House Battery Overheating!

[98winnie]

Had the motorhome plugged into shore power overnight. This morning I felt heat coming from the step where the batteries are stored. One of the batteries was HOT and water boiling! I have a '98 winnebago gasser with two house batteries. Only one is overheating. I unplugged shore power and turned off the house batteries. Any idea what caused this??
Thanks

[Kahoona]

Unsure of the exact cause, possibly a dead cell. You did right to turn them off and unplug but what you need to do is disconnect the battery to stop charging voltage from getting to that one. If they are 12v batteries you can just remove the hot one and reconnect to the good one. Go to or take it to a auto parts place like NAPA and they will test them for you. I would also test the output of the charger just in case. If it is batteries you need 2 new ones. Deep cycle only, 2 6v deep cycle golf cart in series would be better than 12v. Please let us know what you find out. You might want to rinse out that compartment with soda water to remove the acid too.

[1st-tt2018]

Originally Posted by 98winnie

Had the motorhome plugged into shore power overnight. This morning I felt heat coming from the step where the batteries are stored. One of the batteries was HOT and water boiling! I have a '98 winnebago gasser with two house batteries. Only one is overheating. I unplugged shore power and turned off the house batteries. Any idea what caused this??
Thanks

Probably have a bad battery now, but you know that already. I would bet the other one has a bad cell or two. I would check connections and ensure your charger hasn't fried. (Too much amperage for SOC...

[98winnie]

good thing the batteries are under the step or i might not have noticed till too late. I'll run it up to the parts store and see what they say.
Thanks

[Al Bundy]

Battery is sulfated.
Time for new ones.
You should have just unplugged from outside and waited till all the hydrogen gas was gone
You're lucky something worse didn't happen when you switched off the batteries

[98winnie]

Yes I'm very lucky.
I just had it plugged in at the house. There is a ford dealership a few miles from me. I'll just take it there. Checked the stickers on the batteries. Both are 5 years old so need to change out. I need an oil change too so might as well get that done as well.

[153stars]

IDK if it's true or not, but someone posted Sams would have 6v golf cart batts. On one day sale for $20 that would put them at like $68 . They did have a $20 off sale on car batts a while back for at least 2 weeks Not to get into the usual battery debate but if they last 5 yrs that's hard to beat .

[Waiter21]

Verify the output voltage of your converter.

I replaced my single stage converter with a more battery friendly 3 stage converter..

The converter switches modes, It starts charging at 14.7 volts, then as the battery is starting to reach full charge, it reduces the voltage to 13.8 volts. When the batteries are fully charged, it goes into a trickle / maintained mode with the voltage at 13.2 volts. This prevents the batteries from being boiled to death.

Need to upgrade Coach 12 volt power system – 1999 Southwind 35S


I also performed some battery and wiring upgrades to better accommodate our boondocking needs.

Upgrade Coach 12 volt system – 1999 Southwind 35S


..

[98winnie]

before i start battery replacement, I noted a post in this thread that said I might try 6v instead of my current 12v. I'm not familiar with 6v batteries. Do I need 4 6v to replace the 2 6v? Space is limited under my entry steps.

[Al Bundy]

Two 6 volt batteries wired in series to make 12 volts
They'll be taller so make sure you have enough room for the extra height

[Mark_K5LXP]

Odds are pretty good two 6V batteries would be more capacity than your two 12V batteries. The only reason I wouldn't use 6V is if they don't physically fit, otherwise they're a more robust and economical solution.

Mark B.
Albuquerque, NM