I guess I will ask why not put a battery in a box ont he trailer? I mafe a lockable box for the tounge of my trailer, mounted a battery in a battery box inside and ran a cable grom the battery on the truck to a quick connect at the trailer plug that connects the trailer battery.. Winch is hooked to the trailer battery and the truck charges the battery on the trailer for me. I have an 8000lb winch so I can drag all the junk cars I buy and shouldnt