We love building circuits around here. From our very first Circuit Bugs creation to Potato Batteries, we have had a lot of fun over the years experimenting with low voltage experiments and electricity in our elementary science lessons. With summer here, that means lemons and lemonade. It also means it was time for us to create the favourite lemon battery science experiment.
How to Build a Lemon Battery
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We often talk around here about the energy in nature and in everything around us. When we can power a light bulb with that energy it suddenly makes it very real for my kids. That energy isn’t just some crazy weird thing that I babble on about, it is this very real power that is showing itself right in front of them.
Normally our circuits are powered by batteries, but one day I convinced the kids we could power a light bulb with nothing but a potato. You should have seen the looks on their faces! Serious side eye was thrown my way.
Then, once they stopped straining their eyeballs, we built a potato battery and it worked! These kinds of science experiments for kids really stick with them. Why? Because it makes things real that they can’t otherwise see. Like the energy in our food.
Plus, when a child starts a science experiment with serious doubts, yet still achieves success, it powers up their curiosity!
So when we went grocery shopping and there was a huge pile of fresh, juicy looking lemons on display the kids asked to buy some for lemonade, but I knew we had another science experiment in our future.
Note: These food based battery experiments produce low voltage and are safe for older, responsible children to do under adult supervision.
How to Build a Lemon Battery Video
Watch as I go through the whole experiment step by step in our video tutorial. If you can’t see the video, please turn off your adblockers as they also block our video feed. Alternatively, you can also find this video on the STEAM Powered Family YouTube Channel.
Lemon Battery Materials
Lemons! You need at least 4 to create enough energy, but why not grab extras and experiment?
Copper anode strip plates
Zinc anode strip plates
Alligator clips with wires (2 per cell, so minimum 8 if you are creating a 4 cell battery)
LED light diodes
Knife and cutting board
Copper and Zinc plates are invaluable in our science experiments, but if you don’t have them, you can use copper pennies (the older the better) and zinc plated (aka galvanized) nails. Copper wire can also be used, and a search of your local hardware store is likely to produce other copper and zinc items you could test in your experiment.
Lemon Battery Science Experiment
The first step is to roll the lemons. Just like you would if you were about to eat or juice them. This releases the juices inside and we want our lemons as juicy as possible.
Start with one lemon and make a small cut through the peel on either end. It is very important that you place these far enough apart that the electrodes don’t touch.
Insert a copper plate on one side and a zinc plate on the other side.
Now using your multimeter test your energy levels.
We have energy!
Now it is time to start adding more cells (lemons) to our battery.
Repeat the above steps on a second lemon. Once you are finished use an alligator clip to connect the zinc plate on the first lemon to the copper plate on the second lemon.
Test your energy level with 2 cells (you will test by touching the copper plate on the first lemon and zinc on the second). Remember you are completing the circuit.
Now repeat the steps to add a third and fourth cell.
At 4 cells we are now registering more energy than 2 AA batteries, which we tested in our Potato Cell experiment.
Now it is time to hook up our light bulb!
The goal of making a lemon battery is to turn chemical energy into electrical energy, creating enough electricity to power a small LED light. You can also use limes, oranges, potatoes, pumpkins/squash, or other acidic foods.
How A Lemon Battery Works
How does a lemon battery work? The science behind how food can power a light bulb is really fascinating. Food has energy. With a lemon battery we are capturing that energy and using it to light up a LED. To do this we need electrodes to capture the energy from our electrolyte.
The zinc and copper plates are called electrodes, and the lemon juice is our electrolyte.
All batteries have a “+” (known as the cAll batteries have a “+” (known as the cathode) and a “-” (known as the anode) terminal. In our lemon battery, the copper plate is our positive cathode and the zinc plate the negative anode. The zinc metal (our negative anode) reacts with the acidic lemon juice (mostly from citric acid) to produce zinc ions (Zn2+) and electrons (2 e-).
Electric current is created by the flow of atomic particles called electrons. Conductors are materials that allow electrons (and the electrical current) to flow through them. Electrons flow from the negative to the positive terminal.
So in our experiment electrons are flowing from our zinc plate, through the lemon juice to the copper plate. From there it goes into our alligator clip, along the wire, into the zinc plate on the next lemon, where it picks up more energy as it travels through that cell. It continues on, building energy with each additional cell we add. Until finally we have enough voltage to power a light bulb.
Volts (or voltage) is a measurement of the force moving the electrons through our lemon battery. The higher the voltage the more power the battery has, but higher voltage also means greater danger. Always remember to be careful and safe around electricity. Thankfully our lemon battery is very low voltage.
There are a number of things that can cause issues with your Lemon Battery.
First, make sure none of your electrodes are touching anything other that lemon and alligator clips. Also, ensure your alligator clips are placed near the peel of the lemon.
Did you roll your lemons? You want them juicy for this experiment to work.
Did you mix up any of your connections? Remember you always want to link “+” to “-“. On an standard LED light bulb the longer pin is the positive connection.
Does your LED bulb work? Test it on a coin battery to ensure your bulb works. It may be you have a faulty bulb.
Another area that can cause problems is the quality of your copper and zinc. You want your copper and zinc to be as pure as possible so it can conduct the electrons without any interference. This is one of the reasons I suggest investing in proper plates, so you know the quality of your materials when conducting experiments.
Finally, these food based batteries dimly light up the LED. If you hook your LED up to a regular battery, it will glow much brighter.
More Fruit Battery Experiments
So now we have made both a lemon battery and a potato battery, which one is better? Both were able to light up our LED light bulbs, so in that sense they are both successful. However, the potato battery was definitely a lot more work. So if you are looking for a quicker experiment, the lemon battery is faster and easier. However, both have significant opportunities for learning and would make great science fair projects. Why not do both yourself and see what you think?
And in the fall, don’t forget to make a battery with pumpkins and squash! The concept is similar to Lemon Batteries but with a Autumn/Halloween theme.
Want to dig in more? Try this experiment with other citrus fruit such as oranges or lime or grapefruit. You can also combine a variety of fruits to see which combination makes the best fruit battery.
How to Reuse Lemon Battery Cells
This lemon science project is a ton of fun but once you are done, what can you do with the lemons? It seems like such a waste to throw them out. We have two really cool projects to do next with your lemons!
Check out the gorgeous lemon volcano we created here after building our lemon batteries!
Another great project with these lemons is to make Lemon Oobleck for a fun, summery sensory project.