Are you looking for a simple science fair project for tweens or a science experiment with electricity?
This Lemon Battery STEM activity would be perfect to do in the classroom, at a scout meeting, or at home. Use it in conjunction with a lesson on electricity, or do it as a stand alone activity.
If you are looking for more fun ways to keep kids busy and engaged, be sure to check out our other STEM activities for kids.
Making a fruit battery is a fun science experiment for tweens and teens to do.
Younger kids will have fun helping or watching what happens once you complete the circuit.
Take the learning further with this graphite circuit activity.
Lemon Battery STEM Activity
Materials Needed:
- 6 Lemons
- 6 Shiny Pennies
- Soapy Water
- Sharp Knife
- 6 Zinc Galvanized Nails
- 7 Alligator Clip Battery Leads
- Mini 5 mm LED Bulb
Depending on their size, you may be able to make your battery using just 4 of your lemons. We had fairly small lemons, and wound up needing all 6. If you want, you can start with just 4 and add more as needed.
Start by rolling and squishing your lemons a bit to get their juices flowing. This is an important step as the acid in the juice is necessary to make your battery strong enough to light the LED bulb.
Then use your knife to make a ½-inch-long slit in each of your lemons. Make sure the slit goes all the way through the lemon’s rind.
Wash your pennies in the soapy water to remove any dirt. Dry them thoroughly.
Slide a penny into the slit of each lemon. Be sure your pennies go in far enough to touch the lemon’s juicy insides.
Next, push a nail into each lemon so only a small portion of the nail sticks out. The nail should be about 1 inch away from your penny. You do not want your nail and penny to touch.
Arrange your lemons in a circle. This will make it easier to connect them together.
Now you will need your alligator clips. You can find these at a local car parts store or online.
Clip one alligator clip to the penny in your first lemon. Fasten the other end of the lead to the nail in the next lemon. 
Continue connecting the clips in this manner until you get to the last lemon.
On your last lemon connect a clip from one alligator lead to the penny, but do not connect it to the next nail. Instead you will use your last lead to hook onto the remaining nail.
You should now have 2 clips not connected to anything.
Attach these 2 remaining clips to the wires on your LED bulb.
Look carefully at your LED bulb. There should be one wire that is slightly longer. The clip connected to the penny should clip to the longest wire of the bulb. (This is the bulb’s positive side.)
Your bulb should light up. 
If your bulb doesn’t light up, try unhooking it and turning it to clip the leads onto the opposite wires of the bulb.
If it still doesn’t light up, check all your connections. Make sure the clips are secure and the pennies and nails are far enough into the lemons and that they do not touch.
If it still doesn’t work and you opted to try 4 lemons first, try adding another lemon.
How a Lemon Battery Works
In order for a battery to work, you have to have 2 electrodes, separated by an electrolyte.
In your battery, the lemon juice is the electrolyte and the zinc nail and copper penny are acting as the electrodes.
Chemical reactions occur inside the lemon where the electrodes touch the juice. These reactions produce electricity as soon as you complete the circuit and a path is made with your leads from one electrode to the other.
Each lemon is one cell of your battery. So if you use 4 lemons, you have a 4-cell battery. If you use 6 lemons, it is a 6-cell battery.
Extension Activities for Lemon Battery Experiment
- Make a hypothesis. Can other fruits or vegetables to produce electricity? Test out your hypothesis and try it with oranges, apples, or potatoes.
- How will using other metals affect your battery? Try using other metals as your electrodes. Instead of pennies try nickels or quarters. Use different types of nails instead of the zinc ones.
- Can your battery light up more than one LED bulb? Give it a try!
- Now that you know how a battery works, use one to make an electromagnet.
This Lemon Battery STEM activity is a fun way for kids to learn about circuits and electricity.
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