I fought the discharged battery fight for years with my trailer winch. Finally threw in the towel. Got one of those high amperage disconnects and ran a positive copper lead all the way to the truck batteries (Cummins) with a charger style clamp. The negative side I got a welding disconnect and bolted it to the hitch for the negative connection. Haven't had a problem since. Can't remember what size cable I used but it was around a 1/0.

"We live in a time when intelligent people are being silenced so that stupid people won't be offended".