Calculators, LEDs, and other low-power devices can be run from a very basic battery constructed from a few pennies, zinc washers, and small cardboard circles soaked in vinegar.


Instructables user The King of Random builds this basic battery by stacking washers, vinegar-soaked cardboard cutouts, and 1983 or newer pennies sanded down on one side to remove the copper plating and reveal the zinc core. Stacked in a series, these should store enough electricity to run a small cheap calculator, LED lights, or other device with low power requirements.

If you're worried about defacing pennies (which can sometimes be illegal) but the Federal Register dictates that "the regulation includes an exception for the treatment of 5-cent and one-cent coins for educational, amusement, novelty, jewelry, and similar purposes as long as the volumes treated and the nature of the treatment make it clear that such treatment is not intended as a means by which to profit solely from the value of the metal content of the coins."


How to Make Batteries From Spare Change | Instructables