 Let's look at some batteries. First of all, batteries provide energy or they can be used to store energy. And what we have here are a variety of batteries that you're familiar with. We have a 12-volt car battery, a 12-volt battery for your motorcycle or lawnmower. We have one-and-a-half volts that you probably have in your calculator or something like that. We have nine volts. We have one-and-a-half volts of a variety of different sizes. So typically we call this a wet battery and these are dry batteries, but in reality they're all wet. You have to have a moist environment for the electrons to flow from one connector to another. If we look at our car battery, what you have is the potential using this standard reduction potential of only two to similar metals or solutions. You're only going to be able to get about two to three max per cell. So in order to get 12 volts to run our cars, we have to have a series of cells. So you can see there's one, two, three, four, five, six separate cells. Each one of these cells will produce about two volts. So two times six is 12. That's what gives us our 12-volt battery. And if you look closely inside here, you can see it is a whole series of grids. So here you can see that we have a grid and you have lead oxide deposited on that grid. You have a separator. We don't have it here, but you can see where the separator goes between the grid. And then you have another grid in which where the lead is deposited. So having the grids, the electrons can be added to the lead ion and plated back. So when you're recharging the battery, you're forcing the lead to be redeposited. And so you want to have a lot of surface area and these grids in order to do that. So these are rechargeable. So what happens in your car is as you're using your battery to play the radio, for example, the lead and the sulfuric acid inside are producing an electrical current. And so the lead is going from lead to lead oxide. Then at the same time as your car is running, your alternator is taking that energy and running the reaction in reverse, taking the lead oxide and replacing the lead. So that's how you can have a rechargeable battery is you're forcing the electrons in one direction. When you're using it, they're going in the opposite direction. And your electronic devices, your toys, they're actually a wet device. But so you don't want to slush around like you would in this battery. It's actually just a paste. So you can see this black pasty material and it's going to have one ion in it. And then you've got a separator, kind of like we did in our test tubes earlier. And then there's an electrode right in the middle. So you have a cap that's going from the electrode and you have another cap that's going to the other electrode that's connected only to the outside. Many of the batteries, the casing itself is part of the actual chemical cell. So all these are basically the same. If we want to have, like with our 12 volt car battery, if we want to have more than one and a half volts, we have to do this. So if we want to have nine volts based on the standard reduction potential table, we can't get but about one and a half volts. So we would need to have six times one and a half will give us the nine volts that we're looking for. So they're just packaged together so that we can get nine volts from this. Some manufacturers make them like our AAAs, a little bit smaller. And some manufacturers make them in a stack. So one, two, three, four, five, six, six, one and a half volts stacked together is going to give us nine volts. Here is an example of a D cell. And you can see the housing is metal. This is connected here. You'll see that this is just part of the casing, which is acting as a conductor. On the other end, there's an insulator and you can see the electrode. So this is protected by a nonconductor, that piece of plastic right there, so that there's a separation between the canister itself and that electrode. And then the whole container has the pasty-like material like we had in the AA. Most of these are called alkaline, and that's because the liquid that's in the paste is hydroxide. And so it would be very caustic and it would burn your hands or your eyes. So that's the reason these are sealed and you don't open them. So what we want to think about is that what I've talked about here is primarily using a battery to produce energy. If we reverse the reaction, we can use it to store energy. If you have a solar cell and you want to have electricity at night, you're going to have to have a storage battery. If you have an electric car, you want to drive it, you are going to have to have a lot of batteries. And that's what makes electric cars pretty expensive is you have to have a lot of power, not just 12 volts. You've got to have a lot more than that to power your vehicle.