Introduction: How to Make Batteries From Spare Change

About: Random Weekend Projects

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.

For more information on US pennies, including what date ranges contained what ratios of copper and zinc, click here!

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
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