[Christ]

Country areas around you? Do you mind reviving dead batteries?

Salvage batteries can normally be had from any tractor supply company (farm equipment), since they usually pay people up to $3 each for scrap batteries (undrained).

Let them know what you're doing, and they may be willing to help out.

Junkyards are typically a good place to get halfway decent batteries as well, and if nothing else, you could even start off with a small battery from a power-wheels toy or something, whatever you can make provide 12V.

You might find some rechargeable 6V flash light dry-cells relatively cheap too. The lantern batteries, I mean. (You can actually start a car on two new ones, wired in series.)