After being setup for 10 days with electric hook ups; this morning all of the sudden the 12 volt lights dimmed and stayed dim.  I went out side and checked the 12v breaker, sure enough it had tripped.  I reset it and then smelled sulfur.  I opened up the battery compartment and one of the batteries looked like a steam iron it was out gassing badly.  I could hear the fluid bubbling inside of it.  It was hot to the touch.  I unplugged the converter/charger and left the compartment open to vent the gas.  After an hour I felt it was safe to remove the battery to replace it.  New battery and everything is back to normal.