Extra power source
 

Soon to purchase an econoline passenger van to use as a weekend camper. I don’t want to remove all the interior like many van folks do. I will likely just take a seat or two out to make a sleeping space maybe add some insulation as well. I am wondering if I can wire an externanal power source such as a jackery or eco flow into the van in a way that I can use existing accessories while parked. I would mainly like to use the stereo, interior lights and rear AC/Heat Fan (on vent only) to move some air around inside.

How would I go about doing this?