# How to Make Batteries From Spare Change

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## Step 1: See the Video!

What's a penny worth these days?  Not much, but could there be some free energy hidden inside your spare pennies? You'd be surprised! Watch the video to learn how you can put together stacks of pennies to form makeshift batteries that can drive small-current devices like LEDs and calculators.

## Step 2: What Kind of Pennies?

US pennies that are newer than 1982 will work for both of these experiments, because they're nearly 98% zinc.

## Step 3: Power a Calculator With 3 Pennies!

Here's a fun experiment!

Pick up a calculator from the dollar store and remove the screws on the back so you can get to the battery. Remove it, and save it for another project.

Now pull the negative and positive leads out of the casing and attach wires to the terminals if you can.  I just twisted the wires to the battery leads, and used electrical tape to hold them together.

Now it's time to make the penny battery.

I found the easiest way to make one is to combine the pennies with some zinc washers from the hardware store.  A pack of 30 is about \$1.

Get some cardboard, and cut circular pieces so that the edges are just bigger than the pennies.  Let them soak in white vinegar for about 1 - 2 minutes.

Note: Any kind of vinegar should work, and if you don't have vinegar, try salt water, or lemon juice.  They will all work just fine.

Start your battery cell by placing a piece of aluminum foil on your workspace, and place 1 zinc washer at the end.  Next, take a piece of cardboard, soaked in vinegar, blot dry it on some paper towel, and place it on top of the washer.  Lastly, place the copper penny on top of the cardboard, and the battery is done!

An individual battery cell is a zinc bottom, copper top, and separated by a material like paper or cardboard that's been soaked in an electrolyte.

From my testing, each cell yields just over 0.6 volts, and around 700mA.  The copper top is positive, and the zinc bottom is negative.  This calculator needs around 1.5 volts, so I used 3 pennies, 3 washers, and 3 pieces of cardboard soaked in white vinegar.  (3 cells x 0.6 volts = 1.8 volts approximately)

I added wires to the top and bottom for ease of use, then used some electrical tape to hold it together.  The aluminum foil is no longer needed.

This type of battery cell is pretty much the same as the first one ever invented by Alessandro Volta in the early 1800's, which came to be known as the "voltaic pile".

## Step 4: It Works!

The wires can now be connected to the correct battery leads that were pulled out earlier, and when you press the "on" button the calculator will fire right up!

I tested out a few functions and everything calculated correctly.

It's amazing to think you can run low current electrical devices on this penny power hack!  It works great, and as long as the cardboard is moist with electrolyte, it should work.

If your battery stops working, try re-soaking the cardboard in a little more vinegar to get it wet, then try again.  It should fire right back up!

## Step 5: Making a Larger Wet-Cell Battery

Here's another way to make the battery if you don't have access to zinc washers;

Pick out 10 pennies newer than 1982, and use 100-grit sandpaper to sand one face of the penny.  The entire inside of the penny is zinc, so sand the face until the whole surface exposes the zinc.

Once again, cardboard needs to be cut and soaked in an electrolyte like vinegar, salt water, or lemon juice.  In this case, I didn't round the edges.  You can see the sharp corners, and that's ok as long as they don't touch.  If the cardboard pieces touch, that section of the battery will short out and decrease the performance of the unit as a whole.

You can build your battery cells the same way you did with the washers, as long as the pennies are all facing the same direction.  With this method, the zinc top is the positive, and the copper bottom is negative.

By connecting 10 cells in series (stacking them on top of each other), the electrical potential will jump to nearly 6 volts!  This should be more than enough voltage to drive an LED… or TWO?!?

You can get an LED to light up by pressing the long lead of the LED (positive) on the top, and the short lead of the LED (negative) on the aluminum foil base.

LEGALITIES: Some people have asked about the legality of treating pennies in this manner.  The federal law states that there are exceptions made for use as "educational, amusement, novelty, jewelry, and similar purposes as long as the volumes treated and the nature of the treatment make it clear that such treatment is not intended as a means by which to profit solely from the value of the metal content of the coins." For more information, click here!

## Step 6: How Long Does an LED Stay On?

With the stack of 10 pennies, I attached a green LED and wrapped it all up with electrical tape in hopes to make it air-tight.

I set it on my shelf and watched it for a few hours to see when it would die out.

I was amazed that the light actually stayed lit for over 16 days!!  I really am impressed at how well that worked out!

Well, there's an energy idea that's worth a few cents.

Haven't see the video yet? You can still see it here!

If you like this project perhaps you'll like some of my others. Check them out at www.thekingofrandom.com

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## Questions

Hi,

This did not work for me. I followed the instructions exactly as given.

is it rechargable

I imagine you just add more vinegar to the cardboard. I am going to have to try this.

Are these batteries rechargeable?

Well, here in Canada the Royal Canadian Mint stopped producing pennies a couple of years ago. Now we can't build penny batteries.............

Nice science demo instructable.

2 replies

Do you know if Canadian pennies would've worked for this? Cause I've still got a jar of them that I was wondering what to do with...

this is really cool I also really enjoyed your five ways to start a fire

I wonder if I put together 3 parallel stacks of 6 pennies if I could use that as an emergency cell phone power source.

2 replies

a green LED works at as low as 2.1V, you'd need at least two of these in series, probably more around 3 to get the necessary 5V, also, that LED takes around 20mA, compared to a phone that should take much, much more. With enough batteries, it should be possible tho

Fascinating!

Great Instructable! Love your channel too.

Had a question on the assembly. You say to start by placing aluminum foil on your worskspace. After you build your cell, do you wrap the foil around it and the nadd the tape? Or do you wrap it without the foil?

Thanks, and keep up the great work!

i doubt it, that would make a contact in between the top and bottom, which is actually a short, so all the power (as small as it is) will go through that instead of whatever you want to power

nice instructable. I have not seen any where a crediting of this device to it's discoverer. It is a Voltaic pile discovered / invented by Alessandro Volta in the 1880's.

Faraday did many experiments on it. He used salt water as the electrolyte.

I have been meaning to make one myself and this is great encouragment

uncle frogy

I'm from the Philippines and I would like to try this out as our Investigatory Project in Science, but so far I haven't made it work yet. Any advice? I use our copper coins, some cardboard and washers.. I'll give you full credit for the idea!

2 replies

Maybe you should look up basic physics to fully understand what's this is about. But in basic you need copper and zinc, your stack probably don't work because your washers don't have zinc on them.

Either that, or your coins are actually copper. Since the early 80's, American 1¢ pennies are 95% zinc.

wow,neat. Could you put this in a tube.....maybe a glass cigar tube and make it almost mobile. thanks again

Awesome!!! Well done

This will certainly be helpful :)