Auxillary Battery in Enclosed Trailer to Power Interior Lights  

I have a 24foot enclosed car hauler. There is an array of interior lights which run off the tow vehicle when the vehicle is running or in the run position Ford F150 w/ factory isolation relay. I have an aux. battery in a battery box which is used to power a winch. Id like to wire this battery up to the trailers electrical box such that it can power the interior lights when the trailer is not hooked up to the tow vehicle or the vehicle is not running. Here are my concerns: If I simply wire the battery to the 12V power wire in the 7-pin harness, this harness would be hot at all times and I worry about the possibility of shorting due to water getting into the open-end of the trailer harness while in storage/not in use. I also worry that while the winch is being used and the truck running, that I could be drawing power from the vehicles battery during high-load situations. I also have concerns that the break-away battery will now be tied to my winch battery since they share the same 12v connection. Will this be an issue? I thinking that installing a high-power diode such as the Roadmaster Hy-Power Diode # RM-790 is the best solution such that I can isolate the winch battery from the rest of the electrical circuit and not have power flowing to my break-away battery or keeping the trailers 7-pin harness hotinch which still being able to maintain the winch battery when the tow vehicle is hooked up. Id like to get your expert opinion on the matter. Thanks!

asked by: Jay