I've been looking at different portable power options. It started when I bought a tablet computer, and wondered how to keep it charged when the power goes out. Then, I needed to move some water out of the basement. I used a 12V bilge pump with two 6V lantern batteries connected together.
https://www.backwoodshome.com/category/energy/ has a few articles.
https://www.backwoodshome.com/power-up-bag/
https://www.backwoodshome.com/job-site-solar-power/
https://www.backwoodshome.com/keep-those-gadgets-working-after-the-power-goes-out/
https://www.backwoodshome.com/solar-suitcase/
https://www.backwoodshome.com/build-a-community-assistance-recharging-station/
I had to fill up some 5 gallon buckets, so I got the bilge pump out again, and used my small 12V battery in an ammo box for power.