Build your own penny battery: Materials & steps

- [Voiceover] In order to make a penny battery, you'll need five U.S. pennies, four of which were made after 1982. So look on the side that has Lincoln's head and check out the date. You'll also need a piece of sandpaper. This is 100 grit sandpaper, you can get it at a hardware store. You need a red LED, which you can buy at an electronics store. Super Bright ones are the easiest to see. Four small squares of mat board or any other absorbent material like cardboard would work as well. You need some water in a small container. Into that water you should add a bunch of salt and a little bit of vinegar, both of which you could get at a grocery store. You might also like to have some electrical tape, and anytime you have water you'd be happy to have some paper towels in case you have an accident. The basic building block of a battery is having two different metals in a salty solution in between. You're going to make a salt solution by taking your small container of water and adding salt until you have a saturated solution. That means you're going to add enough salt so that you might still see some solid salt particles that haven't dissolved, that's just fine. Then this battery works a little better if the salt solution is acidic, so take your vinegar and just add a little bit, the amount really doesn't matter. We're going to use the mat board squares to soak up the salt solution. So I've cut four pieces of mat board that are about the size of a penny, and just stick them in the solution so that they soak up all that salt water. The two different kinds of metal are going to come from pennies made after 1982. Before 1982, pennies were mostly copper, and after 1982 the mint changed the recipe so that the centers were made of zinc. There was only a copper coating on the outside. We're gonna expose that zinc center by sanding off one face of the penny. A little tip is that the Lincoln Memorial side, the tailside of the penny, is easier to sand off. So I like to take my sandpaper, put my penny with the Lincoln Memorial side down, and then just sand off as much as I can. After a little bit of sanding, you'll see that the zinc side of the penny is starting to show through. But there's still quite a bit of copper, so we need to keep sanding until the entire face of the penny is zinc. Eventually, you'll see that you've sanded off the entire copper surface of the penny. The whole face is this shiny silvery zinc color. So go ahead and and do that with the other three pennies that were made after 1982. Once you have that fourth penny sanded, you'll have four pennies that have zinc on one side, copper on the other and then that fifth intact penny, and you'll be ready to start building your cell. Go ahead and take the four mat board squares and dry them off on your paper towel. We're going to start building the individual cells that we'll combine in series to create your battery. So we're gonna assemble each cell of this battery and then combine the cells to make the complete battery. You're gonna do that by taking the sanded penny with the zinc side up and placing a salty mat board on top. Then you'll repeat it with the three other sanded pennies. We're gonna start assembling this battery by taking one cell that is zinc, salt and the copper that's on the bottom of the next penny, as my first cell. This is actually one and a half cells because I have another surface of zinc and salt ready for my next penny. I'm gonna keep going until I have my fourth mat board right on top. So I have zinc, salt and it's ready for copper side. That's where that fifth penny comes in because both sides are copper. So you can just put that whichever way you want, either side on top. Now I have a four cell battery... That is made of alternating layers of zinc, salt and copper. To see if your battery works, you wanna try to power something, and that's where your LED comes in. LEDs only work in one direction, so this is important. Take a look at your LED and see which leg is slightly longer. The slightly longer leg is the positive terminal, and that's the side that's going to go to your intact copper penny. So I'm gonna bend my LED so the short leg goes through the bottom and the top leg goes through the top. You can see that the red LED starts to light. So this five penny battery is enough to power a red LED. At this point, to make it easier, you can take a small piece of electrical tape and wrap the whole battery together... So that you have a little flashlight.