I am also interested in a larger source of DC power so that I can use the
cabin lights and have things turned on while cleaning/troubleshooting ect.

Why not make a battery cart with large truck or tractor batteries? I have used
several of those over the years most home made. One even used a marine rotary
switch that when wired correctly allowed the user to select either 12 or 24
volts. That one used just two batteries mounted on a welding bottle cart. It
also had a battery charger permanently mounted and connected. When not in use
we kept it plugged in.

John Dupre'