You know how to make your own BATTERIES? Wow. Got link?
It's a pretty common science project actually: just google "homemade battery" and you'll find hundreds of ways to do it. Basically, you need two different metals suspended in acid. I took copper from an old wire, some aluminum foil, and put them in some vinegar which also had salt in it. You can stick a piece of copper and a galvanized (zinc) nail into opposite ends of a lemon and that'll work. You can use bleach, salt water, cola, lots of things.
The current is very low, however. You have to connect a lot of them together to get a good current out of them--and you can probably only scrape together enough to run very low power devices. Still, once you know the scientific principle behind it, it's knowledge that may come in handy someday! :)
Here’s a neat link with lots of experimental charts and data:
http://www.hanssummers.com/radio/homebrew/battery/index.htm