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Need help with gel batteries


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I was given three Deka Solar batteries 8G27 from work because they thought they were dead. They were powered by a solar panel that never saw sun so they were eventually discharged to 10 volts or so. I brought them home and charged them. One of them holds a charge and after resting will read 12.7 volts or so. The other two after a load has been put on them or after resting awhile read 12.3 volts. Am I doing something incorrectly or is the battery worthless? I thought a bad cell would show it around 10 volts so I'm not sure what's going on. Any help is appreciated. Thanks.

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It sounds like they are holding a partial charge. 12.7v is nominal. 12.3v is around 70%. 10v is absolutely "0". So it sounds like they are holding a bit of a charge, but along with that is capacity. A battery "can" hold a 12.7v nominal charge, but as soon as a load is applied can drop to nothing. If each has been fully discharged for any length of time, and depending on how old they are (ie., 4-5+ years old), it might be worth taking the 12.7v battery in for load testing (generally free) just to see what kind of capacity it still has, but the 12.3v batteries I would junk.


A "bad cell" is relative. They aren't "dead", per se, but likely have no practical useful life left in them.

Edited by Yarome
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How much of a "load" did you put on the battery to see the 12.3V reading??? A fairly heavy load will drop the voltage from 12.7 to 12.3 on an otherwise good battery.


On re-reading the OP I see they are going to 12.3 after resting. They probably are "toast".


For a good test, I would hook up each battery to my RV and turn on 6 incandescent light bulbs for a load of about 9amps. Leave the lights on for about an hour turn off the lights and check the battery voltage. It should still be about 12.5-12.6V.

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