LFP 12 V battery problem

[kjfishman]

I powered my fish finder in my Loon 126 with a Lithium 12v 7 ah battery.   I managed to roll the yak and submerge the the non-waterproof case. Now the battery won't charge past 9.7 volts even after 14 hours on the battery charger. These batteries have circuit built into the battery anyone know how to reset them?  The battery is a LIFEPO4 12V 7AH.

[Tennessee Boy]

I don’t think the BMS needs to be reset because you are able to charge it.  My guess is the water ruined one of your cells.  These batteries typically have four 3.2 volt cells.  You have 9.7 volts fully charged which is what you would expect with only 3 cells.  I would expect to see no voltage when the charger is disconnected but every BMS is different.

 

A small battery like yours may have multiple small cells grouped together in parallel to make what I’m referring to as a 3.2 v cell. If one of these small cells shorted out it would short the whole group.

[Bankc]

I agree.  That sounds like a bad cell.  It's odd that it would fail because you got it wet.  They're usually sealed up pretty tight, which also makes working on them almost impossible.  So you probably just need to buy a new one.  If it was an expensive, name brand one, you might contact the manufacturer and see if they'll warranty it.