Frequently-Asked Questions
about food batteries

Where can I find copper?

Copper can be found at any good hardware store, in spools. Copper wire is easy to come by. I suggest you buy short pieces of heavy, solid wire such as that used for major electrical hookups in your home; it can be beaten flat with a hammer to give more surface area. (Strip off the insulation first--and I am sorry if I sound insulting. The "obvious" isn't always obvious.) You can also order copper strips from a chemical supply house (see the next answer).

Where can I find zinc?

Zinc can easily be obtained from a chemical supplier (try www.sigmaaldrich.com or www.alfa.com). But you might try a galvanized nail or screw (what is "galvanized"?) Try to get the really bright silvery ones; they'll have more zinc on them, I think. We ran some tests using a galvanized screw as the zinc electrode and a piece of heavy copper wire as the copper electrode, and got satisfactory results.

Experimental work performed by Jerrad Businger and Grace Faruk.

Why doesn't my light bulb light?

You may get good voltage (typically ½ to ¾ volt) from a single food battery, but you are not likely to get much amperage.

When we measured the current from a single lemon cell (electrodes: galvanized screw and heavy copper wire), we got less than 20 microamperes, that's less than 20 one-millionths of an ampere. (20 μA is the lower limit of our multimeter.)

Get a multimeter (from Radio Shack or an electronics repair store) and measure the volts and amps coming from your food battery. The folks at Radio Shack should be able to help you learn to use the thing.

Light bulbs not only require substantial voltage (typically 1.5V to 3V for flashlight bulbs) but substantial amperage.

Look it up. How do light bulbs produce light? Why do they get so hot that a 100-watt light bulb is the heat source for the Easy-Bake Oven?

So a light bulb is NOT likely to work with a single fruit battery, despite what I said in my Mad Scientist answer.

See also the Lemon Power Project from EnergyQuest.
See also Dr Dan's Lemon Power Website. Warning: Dr. Dan gives results using magnesium metal. Magnesium is inflammable, it burns hot enough to cause severe damage to anything you set it on, and you cannot put it out with water.

What else can I use that will light up?

Try a light-emitting diode (LED). You can get them at any electronics supply store, like Radio Shack.

Caution:

1. LEDs are one-way devices. They only work if they are placed in the circuit correctly. Worse, they burn out if placed in the circuit backwards. So get a dozen or so. Then learn which way is which!
2. LEDs require a certain minimum voltage. So make sure that you have it before deciding the LEDs don't work.
3. LEDs burn out at ridiculously low current levels (amperage). Check the volt/amp rating on your LEDs, and be prepared to use resistors to reduce the current if necessary. You can get resistors at the same place you got the LEDs.

Why can't I just use fruit juice? Isn't that the same as a bunch of pieces of fruit?

Remember that one food battery equals one pair of electrodes plus one piece of fruit or whatever. Don't expect that if you put five pieces of fruit in a blender, then stick in two electrodes, you'll get any more electricity than from one piece of fruit.

1. Things to look up in a textbook. Why do you need two different metals? Where do the electrons come from, and where do they go? Which electrode is positive, and which is negative?
2. Things to think about. If what you found is true, why do you need the piece of fruit? What else might work?

Click me for instructions Experimental work performed by Jerrad Businger and Grace Faruk.

So how do I get enough juice to light up that darned bulb, anyhow?

To get more voltage, put batteries in series: plus to minus. To get more amperage, put batteries in parallel: plus to plus and minus to minus. This can all be found in textbooks on electricity and electrical experiments, in your library. You may need to experiment a bit before finding a combination that works. Use the multimeter to determine how much current and voltage you are getting with each setup you try.

For a light bulb you need more than an ampere--even LEDs require several milliamperes--and a food battery puts out current in the microampere range--so you'd need a million of 'em, literally, to light a bulb directly. However, you can charge a capacitor with a lemon cell--and eventually you'll have enough juice stored in the capacitor to light up an LED or even a light bulb. A circuit diagram that uses capacitors to light an LED is shown at right. Remember that both LEDs and capacitors are one-way devices and only work when hooked up in the proper direction!

Another suggestion (from Purdue University) to get more power from your lemon:

1. Connect a zinc and a copper electrode with a jumper cable.
2. Place the copper electrode near your first zinc electrode, and the zinc electrode near your first copper electrode. This increases your power by lowering the internal resistance of the cell.
3. Repeat (carefully) as needed, testing for voltage and amperage each time.

Remember, experimental work is full of setbacks. Don't be discouraged.

See also the Lemon Power Project from EnergyQuest.

See also Dr Dan's Lemon Power Website Warning: Dr. Dan gives results using magnesium metal. Magnesium is inflammable, it burns hot enough to cause severe damage to anything you set it on, and you cannot put it out with water.

See also this demonstration (from Purdue University) of a lemon-powered digital clock. Something like this can be purchased from Edmund Scientific (search for "potato clock" or "water clock")

Maintained by Dan Berger.

This page has been translated into Belorussian by Amanda Lynn
This page has been translated into German by Alexey Gnatuk of LED-Leisten