I'm having problems with my two coach batteries this time around (last week it was my chassis battery). My two coach batteries are around 4+ years old. My wife heard a sizzling noise and could smell the batteries. When I opened up the step on my Winnebago one of my coach batteries had steam coming out the refill caps. I immediately took both coach batteries out of the battery holder. One of the battery cases was hot the other was warm. I'm going down right now to buy 2 new batteries! Can anyone tell me what is causing my battery to boil? I don't want to put the new ones in and have them boil!

That is because they are charging. What was the voltage reading?

Probably a bad battery. When they are that old the sediment in them can build up and cause plates to short. Had it happen in a battery in one of our Winnebago's a few years back.

Yes, you are wise to be concerned . Can you check the voltage output of the terminals coming from the converter/charger on board? That may tell the story. Do you know if the water level on the two batteries was alright?

The one that was HOT probably has a shorted cell.....or two.If the two batteries are both 12V and in parallel, a shorted cell in one will show up more dramatically than it would in a 6V used in series.

A shorted cell in one battery will cause over charging in all. Replace them both and be done with it. Extremely dangerous as the gas released is explosive.

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