The guy that I bought my 100s had some wires run on the outside of the camper. There's a + and - for the camper battery, along with a + run for power directly from the trucks battery. He had them on a toggle switch. I can have it so that the camper runs off my truck while driving, and it charges the camper battery. When I get where I am going I flip the switch and it isolates the truck battery so I am only running on the camper battery. For now I am putting the battery in the bed of the truck since that is where the wiring is. When I get the time I would much rather have the battery inside the camper. Even with the converter, water tank and electric water pump, that compartment is absolutely huge on my 100s. Might be a slight difference in design between the years though. It's tough with these 20+ year old campers, because who knows what the previous owner(s) did to botch things up?