The battery banks are the primary source of electricity to the trailer, whether or not it is hooked up to an input source like a power cord. The batteries provide both DC power (directly, as they are DC 12v batteries) or AC power, through the inverter that converts it to household 115v AC.
The trailer will have two independent power networks, one 12v DC and one 115v AC. There will be standard wall outlets for the AC power, and 12v receptacles (like in your car) for the DC, and maybe some built-in USB outlets, though the ones I've found so far are low amperage and the ubiquity of car chargers makes that less critical.
Since there are two power networks I have two breaker panels, both from Blue Sea Systems:
The DC panel is Blue Sea 8081, available from several online vendors. The AC panel is Blue Sea 8043.
I mounted them through a piece of plywood that will be hinged so I can get behind it to work on the wiring as needed.