What are your tips for working offline?

I am working from my 2010 camper-van for several months in the summer on a 15.6'' thinkpad. My main issue is/was battery duration when I am off grid. Typically I had to move after two or three days just to fill up the battery by driving. Last year, I used a folding solar panel together with a powerbank, but that was not really efficient, because it was often too cloudy. So for this summer I bought myself a 300 Ah battery and hope that this gives me at least a week before I need to connect to the grid or drive around. (Solar panels are, of course, an additional options, but when the new battery gives me enough power for a week, I think I would not need them.)

What I really can recommend is to adjust the bench and table of your van-office to your body size. I was lucky that my table was just the right height for me (73 cm). The rear bench, however, was too low. Fortunately, it only consists of a foam block on a kind of wooden box. To find the ideal height, I stacked some old computer magazines between the wooden box and the foam block and worked this way for some time until I was sure what the ideal height for the seat was. Then my brother, who is more skilled in woodworking than I am, made an additional wooden box of the required height, which we attached on top of the original box with wing screws so that it can be removed relatively easily if necessary.

I am using an encrypted hard-drive, just in case that my laptop gets stolen. And I regularly back up my work to an encrypted USB drive that I always carry on my keychain.