2002 Discovery Trailer wiring specific question. I installed a new 7 pin trailer socket and have it all wired up and working. I ordered a brake controller and will install that when it arrives.
I will be mostly towing my dump trailer and would like to have the 12v charge wire in the 7 pin to charge the dump battery while the disco is running.
I’m assuming it would be best to run a heavier gauge wire to the socket like 10 gauge. What is the best way to do that and have it only on with the key.
is there a spot in the engine fuse panel (spare) to run from or do I need to connect to the battery and install my own circuit breaker/relay setup?
I see there is a 30 amp AUX in that fuse panel, is that a possible source?

Thanks!