Battery Installation and Maintenance: Page 4 of 4

Signs of a Bad Battery

While an almost unlimited number of things can go wrong in a battery bank, there are a few signs and symptoms common in RE systems:

• The batteries complete a bulk/absorb charge cycle, but voltage plummets as soon as you stop charging and add a load, which indicates reduced capacity. Sulfate buildup has occurred and the batteries may be nearing the end of their life.
• One cell is different (voltage or SG readings; corrosion; appearance) from the rest often indicates that it is failing.
• Bulging cases are typically a sign of flooded batteries that have frozen. The frozen electrolyte expands and causes the cases to bulge, often forcing terminals and plates to warp, and cases to crack.
• Overheating or overcharging sealed batteries can cause cases to cave in. Excess pressure builds up inside the battery, and gasses escape through the safety valve covers. When the battery cools, some of the electrolyte is missing (from off-gassing) and the decreased pressure causes the cases to cave in significantly.
• Melted lugs/battery terminals could be the result of resistance from loose connections or corrosion buildup.

Recording

One of the best ways to track your batteries’ health is to keep regular, precise records. During your maintenance checks, measure individual battery or cell voltages, and check specific gravity for flooded batteries. Ideally, readings should be taken after the batteries have been at rest for 12 to 24 hours and are fully charged, but this is generally impossible in an off-grid situation. Checking after 30 minutes of rest (no loads, no charging) will still give you good information.

These checks can alert you to bad cells, or let you know if the entire bank may be on its way out. Any differences in cell voltages or SG indicate you may have a failing (or failed) cell, and checking your readings against the expected SOC will tell you if they are losing capacity. The sooner you spot a problem, the more likely you will be able to fix it.

Access

Lena Wilensky owns Nunatak Alternative Energy Solutions, a small RE design and installation company in the mountains of Colorado. She is a Solar Energy International instructor, a NABCEP-certified PV installer, and is certified by ISPQ as a PV Affiliated Master Trainer.

Further Reading:

“Managing Your Batteries” by Dan Fink in HP142

“Battery Box Design” by Allan Sindelar in HP141

“The Top 10 Battery Blunders—And How to Avoid Them” by Windy Dankoff in HP114

RE Battery Manufacturers:

Concorde Battery • www.concordebattery.com

Crown Battery • www.crownbattery.com

Deka/MK • www.dekabatteries.com

Discover Energy • www.discover-energy.com

Exide Technologies • www.exide.com

Fullriver Battery • www.fullriverdcbattery.com

Hawker • www.hawkerpowersource.com

Interstate Batteries • www.interstatebatteries.com

Solar-One/Enersys • www.hupsolarone.com

Surrette/Rolls Battery • www.surrette.com

Trojan Battery • www.trojanbatteryre.com

Universal Power Group (UPG) • www.upgi.com

U.S. Battery • www.usbattery.com