Battery System Maintenance and Repair: Page 3 of 4


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Battery System Maintenance and Repair
Regular care of your renewable energy system’s batteries will help ensure that they can provide years of high performance.
Add distilled water to the batteries
Add distilled water to the batteries to about 1/4 inch below the bottom of the fill tube. Always wear eye and skin protection.
Corrosion between a battery terminal and the metal frame of a battery rack creates a potential path for current, which could create a ground fault or shock hazard.
Excessively corroded battery connections
Excessively corroded battery connections can have enough resistance to affect a battery’s performance, both when charging and discharging, and result in reducing a battery’s performance and life.
Clean all battery terminals and cable lugs
Take the time to make all battery terminals and cable lugs clean and bright before connecting the cables.
Petroleum jelly can protect terminals against corrosion
Petroleum jelly can protect terminals against corrosion, but also may attract dirt and makes using a wrench on them messy.
Always use insulated tools when working with batteries
Accidental short-circuiting between battery terminals can damage a battery and result in severe injury—always use insulated tools when working with batteries.
A battery meter
A battery meter is crucial to monitoring your battery bank’s electrical state.
Keep good records
Keeping good records is part of good battery maintenance, and can help you identify trends and spot problems if they occur.
Overcharging can result in excess gassing
Overcharging can result in excess gassing and loss of water. Exposed plates will oxidize and the battery will be permanently damaged.
Undercharging can result in electrolyte stratification
Undercharging can result in electrolyte stratification and/or sulfation (shown) and a damaged battery.
Battery System Maintenance and Repair
Add distilled water to the batteries
Excessively corroded battery connections
Clean all battery terminals and cable lugs
Petroleum jelly can protect terminals against corrosion
Always use insulated tools when working with batteries
A battery meter
Keep good records
Overcharging can result in excess gassing
Undercharging can result in electrolyte stratification

During the monthly or quarterly maintenance checks, measure and record the battery’s voltage and each cell’s specific gravity. A SG difference of 0.025 or higher between cells indicates an equalization charge is needed. To perform an equalization charge on an FLA battery:

  • Draw a diagram or label each battery cell with a reference number.
  • Charge the batteries through the bulk and absorb stages before starting the equalization process.
  • Measure and record the voltage and SG of each battery and cell.
  • Choose the cell on each battery string with the lowest SG reading as a pilot cell—these will be the cells tested to determine when equalization is complete.
  • Check the electrolyte level in each cell to make sure the battery plates are covered.
  • Initiate the equalization charge.
  • Check and record SG readings of the pilot cells every half hour.
  • Check electrolyte levels to ensure that they never fall below the top of the plates.
  • Check temperatures of the batteries’ electrolyte every 30 minutes to make sure it never exceeds 125°F (52°C). Stop equalization if this temperature is exceeded.
  • Stop equalization when the SG reading in the pilot cells stays constant for three readings.
  • Water each cell to 1/4 inch below the vent tube and replace the caps.

Not all users will want or be able to check the electrolyte’s SG on a monthly or quarterly basis. A more general method is to set a predetermined routine equalization maintenance on a monthly, quarterly, or biannual basis without checking either voltage or SG. To keep it simple once the equalization process has started, charge time can be set depending on the battery bank and charger’s size, and how often the batteries are charged to 100%. The amount of time typically will range from two to five hours.

Daily Monitoring

If it’s your first time dealing with a battery-inverter system, it will take some time to understand the ebbs and flows of the system’s readings in a “normal” day of charging and discharging, and recognize if something is wrong. Checking the battery’s voltage and state of charge every day can provide a valuable orientation to the system—you’ll begin to understand what is (and isn’t) normal.

Monthly Maintenance Checklist

Using a monthly battery-inverter maintenance checklist can help you stay organized and help you pinpoint recurring issues with your battery system.

  • Battery/Inverter:
  • Clean corrosion from battery terminals and cable ends.
  • Clean tops of batteries.
  • Clean the inverter fan filter.
  • Check electrolyte levels, and add water if necessary.
  • Keep track of water additions—an increased need for water may indicate increased cycling or a failing battery.
  • Check to see if surge (lightning) protectors are intact.
  • Check inverter(s) for error and event indicators.

Comments (10)

cliffgrimes's picture

I have a battery bank where one of the batteries appears to have a bad cell. The SG is low and the voltage across the battery is only 4.2v, these are 6v Trojan L16s. The rest of the batteries are in good shape - SG is good and voltage levels are consistent. I am going to replace the bad battery with a new one, fully charged. My question is, after I do that is there anything I should do for the entire battery bank?

Michael Welch's picture

Have you tried a full, 8-hr. equalization on the battery bank as it is? The cell may be weak, but without occasional equalization it will steadily get worse and worse.

If you end up replacing the battery, use the bank a few cycles as a break-in then go ahead and perform a full equalization on the bank. That will bring the older batteries up as close as possible to the level of the new battery. But if your battery has multiple strings, the bank will never be better than the lowest-performing string, even with a new battery within one of the strings.

Marsha Robison's picture

I hear you Eric. But I am in a very harsh environment. Temps range from 0 in the Winter to 109 (sometimes) in the Summer. One day can have ranges of 70 degrees. My battery banks just don't preform as expected, even with diligent maintenance.
Please let me know your expert opinion on the Lithium as an alternative. I have been watching this technology but want to wait till it is perfected. Are there any other options.

Ed Mahoney's picture

I've supplied thousands of systems thoughout the world; many in extreme temperature environments. Your problem is not unique.
In high temperatures batteries will suffer extreme loss of useful life and in cold temperatures their capacity is diminished.
If the air temperature canot be controlled the best method of solving the high & low temperature extremes is to BURY the batteries in a container. Getting the batteries a couple of feet undergroung will minimize the temperature effects. You can reduce the battery's temperature by 25 F. in hot summer months and increase it by 25 F. in cold winter months.
In addition, use a battery temperature compensated charge regulator to optimize the charging voltage.
By doing this your battery will last at least 50% longer and help provide it's maximum capacity.
If you need further assistance please let me know.
Ed Mahoney

eric roberts's picture

Hi Just a point to Jim and Elaine stack? Lithium batteries have no history yet? we do not even know how to dispose of them yet, they can be highly toxic and a fire hazard, but i understand what you mean about, lead acid batteries, which are incidentally 95% recycled now. thanks eric roberts

Jim and Elaine Stack's picture

Use lithium batteries and you never need to water, they last much longer and are non hazardous. It's the 21st century and we have taken lead out of paint and even gasoline so don't use it.
Just mining it kills us. People say it gets recycles but that is a poor excuse since it gets in the air and everyplace. LEAD is one of the worst containments ever used.
Solar City used Tesla Lithium batteries for backup. Tesla is building a new battery factory that will make them 30% better or more in a few years. Invest in the future not the past.

Paul Hancock_2's picture

Great article!

I was recently moving my inverter and inadvertantly the pos and neg battery leads touched momentarily causing some sparking while they were on the ground. I know this is not good for the battery bank (I have 12 surrettee S-530s) but is there any specific way I can test the batteries to see if they sufferred any permanent damage?

Michael Welch's picture

Hi Paul. Just minor quick sparks? Should not have affected the batteries at all.

Paul Hancock_2's picture

Thanks for the reply Micheal. The sparking was just for a second or so but did melt a bit of the copper connector on the end of the cable. Batteries seem to be performing as usual but would you recommend any maintenance or testing I should be doing after this incident?

Thanks again.

Michael Welch's picture

Just go ahead and use your batteries. Rest easy, you have not harmed them.

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