Hi, just checked out my battery bank and noticed one AGM.4D battery had a bad cell, only holding 10 volts after a long charge. ( this is a bank of (four) 12 volts in series for 24 volt system). All others are in good shape. Should I be concerned with drainage to other batteries ?

John.. just want it to be right!!!!!( without the additional replacement cost)

EASI54 wrote in news:EASI54.1f702d8
@boatbanter.com:

Hi, just checked out my battery bank and noticed one AGM.4D battery had
a bad cell, only holding 10 volts after a long charge. ( this is a bank
of (four) 12 volts in series for 24 volt system). All others are in
good shape. Should I be concerned with drainage to other batteries ?

Four 12V in series is 48V, not 24. Must be two banks in parallel of two
12V in series.

If this is correct, the two good batteries will drain themselves trying
to charge the bad cell, really cooking the good battery in series with
the bad battery in the process.....if that already hasn't happened with
the charging, which it probably has.



John.. just want it to be right!!!!!( without the additional
replacement cost)


You're dreaming, again....(c;

If this is 2 banks of two in parallel, to get 24V, and the charger is
still running, you've way overcharged the good battery in series with the
bad one... That cooked its unreplacable electrolye away so it's
destroyed, along with the bad cell battery. Replace both of them. This
now leaves you with two old batteries of reduced capacity in parallel
with two brand new batteries of more capacity. That'll be fine as long
as we NEVER leave the two old ones in parallel with the two new ones
STORED CONNECTED with no charger. Otherwise the new ones will be killing
themselves trying to bring up the old ones to their level....wasting all
4 in the process because it will never happen.

Nothing you do is going to be free.....in any case.

I'd dump all 4 AGMs for 4 L16H monsters all in series if you got the
vertical room for them. 375AH at 28.8VDC will crank most engines and run
a few lights...(c;

I think you're lucky the damned AGM batteries didn't melt the cheap
plastic case as they have no cooling with electrolyte like real
batteries. My Air Force truck had two 12V red AGMs in parallel when I
got it. One cell died and the good battery melted trying to get its
voltage up to 13V parked, stored, in parallel. The case physically
warped. I'm also lucky it didn't EXPLODE.

Larry
--
While in Mexico, I didn't have to press 1 for Spanish.
While in Iran, I didn't have to press 1 for Farsi, either.
While in Florida, I had to press 2 for English.
It just isn't fair.

[quote=Larry;533948]EASI54 wrote in news:EASI54.1f702d8
@boatbanter.com:

Hi, just checked out my battery bank and noticed one AGM.4D battery had
a bad cell, only holding 10 volts after a long charge. ( this is a bank
of (four) 12 volts in series for 24 volt system). All others are in
good shape. Should I be concerned with drainage to other batteries ?

Four 12V in series is 48V, not 24. Must be two banks in parallel of two
12V in series.

If this is correct, the two good batteries will drain themselves trying
to charge the bad cell, really cooking the good battery in series with
the bad battery in the process.....if that already hasn't happened with
the charging, which it probably has.

[color=blue][i]

Larry, thank you for the correction on my two battery banks in parallel for 24 volts. The other battery with the bad one is reading 13 volts and is holding a load well on a 100 amp volt meter. The other two batteries are holding 12 volts each but are of reduced capacity. Now what your saying is that if they are stored connected and with no charger on the other three will discharge till they equalize with the bad 10 volter??

John


If this is 2 banks of two in parallel, to get 24V, and the charger is
still running, you've way overcharged the good battery in series with the
bad one... That cooked its unreplacable electrolye away so it's
destroyed, along with the bad cell battery. Replace both of them. This
now leaves you with two old batteries of reduced capacity in parallel
with two brand new batteries of more capacity. That'll be fine as long
as we NEVER leave the two old ones in parallel with the two new ones
STORED CONNECTED with no charger. Otherwise the new ones will be killing
themselves trying to bring up the old ones to their level....wasting all
4 in the process because it will never happen.
Larry, so what your saying here is that the 13 volt battery in will discharge trying to bring up the
Nothing you do is going to be free.....in any case.

I'd dump all 4 AGMs for 4 L16H monsters all in series if you got the
vertical room for them. 375AH at 28.8VDC will crank most engines and run
a few lights...(c;

I think you're lucky the damned AGM batteries didn't melt the cheap
plastic case as they have no cooling with electrolyte like real
batteries. My Air Force truck had two 12V red AGMs in parallel when I
got it. One cell died and the good battery melted trying to get its
voltage up to 13V parked, stored, in parallel. The case physically
warped. I'm also lucky it didn't EXPLODE.

Larry
--