The Superpositioned site has an interesting article about making a battery out of some pennies, an ice cube tray and a few paper clips. The battery is shown powering an LED.
“In order to turn pennies into batteries, another electrode and an electrolyte are needed. In this case, dimes (zinc) are used as the positive electrodes and salt water is used an electrolyte. Copper wire, galvanized nails, and lemon juice are also popular and cheaper solutions. Such a battery produces a differential of about 0.5 volts.”
via Digg
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yup, not so cost efficient.
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wat the heck