Don't know what type brand model year or style RV you have, but if it has a set of 6 volt and a set of 12 volt batteries, then you likely have your house battery voltage already up at the dash. You can just wire to that. If you have a class A RV (and maybe even a class C), there's likely a switch on the dash that you can throw that automatically powers the radio from the house batteries. And yes I'm aware that we're in the Class C thread, thing is that people often post in the wrong place. So if you don't mind, it would help if you'd put specifics of your RV in your sig.