Want to add a battery to my truck camper - help please

My camper doesn't have a battery either.

I put one in a plastic battery box and in the truck bed on the driver side front corner. I made a custom cable that goes back to the 7 pin connector on the rear hitch, and, plugs into the front of the camper.

Do a search. Lots of folks have batteries or second batteries in their beds. It's an easy solution.