When I was on holiday recently I read the book "Electrified Sheep" which amused me. But it mentioned the voltaic pile - an early kind of battery. So I decided that I should build one :-) I used some US coinage that was sitting in a drawer. I cleaned the coins by soaking them in coca-cola. Then dissolved some dishwasher salt in warm water to act as the electrolyte. I soaked small bits of kitchen towel in that solution and put them between the coins, like this:
To my amusement, this was enough to light a suitable LED. This is what I got on the voltmeter:
...somewhere around 2 volts. I'm wondering what I could run off it, umm ... interesting.