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Registered Member #973
Joined: Tue Aug 28 2007, 07:32PM
Location: Pittsburgh, PA
Posts: 66
Hello all. About a month ago i built a battery desulfator ( i built the N Ch. mosfet based one) to help revive some old batteries i found in my garage. i have about 3 of them that i am circulating on a Charge/Desulf. schedule. Things have been going well. Each time i recharged a battery, it's max power output increases, which is what i am aiming for.
My problem is this: I had a 12V 7.2Ah 6 cell lead acid battery charging overnight and into the day. I forgot to turn off the charger for the next night, and before i fell asleep, i heard a soft whistle for about a second. I concluded after that it was a cell venting (build up of H and O ??), posibly because i had it charging at around 14.5V (from the nominal 13.8). My problem now is when i charge it, the charge current is incredibly low (.08amps, compared to the usual .7 to .8 amps before), and the measured voltage after charging with 13.8 votls now only reads around 10.6 (the one cell seems 'dead' apparently). Is the battery cell dead now? Is there a way to fix it? I have googled for an answer, but found nothing, so i came here. Any help with these questions would be great, and feel free to correct me on anything i've said wrong.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Yep, that battery is dead. The failure mode is loss of electrolyte, unfortunately with SLA's this is not possible to fix as the electrolyte is already "starved" and further loss causes the gel to shrink away from the plates..
Also possible that something gave way inside the battery (probably an internal busbar). regards, -A
Registered Member #396
Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176
I had something similar happen, except mine had a very threatening looking bulge in the side. Pretty scary to handle, and it never worked properly again.
Registered Member #973
Joined: Tue Aug 28 2007, 07:32PM
Location: Pittsburgh, PA
Posts: 66
i found a couple of gaint 17Ah batteries from an old UPS and they all were bulged out to the point where i could see inside them. got rid of thsoe before they leak or something nasty of the sort. this small 7.2 Ah one is the newest one i had and now its dead. crap. as for the others i am reviving them and they are doing well. the desulfator is happily pulsing around 60V at 1kHz into some of the older batteries, and each session the voltage decreases, which is good by what i've read.
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Lead acid battery charging problem
