Battery hot while in charger

[MV Mystery]

Installed a new Victron 15 amp charger for my generator/Minor house bank. Left overnight , but one battery is extremely hot in the bank . Any ideas? The charger is connected positive terminal of the warm battery, negative to the other cooler battery.( The bank is 12v and comprises two 70 amp hour batteries connected in paralell). The charger itself was showing in the ABS phase when I arrived today.

 

[Captain Ralph]

Usually a sign of a low or bad battery. First SWAG, a bad cell.

If it is still in Absorb mode, I fear something is not rite with that battery.
IMO, should long ago be in float mode.

New charger? Problem with the first charger?
Looks like fresh batteries. Sadly,, New or fresh batteries do have problems.

Disconnect the batteries and charge one at a time.


Do you have any load testing devices?
Put a toaster on them both (separately), I bet that warm battery will roll over and die.

 

[MV Mystery]

Thanks for your reply. Had a feeling a bad battery, but it's a fire hazzard. If I didn't check today, what would be the outcome if the Victron charger continued to stay in that mode.
I assumed smart chargers solve this issue. 40 years ago in my father's boat with non smart charger, it was simply on a timer.

 

[Pascal]

I don’t think traditional batteries can start a fire. They can explode spraying acid everywhere if you don’t have covers on the battery boxes.

I m trying to understand how you would connect a charger to two batteries in parallel and I wonder if that a really the best way to do it. Two batteries in parallel are essentially two banks. It seem that it would Be better to use a multiple banks charger and connect each battery to its own output.

 

[MV Mystery]

The Victron literature is sadly lacking in technical detail. This charger has a 3 output capability.
So my two batteries are connected pos to pos and neg to neg to maintain 12 V as one bank. It starts my forward generator and runs instruments and minor house systems as I have
two separate 24v banks for main engines and major house systems. . Are you saying that I could use two separate charger outputs - one to each battery in the same bank?

 

[Pascal]

It seems to me that it would allow the charger to better regulate output to each battery. I would try to ask victron which way is best

Although now that i m thinking about it when installing an inverter charger on a set of batteries in parallel, they are connected as you described

 

[Captain Ralph]

If they are in parallel, it is one bigger battery. But when one battery fails, it may bring down the other(s).