When I did my skid house, I bought an actual fuse block and grounding block from NAPA. I ran 10 Gauge wire to the two blocks and 16 gauge to the LED lights(mandatory) and cigarette lighter/USB combos. If you decide on getting a fan to push the heat down, go with computer fans, the cheapo 12 volt vehicle fans are a huge amperage draw. For the battery I would not go any less than a model 27 Interstate battery. If the Inside is already finished Home Depot has the Cable management tracks that you can hide your wires in. Hope you have a good time in your new Shack.