A little crank that makes things bright?
Are we not all familiar with Slug Signorino already?
For when you don’t want to count on solar power:
One solution we found, on long shoots away from power, to the price of camera batteries was car jump booster packs. The ones that basically have a car battery in them and a 12v take-off. They are much cheaper than Camera specific batteries. Then you just need a power inverter to charge up the actual camer batteries. It only works if you a have a truck with you though, they are way to heavy to backpack in with.
Brilliant. In a similar vein, I always have a DC to AC inverter in the car. When driving between locations, we can run the battery charger and stay ahead of the game.