[rohrmann]

Seeing as you are installing a fuse block, and there will be fuses, connect the hot wire to the positive post of the batteries and the ground to the frame of the trailer. If you are worried, place a fuse large enough to cover the expected load being put on the fuse block. This should work well. I connected our TST signal booster to the load side of the small breaker on the wall behind the batteries, and I also added a couple 12 volt lights inside that compartment, connected to the same place, and everything works just fine.