[DebNJim B]

I bought a 1 year old RV once and the dealer installed a new battery and gave me the old one. I hooked them up in parallel and ran that way for a couple years. Then one night in the middle at about 2 Am the gas detector went off. After a brief search I found the older battery was boiling over and the hydrogen/sulfur gas set off the detector. I guess a plate warped and shorted out but I never had it tested, I just discarded the battery. I later learned (from this forum) that you should always use matched batteries if you run in pairs.