Trailer wiring help

I would not bet on it.

You have to realize the situation you can get into in a deal like this. Let's say you just got done on a nasty job. Maybe you broke the rear axle. Maybe the front suspension got damaged. In other words, you just loaded "the car" and it REALLY took some pullin.

So the winch has REALLY used the trailer battery, and now it's REALLY pulled down.

That battery is really going to want to "suck" current on that 30A line. It might warm things up, and it might blow the fuse.

Not knowing just how good that line was wired I'd probably want something I knew was "a little better" such as minimum no8 or better no6, and put a giant "max fuse" in there

"Charts vary" but 50A for no 8, 80A for no6

I would take a GOOD look at the under-hood alternator wiring before deciding where to tie in "up front."

Also bear in mind that along with hooking up the trailer "charging line" you are going to want the GROUND upgraded as well. A dedicated no6 from the trailer frame / trailer battery NEG direct to your pickup frame would be good, but I don't know "how" you would pull that off

Perhaps some of the quick connect welding cable connectors?