Depends on what you want to run off batteries. I removed the factory converter, and installed an inverter/charger in its place. Remove the factory power cable from the breaker panel, install it in the inverter/charger, and run a new power cable from there to the factory panel. Inverter now power everything on the trailer. In my case I ran the power cable to a new sub panel, then from the panel to the inverter/charger. I moved the electric water heater, and both ac's to the sub panel. Now everything but the ac's and electric water heater run off the batteries when AC power is not available. I also ran 4/0 cables from the batteries to the inverter/charger, mine is a 3kw unit, large enough to run coffee pot, toaster, tv, and microwave at the same time. It also charges up to 150 amps in bulk.