We are having the same issue with our Rockwood Signature lite. As long as the camper was hooked up to the truck everything worked fine. Unplugged quickly the battery would go bad. (and we were plugged into electricity) After much troubleshooting we finally called the dealer and the service guy figured it has to be our converter. We are getting it replaced on Monday. Oh, and the TV in the living room decided to die on us as well. It was a rough start to a short vacation.
Also -- bruceatlam is correct, you need to hook up to a battery charger. Or stay hooked up to your vehicle. That is the only way we made it through until we got home. I had no idea of how important the battery was. Your refrigerator will not run without a battery, even plugged into electricity with the gas option turned on. Also, the awnings, slides, etc. won't work.