Battery overheating

Battery overheating on shore power usually means battery overcharging.
But it can also mean other things (Example shorted cell)

Measure the voltage at the battery both when overheating and again, 1/2 hour after you either unplug from shore power or turn off the breaker that feeds the converter.

Page 2: One of the things I learned this week the a danger of SEALED lead acid batteries (Full name Valve Regulated Sealed Lead Acid) this inlucides AGM and Maintenance free designs, in fact all Maintennace free designs (Of which AGM and GEL are sub sets).

In normal battery operation water is converted into it's elements Oxygen and Hydrogen, and in SEALED designs these are re-combined internally.. This, generates heat. Vented liquid filled (Flooded wet cells) the gasses escape and likely re-combine later under other conditions. But the heat is NOT confined to the battery housing.

When these things happens its almost always a bad battery. Wolfe gave great advice to help troubleshoot. As far as water level goes, use distilled water and put in enough to just cover the plates. Then charge overnight and recheck level. If you fill a discharged battery to the top it will spill over when charged. Water level goes up when charged and down when discharged.

No point in guessing at the problem.

In order:

Verify water level in the batteries.

With a digital voltmeter, verify what the voltage is AT FLOAT LEVEL (smart charger) or after plugged in overnight. Should be 13.2- 13.5. If different and a smart charger or inverter charger, verify programming.

With a HYDROMETER (under $10 at auto parts houses)check SG (Specific Gravity) of all cells. If one is low, it will cause a perfectly good charger to overcharge the remaining good cells.

And, if the battery case has swelled, it is quite likely that the battery is bad.

You may have a bad charger or bad battery or both.

I went through a couple of sets of batteries where one would go bad and the charger kept trying to charge so it overheated the batteries. These batteries were only a couple of years old. The battery shop tech said the plates are so thin in batteries now days, that a good bump will cause them to short. Once I replaced the set no more overheating.

Bummer