thumb|right|Diagram showing three lemon cells wired together so that they energize the red light-emitting diode (LED) at the top. Each individual lemon has a zinc electrode and a copper electrode inserted into it; the zinc is colored gray in the diagram. The slender lines drawn between the electrodes and the LED represent the wires.|alt=A drawing showing three lemons and a glowing red object (the LED). The LED has two lines coming out of its bottom to represent its electrical leads. Each lemon has two metal pieces stuck into it; the metals are colored differently. There are thin black lines, representing wires, connecting the metal pieces stuck into each lemon and the leads of the LED.

A lemon battery is a simple battery often made for the purpose of education. Typically, a piece of zinc metal (such as a galvanized nail) and a piece of copper (such as a penny) are inserted into a lemon and connected by wires. Power generated by reaction of the metals is used to power a small device such as a light-emitting diode (LED).

The lemon battery is similar to the first electrical battery invented in 1800 by Alessandro Volta, who used brine (salt water) instead of lemon juice. Potato batteries with LED lighting have been proposed for use in poor countries or by off-grid populations. International research begun in 2010 showed that boiling potatoes for eight minutes improves their electrical output, as does placing slices of potatoes between multiple copper and zinc plates. Boiled and chopped plantain pith (stem) is also suitable, according to Sri Lankan researchers.

Instead of fruit, liquids in various containers can be used. Household vinegar (containing acetic acid) works well.

Zinc and copper electrodes are reasonably safe and easy to obtain. Other metals such as lead, iron, magnesium, etc., can be studied as well; they yield different voltages than the zinc/copper pair. In particular, magnesium/copper electrodes can generate voltages as large as 1.6 V in lemon cells. This voltage is larger than obtainable using zinc/copper cells. It is comparable to that of standard household batteries (1.5 V), which is useful in powering devices with a single cell instead of using cells in series. With the imperfectly refined zinc in 19th century laboratories they typically gave different voltages.

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Further reading

  • Description of an acid cell with zinc & copper electrodes, including a JAVA-based animation. The animation shows zinc dissolving into the electrolyte, electrons flowing from the zinc to the copper electrodes, and little hydrogen bubbles coming off the copper electrode. The animation also suggests that a single cell can light an LED, which is not possible for LEDs that emit visible light.
  • <!--The reference is included here because of the popularity of the television program.--> Online preview only.
  • Lemon Battery video. Cool and fun animated video explaining in great detail how a lemon battery works from the inside.
  • Orange battery video. The orange battery powers an inexpensive digital watch.
  • . Three potato cells in series power a calculator.