Q & A: Why won’t my lemon battery work?

My daughter and I are doing the lemon battery experiment for a science prodject and are currently having trouble making it work.We have hooked up as many as nine lemons together both in series and paralell and every combination in between and still can’t make the experiment work. Here’s what we did:using copper wire(14 guage)and both paper clips and zinc coated screws as electrodes we inserted them two centimeters apart in each lemon.Hooking the lemons together we were able to get 3.6volts on a voltometer.We purchased a number of items from "Radio Shack"whick ranged from lights(1.5v,2.0v,2.5v)small dc motor(2.5v)and a buzzer(3.0v).None of the items would work.We tried adding three sets of three lemon cells together thinking this would provivide more current.We got a reading of 1.8v on the voltometer but still could not get any of the items to work,not even the 1.5v light.We connected the electrodes together with wire connectors(alligator clip at each end,store bought).Could you please tell me what we are doing wrong.What else could we use for electrodes? What are common items that are made from zinc or magnesium that could be used?Please reply A.S.A.P. as the prodject is due very soon.
- John Kendrick
Edmonton,AB,Canada

John -

In order power a lightbulb, it needs to be provided with both voltage and current. As you've already checked the voltage across the lemons by using a voltmeter, you know that your setup is correct. The important thing now is that you need to get more current. (You may recall that power = voltage * current, so you'll need to increase the current in order to get enough Watts of power to light the bulb.)

You've got the right idea by using cells of lemon batteries together. By connecting more of these cells in parallel, you can increase the current. (By using more lemons in series in each cell, you can increase the voltage.) In order to check how much current you're getting, you'll need to use an ammeter. Your voltmeter probably has a setting which measures milliamps, and this will work for measuring current as well.

If it turns out that you're not getting enough current then you'll probably need to use even more lemons. The only other thing that may help beyond that is if you squish the lemons first so that they're really juicy inside. This might help to increase the current that you get from each one.

If the ammeter shows that you are getting enough current to run your lightbulb, then the problem is most likely to be in the lightbulb, not the battery. Make sure that you're attaching the wires to the lightbulb correctly, and check that the bulb isn't dead using a regular battery. If the lightbulb still won't work, you should be able to power a small digital watch using several lemons.

If you still can't get it to work, some other experiments along the same line of thought include touching your tongue to a wire attached to only one lemon battery. Because the lemon produces such a small current, this won't hurt you, but you should be able to feel a tingle. Also, you should be able to hear a crackle inside the lemon if you put your ear up to it. (I've never actually tried this myself, but I've heard that it does work.)

Beyond that, I really don't know what to say. Good luck!

-Tamara

(published on 10/22/2007)

I also did this experiment but with potatos too. i found the potatos did not produce enough amperage(DCma). i connected to a AA battery to see the difference and the batteries amperage was off the scale as where the potatos was very small. Although if you did want enough amperage, larger citrus fruits help and more fruit can increase it enough to power a light bulb
- river (age 16)
new mexico

Thanks.

Mike W.

(published on 01/26/09)