AC plugs. I was using the wall plug as my power source for them but I won't be able to do that with the Reaktor.

Also, what would the best settings be to use for reconditioning the the sticks with the Reaktor charger?

Once again thanks for all your help and advice. Hopefully I will be able to recondition a decent battery pack for my HCH.


S K's picture

EDIT: I just received my Reaktors... they are NICE. Finish and interface is MUCH better than any of the Chinese knock-offs I referenced.

EDIT #2: While the 20W discharge rate isn't fantastic, it's pretty good. I've gotten accustomed to 10A and 15A discharge rates with other pricier devices. The Reaktor also has an internal resistance measurement feature, and it comes with temp probes, which I highly recommend using.

This should drive one more than sufficiently. I have 3 of these running my farm of IMAX B6, the reaktors and a iCharger 206B knock-off:

360W. I've run them at 300W for extended periods with no issues.


1 cycle at:
mAh limit, 9600 max
no time limit
Set NiMH sensitivity to 20mV, so it doesn't shut off prematurely
60 minute rest period
0.6A charge rate (will run until it reaches the 9600mAh cut off @ 16 hours)
1.3A discharge rate to 6V

For subsequent cycles:

Reset NiMH sensitivity to default
6.5A charge rate
Max discharge to 6V
Manually discharge at 0.3A to X

X shall be 5.4V, 4.8V and 4.2V for the 3 cycles. When going below 6V, do this MANUALLY at no more than 0.3A. You're driving cells down below voltage depression thresholds and causing reversals at LOW current for relatively short periods. This will not harm these robust cells. Deep discharge and reversals under low current have demonstrated substantial capacity gains.

4th time:
6.5A charge rate
Max discharge rate to 6V/stick
That will be your final capacity.

After these efforts are complete, I highly recommend you build your own grid charger for less than $75 or so.

Good luck!

S K's picture

My guess is you purchased the non-genuine SKYRC IMAX B6 for $25 each or a bit more for the AC models. I have several of these, and I have exactly the problem you describe. Some do it most of the time, some do it almost never. This problem is all too common with the Chinese knock-offs. These sellers get the same stuff from the same manufacturers. I fully believe there is a defect with these chargers.

You may get more success by pumping it up to 5.0A charge.

Lastly, the chances of you refurbing the sticks from a 2004 are very poor. At 10 years, you're looking at 10-20% deterioration from age alone. I am in the process of analyzing a pack from a 2003 (mileage unknown), and the bulk of the 6.5Ah rated sticks are coming in at 4.6-4.8A AFTER cycling.

I'd return all 4 of those chargers for a refund and place an order for a couple of these:

They have a 20W discharge capability compared to the 5W of the B6, so they can literally discharge as fast as 4 B6. If you rig 2 sticks in series, you could use the regenerative discharge to test two at a time at 20A discharge. I just purchased 2 of these, and can't wait to get them tomorrow.

Good luck,


B Styles's picture

Hello Micheal Lamb,

First I would like to tell you that your write up is excellent and I was able to remove and dismantle my hybrid battery with minimal difficulty.

However, now I'm having troubles and I figured this forum would be the best place to ask for help/advice.

I have a 2004 HCH. The IMA light has been on for a few months now and my gas mileage has went from 42 to 30 MPG, so it was time to get a new hybrid battery. After doing some research online I came across a few ways to recondition the battery myself. Using this site and your experiences as my guide, I started the steps to recondition the battery.

Since I knew I was probably going to need another hybrid battery, I bought another one off eBay for about $350, along with 6 iMax B6 chargers. I decided to take apart the spare battery and test the sticks inside first.

Now this is where I am my troubles. On the initial charge a lot of the sticks were not taking full charges that made sense. The iMax would read the charge was full in about 20 minutes and I would get reads of 29 - 410mAh.

These are my settings:

Timer - Off
mAh Limit- Set to 9600mAh
Charge - 0.6A

The weird thing was there were times when I could have 3 or 4 chargers going off at the same time with the same "full charge" reads with low mAhs (30-250mAhs). I thought maybe I had some bad iMax chargers but I bought them from 3 different sellers so I don't think that is the case. I also thought all the sticks in the spare battery were just bad but I don't think this is the case either.

I just want to know if you came across this problem when you were charging your sticks and if so what did you do to fix this?

Also, if anyone else in this forum has come across this issue please feel free to give you advice/fix. I just want to do this right the next time when I try to recondition the hybrid battery that was in my car.


S K's picture

I have done this on 4 HCH2 (2006, 2007) packs. The IMAX B6 is a poor choice as its discharge current is limited to 1.0A up to 5Watts. Testing stick pairs is not a good idea as the B6 will be limited to about 400ma discharge current and may take the better part of 15-16 hours. Single sticks are limited to 800mA, and considering that these cells are rated for 100A loads, 800mA isn't a good representation of performance in the car, but it's better than nothing.

A critical factor in stick cycling is ensuring the cells are balanced within the stick from the start. This is best accomplished with a 600mA 16 hour timed charge (controlled by setting mAh limit to 9600) for your first cycle (okay to charge pairs like this as it's faster). Discharge sticks to 0.9V/cell and then repeat twice more with 5A charge and 1A discharge cycles to 0.9V/cell. Repeat a 4th time to 1.0V/cell and consider this your final capacity from which to determine replacement or reuse.

Limiting your current isn't a good idea as charging efficiency isn't 100%. HCH2 sticks are rated at 5.5Ah or 6.0Ah depending on source. I use 6.0Ah, and when I charge with delta V cut-off criteria at 5A, the IMAX reads about 7700mAh pumped in.

This is a laborious process. I recommend the purchase of multiple non-genuine IMAX B6 from eBay (about $22 each). I have 15 of them. It's nice to be able to sort through a bunch of sticks in just a few days.

I also use a CBA III battery analyzer (CBA IV is currently in production) to discharge test the sticks at 14.5A to get a more accurate reading of their capacity at higher loads. Discharge takes only about 25 minutes, so I can do a whole pack in a day.

P.S. Regardless, nice write up of your experience.

Michael Lamb's picture

Hi Irfan ul Haq,
The answers to your good questions are as follows:
DIsable any timer limits on your iMax.
Charging the sticks first then begin cycling is a good idea.
The iMax has a 5 cycle limit, but you should get a good idea how each stick set is doing after about 3 cycles. If they are doing ok continue with 5 cycles.
The cycling Amps should be as high as the iMax will allow. I think this is 5 amps.
Doing all 12 cells at one time should not be a problem. It will just take longer than my 6 cells per stick did.
One more tip: set the charging limit at 6400 mAH. I think this is correct for you 2006 HCH. Mine was 6400 anyway. I suggest you do some additional research on that issue yourself. Set the charging limit accordingly.
Best wishes

iuhaq's picture

Dear Mr. Michael Lamb, Good Day!

After reading your article, I thought of giving it a try with my Honda Civic Hybrid 2006. I bought a battery pack from junkyard so as to keep the car running while reconditioning my battery pack.

I now have a HCH Battery pack, and have dismantled. It has 22 sticks welded together in pairs making 11 pairs. Looking at the welds, I will not be able to remove sticks from pairs therefore I thought to get the performance data of the stick pairs and remove the bad pair sticks and replace them with good one (as I have two battery packs available).

For reconditioning, i bought a new charger/discharger i.e. iMax B6 AC (Dual Power) 80W, which can charge NiMH up to 15 cells, as written on its box.

I tried charging one pair of sticks, but the charger stopped at 140 mins, and when i checked the settings, I came to know that there was a time limit defined for the charging as 140 mins, which I disabled.

The instructions which came with the charge are difficult for me to understand, therefore I am writing to you to take help to setup my charger for reconditioning the stick pairs.

My questions are as below:

1. DO I need to charge stick pairs before starting discharge/charge cycle? If yes, then what will be the settings of my charger? Current, time limit (if any) etc.
2. How many discharge/Charge cycles do i need to do to get performance of sticks so as to decipher between good and bad stick pairs.
3. What will be the settings of discharge/charge cycles i.e. Current for Discharging, current for charging, time limit to be removed?, and other settings on my charger to successfully get performance data.

Each stick has 6 cells, and a stick pair means 12 cells and as per charger specifications it can charge up to 15 NiMH cells. Therefore, I would like to do the process on stick pairs rather than individual sticks, does this make sense?

Kindly reply to me on above so i can start the reconditioning of my HCH 2006 IMA Battery Pack.

Kind Regards,

Irfan ul Haq

kilog's picture

All my congratulations for this comprehensive and wonderfull job.
Can I do the same for the RX400H lexus of my brother?
The HV Batt are down
and from here (Douala - Cameroon) in Africa there is no other solution than trying to refurbish the HV batt and start the car.

Michael Lamb's picture

Judging from what you wrote, I would have to guess that the HCH and Insight packs are similarly controlled and will likely act the same disconnected. However I would not advise doing so myself. Be careful, best of luck.

repurposedartifact's picture

It is only being driven on rural roads during daylight hours. I was concerned that there may be some sort of additional electrical problem with having the cells removed as opposed to just having the battery breaker flipped off. We have been driving our 1st gen Insight with the battery breaker off and it is totally fine performance wise for our normal use. It is important to my wife that both cars are drivable.

Michael Lamb's picture

Possibly, but like I said I never tried to do that. The closest thing I have experienced that might be like having the pack out, is me driving when my Honda HCH does a "recalibration" on its own. If I am tring to accelerate during one of those, the car is a real dog and has a hard time getting out of it's own way. During hot weather (and when the air conditioning is on) this sluggishness gets pretty hairy in traffic. If you really must operate the car in such a state, be very very careful. None of this is worth risking your life over you know.

Michael Lamb's picture

I have never tried to operate the car without the pack installed. Off hand though I would not advise doing that since it could make the car unsafe in traffic.

repurposedartifact's picture

Thanks for responding Michael. I don't know how you mean that the Insight would be unsafe with the battery sticks removed from the pack. Would this be any different than running the car with the battery cut off switch turned off when batteries are in place?

repurposedartifact's picture

Is it possible to put the battery pack back in the Insight without the battery sticks? I'd like to drive the car on just the IC engine while the batteries are conditioning over the two week period.

Michael Lamb's picture

Hi mortonarts,
The Imax comes with directions on making multiple cycles. Please be sure to read the instructions carefully. Also read the rest of the comments here for more useful tips.

mortonarts's picture

Hey all. So I bought 20 sticks of stripped batteries(No heat shrink) and I bought 2 iMax B6 chargers online. For some reason the battery tender will not do more then one cycle through. I have to switch it from discharge to charge to charge to discharge. Does anyone have better directions on how to use these chargers? Also they came in the mail with no power chargers. I used a few laptop power converters I had laying around. Any help would be great as I cant afford 3 grand on a new battery.

S K's picture

Under no circumstances should you install sticks without heat shrink into packs. This has been known to cause fires in Honda Insight battery packs. The mounting rubber is conductive enough to heat up and burn.

Chas Seligman's picture

Let's be honest about the instructions included with the iMax...they suck. I read them and reread them and couldn't make heads or tails out of them, so I just played with the buttons to get an understanding on how to work the darn thing. The best thing about the iMax is it's smart and won't let you do anything too stupid or ruin the batteries.
If I remember correctly in order to change the number of cycles the system had to be in the C/D mode with number of cycles flashing. While that number is flashing press the green button and that should increase the number of cycle the charger will cycle through.
I agree with the author that you don't need any more than three cycles because the batteries do not improve any more than during the third cycle. I tried five cycles and the difference between a five cycle charge and three cycle charge is very minimum

Michael Lamb's picture

Hi Chas
The best values for D and C are "the more the merrier." All the chargers you will find have a max D and C setting. Choose the highest one. This is far lower than the car computer will have zipping though the cells when the car is in operation so do not overly worry about the cell overheating during reconditioning. The charger will automatically keep things in a safe range. I believe many chargers also have an external temp probe you can buy just to be certain, but I did not find this expense necessary. Also if the cells get a bit too hot they are gonners anyway. A good cell will never get much over room temp if it is working correctly under load.

Michael Lamb's picture

Hi everyone! I am the author of this article and will try to answer the concerns I read here. First off though let me ask you to re-read the entire article until you recall most of it when you have a conversation with someone. Most of the questions I have seen all relate to things ALREADY outlined the the article. I really hate repeating myself so please do me that little favor. Thanks.

A couple questions I have been asked that have not been touched on are:

1) Can I use some other type of battery pack (i.e., LiPo, homemade NiMh etc) The short answer is NO!! Not just NO but "you are crazy if you do" type of NO. The reason is: Honda makes the pack in such a way that the computer actually communicates with it and if the computer doesn't like the conversation nothing works right.

2) Can I use more than one charger to speed the reconditioning up? Yes you can. Use any of the charger made for reconditioning NiMh cells, you do not necessarily have to use an IMax. I used an IMax because it came with the car when I bought it.

3) Where can I buy used sticks? The best I can say is that they are getting rare to find and the ones I have heard other people finding online and at junkyards are not a lot better than what they already own. I suggest that if you cannot find good sticks then make the best of the ones you do have by carefully reconditioning them. Do not rush the process. Chemistry is at work in the cells and believe me it doesn't like being rushed.

Chas Seligman's picture

This was a very useful article and I used it to recondition my 2004 Honda Hybrd also with the iMax that cost around $65. It took about 3 weeks to recondition all the stick and a couple of them I reconditioned to make sure they were within 10%. One question I never really figured out was what were the optimum values of the charge value (volts and amps) s well as the discharge values of the same. As another person asked and I also have searched out these numbers and could not find any information on this subject. Any insight on the optimum values would be a great help because I do not think this will be the last time I go through this process. Thanks for your time.

currentchallenged's picture

One question I keep seeing, but never seeing the answer for (and I have been searching a number of threads and sites.

When using the B6, what are the values used. From charging to discharging, voltage and configuration? I know very little about electricity and am probably not the best person to be trying this, but I am good at following directions, as long as they are in layman's terms.

I went and purchased 4 of the Imax B6 (clones most likely) and a junkyard HCH battery. I have had issues with the charging and such of my 2003 HCH but never got anywhere with it. I average 40 MPG and until I can find a replacement hybrid, I have to get this one to pass emissions.

So at the moment, I have 2 batteries, one in the car, one on a bench. I just need to start the recondition process and could use some hand holding while getting it started.

Computers I can understand, Anything that Nikola Tesla could have thought up, not so much.

S K's picture

Disable timer
set mAh limit to 9600
charge manually at 0.6A until it shuts off (about 16 hours)
discharge to 0.9V/cell at 1A (it will never read 1A, will peak at 0.8 or 0.9)

Set c/d cycles to 2
set charge rate at 5.0A
set discharge limit to 0.9V/cell
set discharge to 1A
run 2 cycles

Conduct single charge discharge per above except to 1V/cell. This is your final capacity.

Wolf Baginski's picture

This process is lengthy enough that you have to wonder if a vehicle like this is designed for a long life. Most of the total energy cost is still the manufacturing. And, from my own experience, a Honda Civic may reaching its mechanical limits after two battery packs. I'd certainly want to look closely at the rest of the vehicle, to judge how much time I could get out of it.

There are alternatives to Honda battery packs, still expensive, and this process is trading time for cash. I would consider buying more than one battery reconditioner. Spending another $55 to halve the time, if your domestic wiring is good enough, is almost a no-brainer.

I understand current models use Lithium-Ion cells. You may count me as nervous about the propects of that. Not just the reputation they have for fires, but a general feeling we don't have enough experience of the technology to feel comfortable. These machines could warp the whole used-auto market, you can see a $3000 bill on the horizon. The price ought to be lower, but will it be?

I think we are all still learning.

Michael Welch's picture

Some further info from the Author Michael Lamb:

During my HCH rebuilding ordeal I tried many different settings but found that the following worked out ok:
Set the Charging and Discharging settings to as high as the Imax will allow.
Disable the timer setting.
It is your choice to disable the alarm. I had mine "on." It would often wake me up at odd hours of the night, but I was in a hurry to get the work done so I put up with it.
The other settings the Imax has can be left on the factory defaults. They worked well enough in my opinion.
Make certain your Imax is set on "NiMh."

Yet More from the author:
A junkyard is about the only place I would find a used IMA pack. Mine cost me about $300 (noted in the article.) However I have been seeing them get a lot more expensive since there are fewer of them available as time goes on.

I sometimes see them on Ebay too, but I have heard some seriously negative things about Ebay sellers selling really messed up sticks as "working." Good luck getting your money back.

I wish you the best of luck locating used sticks (or packs) that are still worth spending money on. As these cars get older, so do the cells/sticks that are in them. Batteries do not get better with age either.

It may also be worth noting that I ended up "buying" a "cheap" Honda factory refurbished IMA pack from the Honda dealer where the car was originally purchased. This was some 20 months after the article came out. Check with whoever originally sold that car new for any deals they may be offering.

Also there is a Class Action lawsuit settlement going on right now. Look at for more details on this.

There are also a number of small claims actions around the country if you care to take your chances in a courtroom for yourself. Check out
Her case may give you some pointers on how you can proceed if you care to do as she did.

The author on a related subject:
I also sometimes like to caution owners of Honda hybrids which have a CVT transmission (which is most HCH's) to change the tranny fluid every 12,000 miles (or with each engine oil change) to avoid early transmission failure. Following Honda's service advice on the trans WILL cause the owner problems much sooner then necessary. I find lots of dead HCH transmissions in the junkyards I frequent around here. BIG money replacing a CVT! Costs more than the entire used car does currently. Search online to find some graphics that show how to change the fluid yourself (saves about $400 labor by DIY).

akvenkatesh's picture

Hello Michael L,
Can you please explain the charging amp/volt used .
When you say that the batt was discharged, was imax-b6 used to do this job.

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