Well, I can't really power off my car, because I go to places where I park and then stay for awhile. The car is not moving, so I can't vampire it for charging or I'd never get out. And the sites I go to are either primitive camping sites (basically they don't even have water, let alone electricity), or completely off the grid - for example, twice a year I camp in
Anza Borrego State Park, which is gigantic (the biggest by area), and you get to camp anywhere you like (no restrictions).
I bring along a DSLR, and I like to sometimes offload the photographs, but I don't need a laptop for that - these days you can get 64GB cards, and I have 3 of those, which is fine for weeks. I take a bunch of batteries for the various electronics, but leave 'em in the car. When I'm hiking far away from the car, I only have a backpack, and then it's an advantage to have it as light as possible, so I don't want to lug extra huge batteries and stuff - it gets old after a few hours and miles. Meanwhile it's nice to sit down and break out the laptop for some writing in complete isolation with nobody around for miles and miles and miles. Yes, paper and pen are neat, but when you have a structured software like screen-writing, it's not easy to reproduce on paper, plus you get spoiled... I'd get a cramp writing long hand... and then editing on paper(!).