Most campers need a good battery regardless of whether you are plugged into shore power or not. 1. The batter is necessary for the emergency breakaway switch to operate the trailer brakes should the trailer become disconnected form the tow vehicle. 2. Some trailers use the batter as a "buffer" between the converter and the circuitry to avoid over using the converter. 3. Most of the fridges and furnaces are controlled by a circuit board that depends on 12 volt power from the batter to operate properly. 4. Most of the lights in the camper depend on adequate 12 volt supply from the battery to function properly. 5. etc, etc. In short, you need an adequately charged batter for optimum performance from your camper.