Wow thanks to all of you for the very detailed replies, especially you, @Powderhorn !
Looks like I’ll save your answers and keep them in mind for when I have the nerve to deal with all that effort (we had the idea of installing solar panels on our car roof and buffer it to a second car battery for extended camping trips)
It’s definitely a rabbit hole. What I can recommend as first steps if you’re considering a vehicle solar setup is a two-pronged approach: determining what will be electric vs. some other fuel source and getting a usage monitor like a Kill-A-Watt for devices you’d be planning on using during those trips.
Hard numbers on capacity need are crucial when starting to put together a system. Everything else stems from those figures. Good luck!