I am customizing my Enclosed Cargo Trailer/Plane Hauler; I think I know the answer, just looking for confirmation; presently, the Running Lights, Tails Lights, Marker Lights, etc, run off the Vehicle Pulling the Trailer via the 4 wire Vehicle/Trailer Plug, and these lights are all grounded through the metal frame of the Trailer; I want to install a separate stand alone 12 volt system that is independant of the towing vehicle, will have its own battery, on board charger, etc; to power Trailer Interior Lights, Chargers, etc; can I ground these to the trailer Frame if I ground this Independant battery to the Metal frame as well, or do I have to run a ground right back to the battery and not ground the battery to the Frame?

Thanks.