7 Pin with auxiliary wire. 30 amp fuse. Battery isolator.
Notes: Aux hot will drain trailer battery. Vehicles max draw 5-15a (not the 30a fuse that is recommended). Must isolate trailer from vehicle when not connected. Trailer: isolate aux power from battery.
Absolute best is to not have batteries on your trailer at all. Battery power supplied from vehicle via 2ga wires ran to the back (not very rental friendly and prevents friends from borrowing).
