Top Ten Battery Blunders and How to Avoid Them: Page 4 of 4

Intermediate

Inside this Article

Big battery, big mess. Don’t try this at home.
Big battery, big mess. Don’t try this at home.
These batteries have definitely seen better days.
These batteries have definitely seen better days.
Wrong Battery Type
Starting batteries work great in your car, but will quickly fail if used in deep-cycle applications.
Improper Size
A large battery bank requires a large charging source.
Improper Watering
An extreme result of battery neglect.
Many Small Batteries in Parallel Strings
Use bus bars to parallel multiple series strings.
Failure to Prevent Corrosion
Notice the parallel connections on the left side of the photo—the worst corrosion is at these stacked cable lugs. Batteries with corroded terminals will receive less charge, and will fail early.
Lack of a Protective Environment
A beautifully installed 48 V battery bank—sixteen 6 V batteries connected in two strings of eight. These big Surrette batteries have two holes on each terminal, so cable lugs don’t have to be stacked. The peaked battery enclosure allows for excellent hydrogen venting.
Lack of Proper Charge Control
Proper controller settings are critical for battery longevity.
Modern battery monitor
Example of modern battery monitor (amp-hour meter).
Modern battery monitor
Another example of modern battery monitor (amp-hour meter).
Big battery, big mess. Don’t try this at home.
These batteries have definitely seen better days.
Wrong Battery Type
Improper Size
Improper Watering
Many Small Batteries in Parallel Strings
Failure to Prevent Corrosion
Lack of a Protective Environment
Lack of Proper Charge Control
Modern battery monitor
Modern battery monitor

BLUNDER #9 Improper Charging

The surest way to ruin batteries within a year or two is to keep them at a low state of charge (SOC) for weeks at a time. Active battery material will crystallize, covering the plates, which will become permanently inert. We call this “sulfation.” Ideally, batteries should receive a 100 percent full charge about once a week for good longevity, and more frequently is better. If this takes a full day of backup charging with a generator, do it! Use your monitoring system to know when full SOC is reached. If you don’t have an amp-hour meter, watch for the voltage to reach maximum and the charge current to drop to a low level. This means the batteries are unable to accept much more energy, and are accepting only a “finish” charge.

In winter, some people run their backup generator for an hour a day—just enough to prevent the system from shutting down. Bad idea! It may be better to run it for ten hours, once a week, or whatever it takes to fully charge the batteries, instead of partially charging them more frequently.

Finish-charging a battery bank with an engine generator is an inefficient use of fuel, and results in extremely long generator run times. As a result, generators are typically shut down once the absorption charging stage is finished. But at this point in the charging process, the battery bank will only be at about 85 percent SOC. Since regular, full battery charging is important for battery longevity, make sure that your RE sources are topping off the battery bank after the generator has done the bulk of the charging. Relying on your PV system to provide the finish charge may be difficult during winter months. Another option is to set the inverter–charger to equalizing mode (see below) during generator charging about once a month to ensure that the battery bank is getting fully recharged.

The extreme of undercharging is called “overdischarging.” Voltage should never, and I mean never, be drawn below about 11 V (for a 12 V system), or 22 V (24 V system), etc. System controls and inverters usually include a “low voltage disconnect” (LVD) function. If you have DC loads connected directly to the batteries without LVD, you are asking for trouble. It’s better to lose power than to squeeze out another watt-hour and damage your batteries. Metering is vital here, because if you wait for the inverter to shut down or the lights to go dim, it’s already too late—batteries will likely have lost a portion of their capacity and life expectancy.

Finally, flooded batteries need to be equalized at least four times a year. Exactly how often depends on several factors, including the size of the battery bank in relation to your charging sources and the average depth of discharge during cycling. During normal battery discharging/charging, the individual cells of each battery will stray from a common and consistent cell voltage. Equalization can be thought of as a controlled overcharge of the battery bank that serves to both equalize cell voltage, and provide an aggressive and necessary mixing of the battery electrolyte. Equalization charging can be done with your PV system if your array is large enough, or with an engine generator or the grid. Most PV charge controllers and inverter­­­­–­chargers have battery equalization functions.

BLUNDER #10 Exceeding Your Energy Budget

If you remove more energy from your battery bank than you put in, your batteries will suffer. It’s not the batteries’ fault, yet this is the most frequent cause of complaints about batteries “not holding a charge.”

Here is one common scenario: A well-meaning appliance seller or mechanical contractor sells you a device that uses “very little electricity.” Ha! They don’t know about the initial expense of solar electricity. For example, about US$3 will buy you about 40 KWH per month of grid electricity. But adding more PV and battery storage to meet this load could mean an investment of several thousand dollars! Or, without upgrading your system, this would require frequent generator backup (especially in winter). The same blunder also happens when a resident decides it’s trivial to leave a coffee maker or large TV on all day. Even low power loads will add up if they’re running 24/7. When people don’t accept this reality, they overdraw their energy account, and often blame the batteries.

Love Your Batteries!

If I had more pages, and I could show the Top 40 blunders, from transportation nightmares to eye injuries to divorce. The lesson: Accept professional advice and service.

Lead-acid batteries are an old but durable technology. They are about 80 percent efficient at releasing stored energy—few high-tech storage systems come close to that efficiency—and they rarely fail suddenly. With good management, you’ll know when to replace them before they let you down. And even then, they are fully recyclable. Give your batteries what they need, and your batteries will do the same for you.

Access

Windy Dankoff 

Other Resources:

Frequently asked questions and answers about batteries • www.batteryfaq.org

“Batteries: How to Keep Them Alive for Years & Years…” by Windy Dankoff in HP69

“What is a Charge Controller?” by Windy Dankoff in HP72

Using the TriMetric (or other battery system monitor) to Maintain Your Battery System
www.bogartengineering.com/UsingTriMetMaintain.pdf

Thanks for contributions and photos from: Allan Sindelar & Mark Drummond, Positive Energy, Santa Fe, NM; Nick Lucchese, Sierra Solar, Grass Valley, CA; Roy Butler, Four Winds Renewable Energy, Arkport, NY; Ray Walters, SolarRay, Taos, NM; Tom Elliot’s Alternative Energy Information Center, Cover Mountain Ranch, CO; Matt Lafferty, Universal Energies Inst., San Francisco, CA; Jamie Surrette, Surrette Battery Co. Ltd., Springhill, NS, Canada; Joseph Marino, DC Power Products, Healdsburg, CA; Phil Undercuffler, Conergy Inc., Santa Fe, NM; Todd Cory, Mt. Shasta Energy Services, Mt. Shasta, CA; Richard Perez & Joe Schwartz, Home Power magazine

Comments (7)

bob tarzwell's picture

one trick for number 4 ie lots of batteries in parallel strings is to balance the charging with final wire size , I had acquired 80 good golf cart batteries and have 10 parallel strings in a 24 kw system , I balanced by voltage and current so each string gets very close to the same charging /discharge, I did it by reducing down a bit on the wire to higher groups , been 3 years now and still working great ,this year I will do a big charge and rearrange batteries in new strings to continue there life. in my other system its 120 volts 10 kw and two sets of 20 rolls s530's so not much to balance , works great especially when you get the charging right and charge hard.
ps after years of solar install I don't trust anyone's cable crimping I always scrimp and solder my connectors.

Woody Petrea's picture

Cool. Thanks for that. :)

Woody Petrea's picture

Was this article originally posted elsewhere?

Michael Welch's picture

As far as I am aware, only in our magazine. If it is out there elsewhere, it is most likely in violation of our copyright.

Woody Petrea's picture

It was just the way the article read. Under item #3 blunders, it states, "The photo at right shows a system that was ignored for more than two years." I noticed that all the images are at the top of the article.

Good read. Thanks to the author and to HP for posting it.

Scott Russell's picture

Fixed that text, Woody. We normally try to catch those references when republishing articles on the website, but they're easy to miss.

Michael Welch's picture

Ahhh. That's because the articles on our web site mirror the corresponding articles in the print version magazine. We generally try to avoid saying things like "to the right" and "on the next page."

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