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Picture of Potato Battery Driven LED
So, if you looked at my profile you would see that I like physics.  When the challenge for “Potatoes” I just knew that I need to do a project that highlighted the lowly “Potato Battery”.  So here is how to make a Potato Battery and have it light an LED light.
 
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Step 1:

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Supplies:
Potatoes
Galvanized nails
Shinny copper pennies
Wires with alligator clips on each end (2+ per battery)
LED bulb
Multi meter
Knife
Cutting board

Step 2:

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PotBat 17.JPG
A battery is a way to store electrical energy.  For a battery to work it needs to have 3 things, two electrodes (metals, one + and one -) and electrolytes (minerals).  The batteries we are going to make today uses the electrodes of copper (pennies, anodes, +) and zinc (galvanized nails, cathode, -) and the electrolyte of K (Potassium) that is found in potatoes.

Step 3:

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Take a potato

Step 4:

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and cut it in half. This will make 2 batteries. Potatoes are juicy, which is part of the reason they can be made into batteries.

Step 5:

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Take a knife and put a slit in the potato and slip the penny into the slit. Push as much of the penny into the slit as possible, you want just a little bit sticking out of the potato. Push the nail most of the way into the potato,(at this point I cut the nails in half, so that they weren't so tall). Do not let the electrodes touch, keeping them about 1 inch apart.

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Turn on the Multimeter and put it at the lowest voltage reading. Make sure the red probe is in the + slot and the black probe is in the – slot.

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Use the red line to touch the penny in the potato and the black line to touch the nail. You can read how much voltage you have available in this potato battery. It reads .85 volts, not bad but not enough to do anything fun.

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To increase the voltage, you will need to create more potato batteries and wire them in a series (that means to connect the + electrode of one battery to the – electrode of the next battery). So I created 3 more batteries from 3 more potato halves.

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Then I used the alligator clips connected to wires and wired first 2 potatoes together,

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this time the voltage read 1.69 volts.

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Let's take a minute and look at the LED light. It has one long leg and one shorter leg. The longer leg is the anode (+) and the shorter leg is the cathode (-). I clipped the batteries to the LED light (+ to+ and - to-), no light, therefore, not enough voltage.

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I wired all four batteries together in series, and found what the total voltage is of the 4 batteries was 2.38 volts and I again wired in the LED light, again no light.

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Finally I wired six batteries in series and it had a 4.05volt reading.

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This time the light lit up!  Hurray!   Potatoes can be used as batteries.

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Have fun playing with your new batteries, maybe you would like to experiment with increasing current by wiring the potato batteries in parallel as well as series.  Good luck and Enjoy!
MacjucomK6 months ago

trying to do this in my science Investigatory Project may I ask if how many is the required voltage for the bulb your using because i tried it with a 12 volt bulb and it took me like 10 potatoes and still no light

craftknowitall (author)  MacjucomK6 months ago

One potato battery will make about 0.85 volts. Do the Math to determine how many batteries you will need to light a 12 volt light. Maybe you will need to switch to a lower voltage LED light. Mine only needed 6 batteries to get mine to light. Hope this helps and thanks for asking.

RajeshS37 months ago

Good info. I sure am going to try it. Probably have my kid take it to school as a project.

Thanks mate..

craftknowitall (author)  RajeshS37 months ago

Welcome. I used it as a project in a class with teenagers. I thought it was fun! Thanks for commenting.

D5quar32 years ago
If the battery works on the electrolyte Potassium, is it possible to make this work with salt water? Would NaCl be electrolytic enough?
yes you can
craftknowitall (author) 2 years ago
Yes it can. Look at this Instructable to learn more: http://www.instructables.com/id/Salt-Water-Powered-Paper-Lights/.  Thanks for commenting.
MakingWorld3 years ago
science comes from the life.
Are your potatos rechargeable:)
scoochmaroo3 years ago
Woman, you never cease to amaze me!
craftknowitall (author)  scoochmaroo3 years ago
I keep coming back to this comment, it really tickles my fancy. :)
craftknowitall (author)  scoochmaroo3 years ago
When I first learned that the Challenge was potatoes, I knew that I will have to do something wild and wonderful, which meant, not my "potato soup or salad" recipes. Glad you like it.