How to Make a Fruit Battery

Use fruit to generate electricity for a light bulb

Making electricity with citrus fruit

Tim Oram / Getty Images

If you have a piece of fruit, a couple of nails, and some wire, then you can generate enough electricity to turn on a light bulb. Making a fruit battery is fun, safe, and easy.

What You Need

To make the battery you will need:

  • Citrus fruit (e.g., lemon, lime, orange, grapefruit)
  • Copper nail, screw, or wire (about 2 in. or 5 cm long)
  • Zinc nail or screw or galvanized nail (about 2 in. or 5 cm long)
  • Small holiday light with 2 in. or 5 cm leads (enough wire to connect it to the nails)

Make a Fruit Battery

Here's how to make the battery:

  1. Set the fruit on a table and gently roll it around to soften it up. You want the juice to be flowing inside the fruit without breaking its skin. Alternatively, you can squeeze the fruit with your hands.
  2. Insert the zinc and copper nails into the fruit so that they are about 2 inches (5 centimeters) apart. Don't let them touch each other. Avoid puncturing through the end of the fruit.
  3. Remove enough insulation from the leads of the light (about 1 in. or 2.5 cm) so that you can wrap one lead around the zinc nail and the other lead around the copper nail. You can use electrical tape or alligator clips to keep the wire from falling off the nails.
  4. When you connect the second nail, the light will turn on.

How a Lemon Battery Works

Here are the science and chemical reactions regarding a lemon battery (you can try making batteries from other fruits and from vegetables):

  • The copper and zinc metals act as positive and negative battery terminals (cathodes and anodes).
  • The zinc metal reacts with the acidic lemon juice (mostly from citric acid) to produce zinc ions (Zn2+) and electrons (2 e-). The zinc ions go into solution in the lemon juice while the electrons remain on the metal.
  • The wires of the small light bulb are electrical conductors. When they are used to connect the copper and zinc, the electrons that have built upon the zinc flow into the wire. The flow of electrons is current or electricity. It's what powers small electronics or lights a light bulb.
  • Eventually, the electrons make it to the copper. If the electrons didn't go any farther, they'd eventually build up so that there wouldn't be a potential difference between the zinc and the copper. If this happened, the flow of electricity would stop. However, that won't happen because the copper is in contact with the lemon.
  • The electrons accumulating on the copper terminal react with hydrogen ions (H+) floating free in the acidic juice to form hydrogen atoms. The hydrogen atoms bond to each other to form hydrogen gas.

More Science

Here are additional opportunities for research:

  • Citrus fruits are acidic, which helps their juices to conduct electricity. What other fruits and vegetables might you try that would work as batteries?
  • If you have a multimeter, you can measure the current produced by the battery. Compare the effectiveness of different types of fruit. See what happens as you change the distance between the nails.
  • Do acidic fruits always work better? Measure the pH (acidity) of the fruit juice and compare that with the current through the wires or brightness of the light bulb.
  • Compare the electricity generated by fruit with that of juices. Liquids you can test include orange juice, lemonade, and pickle brine.