My house bank of three AGM group 31's dropped to 11v in one day since charged. There are no loads, so I separated the batteries and tested the voltage. Two were between 11v and 12v, but one was below 6v. Apparently that is the cause of the problem. The thing I am curious about is that when I attempted to charge the suspect with two different chargers, one smart and one not, both chargers acknowledged that they were hooked up to something but did not start to charge them. The old dumb chargers analogue display needle, for example, merely moved to one amp rather than going up to its 6 amp rate. What would cause that behavior?
We have invested in a load checker. It will tell you if the battery is really dead, even if the voltage is right. Hit the check load button and if the needle crashes, it's dead. Sounds like that battery is dead.
Don and Cary
don't know...but a 6 amp charge seems to small to push a significant charge on a battery that has such a low voltage to begin with... 50 or 100 amp may do something but 6 amps seems like less than a knudge.
I would hook it directly by jumper cables to a 60-80 amp vehicle alternator and see if the battery didn't suck the nutz or squeal the beltz out of the alternator....
D&C- You are probably right that the battery is dead, but with Easter approaching I was hoping that there was a chance at resurrection.
Mr Eagle- I switched to an old 30 amp shop charger, which also seems to be putting out at about an amp or less. I guess I'll leave it on for a while to see if anything changes. I don't think that I would risk connecting it to my cars alternator though.
Lin,
I'm just thinking out loud here, but what has probably happened is that several of the plates in that battery are corroded and have collapsed together, dropping the overall voltage potential of that cell to 6 volts.
Your charger (even the dumb one) probably has circuitry to avoid overcharging a (much) lower voltage battery, so it's probably just looped to send only 1 amp, as a protection function of the perceived resistance at the other end.
I would avoid leaving that battery on there for too long, especially unattended.
If you continue pushing 12V to a (now) 6V cell, you could cause it to overheat and release hydrogen (in a sealed casing).
Although the glass mat material is supposed to sequester the hydrogen and not allow it to escape readily, too much heat might cause it to produce a lot of hydrogen and expand the casing or worse.
Good luck,
George
Sounds like the bad battery just shorted out inside. Probably toast. Can you cut it out of the string and still use the Bus Conversion?
George- Makes sense. The chargers are behaving like they are hooked to a fully charged battery.
HB- I am presently charging the other two batteries and have hopes that they are okay. Since are have not been traveling much, I would be fine to get along with them for now. I want the bus to be ready for use but prefer not to buy a new bank just to sit in the yard.