The penny battery is a voltaic pile which uses various coinage as the metal disks of a traditional voltaic pile. The coins are stacked with pieces of electrolyte soaked paper in between (see diagram at right). The penny battery experiment is often during electrochemistry units in an educational setting.
Each cell in a penny battery can produce up to 0.8 volts, and many can be stacked together to produce higher voltages. Since the battery is a wet cell, the effectiveness will be reduced when the electrolyte evaporates.
As the name implies, Canadian pennies from 1997-1999 may serve the zinc electrode and 1942-1996 pennies as the copper. Alternatively, American pennies from 1982-present may be used as the zinc electrodes and 1944-1982 pennies as the copper electrodes. A variety of other coins may also be used, with varying results. [1][2]