Nice to know. :)

Reading tip: a comment from a reader John Beech (an old radio amateur) at the bottom is probably of greater practical value: he describes how he developed DIY cells to the point of running a 2 W radio.

Another way to build DIY batteries is using the iron-air chemical combination. A decent collection of recipes can be found here, using filter cartridges of activated carbon as cathodes and rebar wrapped in steel wool as anodes:

https://www.instructables.com/Create-large-refuelable-metal-air-battery/

These cells convert iron into rust at an accelerated pace, producing power while doing that. However, they have really low cell voltages, so you have to wire many cells in series or use a really efficient voltage converter. Aluminum gives high cell voltages, but on the downside, produces annoying waste chemicals.