Got some onboard electrical going finally. I have an older 40 amp float charger - you can just leave it plugged in.
I am treating the lighting in the bus sort of like a car, they are connected to the coach batteries not house batteries. There is a relay setup that connects the coach batteries only if the charger is feeding the system, or the engine is running.
The relay is latched to the vehicle power too, so you can unplug from shore and lights stay on for a while until you start engjne, but they will power down if you don't do anything for a while.
I think right now the hardest thing is deciding on light placement, so I have some wires stabbed into DC power to test light fixtures. I'm trying to make most lighting secondary reflective.
Pretty sure it gets more complex once I have house batteries, solar, generators, hamster wheels, etc.