Originally Posted by rollingsmoke
Jim, sorry again for not giving enough information up front. The house batteries are 12v wired in parallel. They're Optima AGM Yellow Tops so there's no water level to check.
I left the one house battery hooked to the A-C relay for about three hours last night and the voltage had only increased to 5.98v. I checked the temp of the A-C relay and it was hot so I checked it with my handy dandy calibrated barbecue thermometer and the back of the housing was reading 110*. After that I disconnected everything and closed it up for the evening.
After the sun gets up, I plan to isolate the other house battery and do the same thing as I did with the first one.
I would not strike me as unusual for the solenoid to overheat when you're trying to charge a battery with a shorted cell.
In future, if you have a battery in your RV that's that low, disconnect it from the RV and try to charge it with an automotive charger. In order to protect expensive devices in the RV...like the converter.
Since you have to replace one of those AGM batteries anyway, consider switching to 2-6V golf cart batteries. Because if one AGM failed, the other one is probably on it's way out too.