I've been going thru the rig, doing routine maintenance stuff. While doing, I had the shore power disconnected. Didn't want any unexpected sparks should I accidently cross some wires somewhere. Anyway - hooked the shore power back up yesterday afternoon and the coach battery started giving off some strong sulfur fumes. Checked the converter/charger output and it was 13.75 volts - which seems about right for charging up a 12 volt battery. Also the battery was warm to the touch. Not uncomfortably hot, but warm. Am I worrying too much? I'm getting ready to change over to two 6v golf cart batteries as recommended in everyone's previous answers - thanks! - as soon as I do some modifications to the battery box.