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How to recover an overly discharged battery?

LagunaH1

Well-Known Member
Messages
3,703
Location
Lake Forest, CA
I have a Power Sonic 121100 B Battery in the Hummer. It’s connected to my radios, and is isolated from the trucks electrical system when the alternator isn't running. It’s been sitting in my truck while the truck was in the shop for a while (about 2-3 months) and when I finally got the truck back, the battery was showing a voltage of some 6 volts.
I have been trying to recharge the battery but regardless of how I configure my battery charger, I am unable to get the battery voltage to go above 7 volts, and my charger will produce an error message indicating that the battery is bad.
Is there anything that I can do to “recover” the battery to a state where it will take a charge?
 

JPaul

Well-Known Member
Messages
2,400
Location
Way up north, UT
Odds are, it's not worth it to try. In theory you'll want to check the levels in the cells and add distilled water, it might have dried out. Then try charging it again. I've tried this with a number of SLA's (nothing as big as that one though) and had mixed results. A lot of them were just too far gone to hold a charge, and the ones that did hold a charge didn't hold much of one.

You could try using a charger that isn't smart and will just dump power into it all day long. But I wouldn't hold my breath for a miracle. I would wager that one or more cells are completely shot.

I have to say though, 2-3 months is not long enough to run a battery that big to that low of a voltage on it's own, unless it was already shot before then. Otherwise you have a parasitic drain on that battery circuit that you'll want to chase down.
 

LagunaH1

Well-Known Member
Messages
3,703
Location
Lake Forest, CA
Well, I did put a "dumb" charger on it for a few hours and it's now sitting at 11.89 volts. From here, I'll use my regular charger and see what I can get it to
 
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