How Batteries Work

This kind of falls in line with some of our earlier podcasts. You may remember our Basic Electronics podcast that we did ages ago, and this kind of falls into that same sort of category. We wanted to kind of talk about what batteries are, how they work, and kind of just sort of give you a basic understanding. Now, the interesting thing about batteries is that it involves a lot of chemistry. So we should have given this to

that science podcast. Well, part of the reason that I suggested doing batteries, and so it sort of came to me when I was working my way through a book called Empires of Light, which is a um history of electricity. Basically what by Jill I'm probably pronouncing your name wrong, Jonas j o n. And he asked, may maybe even be Jones. But it's really uh, wellly so far, I'm about a third the way through. The book's really interesting and they and uh As Jill started working through the

basics of the history of electricity. Part of the early history, of course, involves batteries because we weren't exactly plugging stuff into the wall. Uh, really much past the early part of the last century, you know, a little bit into the nineteenth century, but really it's a twenty and twenty

one century, you know. Yeah, And uh to add on to that, I mean, I have an interest in batteries because it helps explain how absolutely ridiculous the robots and computer's plan was in the Matrix to turn humans into giant batteries, because really that's an incredibly inefficient way of getting your power supply. That's a very good point that I hadn't thought of. Yeah, I didn't think you would have, um because it really has no other bearing on this discussion.

It was just me trying to throw in yet another reference to a science fiction film. By the way, I still love that first Matrix movie. I just I refuse to acknowledge the other entries in that series. But let's talk about batteries. Yes, and as it as it turns out, batteries are quite old. Yeah. We're not talking about the batteries in your closet. I mean those might also be

quite old. We're talking about the actual concept of batteries themselves. Yes. Um. Actually one of the very first things that made me think about it was the Layden jar, the reference to the Laden jar and Empires of Light uh, which was created created in Leyden in the Netherlands. UH professor Peter

van Mussen Muschenbrook and his friend Andrea s. Cuneus. We're working on an experiment in the mid eighteenth century, and what they discovered was they could take a jar UH line it with a metal film on the inside and outside about the bottom two thirds of the jar UH, and with an electrolytic liquid inside. They could put a metal rod down into the jar with a with a cork uh to to cap off the battery and it would store an electrical charge. Was it turns out, uh.

You know, I had always heard of that as being one of the very first examples of a battery, but back in ninety eight, UM a an archaeologist, a German archaeologist named will Wilhelm kronig Uh found a clay jar UH containing a copper cylinder with an iron rod in it. And apparently the people living in the area around Baghdad had batteries as old as well. They think they're pretty

sure it's a battery. There's no proof, but the design is very, very similar to the laden jar and these existed as possibly as far back as two b c. Well, what's interesting is they found those clay jars in a giant stone statue in the shape of a rabbit carrying an enormous drum. Okay, that's that's a lie, but you may you may remember what Chris is talking about if you if you're a fan of the show MythBusters. Yes, MythBusters did an episode about these clay jars and whether

or not the devices themselves could be batteries. One of the theories, or i suppose a hypothesis that was put forward, was that these were part of a religious or spiritual ritual in which you would feel a tingling sensation by holding the these jars and you know, essentially completing a circuit that you you would feel the that tingling as the electricity moved through you because it was a very low voltage and a really low current, so it wasn't

it wasn't going to actually cause damage. As I recall on that episode, they ended up rigging the clay jars they made with an actual electric circuit and shocked um atom as I recall, and to a point where Adam was very displeased. Uh, because it could have been potentially very dangerous. But but yes, that's a good example. Those those may very well have been batteries. Now what were they powering? Probably not ancient iPods No. Um. According to the BBC article that I found on it, which dates

back a couple of years. UM, it is possible that they were being used for electroplating with gold. UM. Basically, uh, you know, using the electric current to plate things with a very very thin layer of gold or silver. Um. There's no proof again that there's no documentation. Apparently the instruction book is long gone um and um, but there there are no the thing is what you were talking about with the MythBusters show. Um, there's no wiring that

went along with it. So it doesn't appear as though they were wired in a series and even with as with the Leyden jar um, they found out that although these these uh you know, we'll call them primitive I guess batteries uh can store electricity, they can't store that much. The replicas of the clay jar uh batteries from the Baghdad Fine generally produce around zero point eight two volts each. But when you wire them in series or no, i'm sorry, in parallel, in parallel, um, then you can produce a

much larger charge. It's just that they didn't find anything like that. So they could have been used in a religious ceremony to prove uh, the the deification of someone. If you get the shock one time and you don't the other time, I mean like, oh wow, this this power. They have this power. Obviously they are divine in some way or for electroplating. Both they both examples are kind of interesting, but there's no right and uh And going to what you said about series and and parallel, that's

a good thing to mention really quickly. Um, if you are hooking up batteries in parallel, that means that you're not hooking them in to end. They are all hooked into a circuit of some sort, some sort of of wiring pattern where UH, that increases the current that the batteries are able to supply. If you link them in series, which is essentially end to end, that increases the voltage

but not the current. So series is increase in volts, UH, parallel is increasing current and in either case they do not affect the other, right voltage, voltage is increased, current remains the same, or current is increased, voltage remains the same. UM, let's talk about another early battery, UH, the voltaic pile. Yes, this was a battery that was built by Alessandro Volta

in eighteen hundred. And what Volta did was he discovered that by creating layers of zinc, a some sort of of of separator which he used blotting paper that had been soaked in salt water and silver. Then I'm sorry, silver was the other layer. So had zinc this blotting paper that was soaked in brine essentially then silver, and UH found that that would also allow a transfer of electricity if you created a wire between the top and bottom. Not to argue with you, but in the research that

I did, Britannica said that it was copper and zinc. Well, it may very well be In our article on our site it says silver. We'll have to look into that, and that's wrong. We'll have to fix it. Yeah, we can fix it in our article that's where the wonderful things about the Internet. Actually, they may in a way, they may both be right, because these early experimenters were trying a number of different metals. You see which ones were more. They may both work. But obviously we know

that copper is an excellent conductor of electricity. Um, and uh, it is possible that he could have built one that way too. Yeah, it's actually it is true that you can try various combinations of different metals. The most important thing is that the metals have to have. Uh, you have to have a positive electrode and a negative electrode. Right, you have to have one metal where there's going to

be an excess of electrons. That means it's going to be the negative one because electrons carry a negative charge. That that would be the anode and the other ones the cathode, which has the an absence of electrons, meaning it has a positive charge. Now, as we know, negative is attracted to positive and vice versas, so electrons want to go where there is going to be a more positive charge. They don't want to be where there's a heavy negative charge because like repels like you know, as

far as charges go. So the trick here is to create a situation where you have a negatively charged and a positively charged electrode close to but not touching each other, suspended in some sort of solution which we call the electro light, which allows the passage of ions but does not allow the passage of electrons to go between the two. Then you hook the two up with a wire of some sort which would create a pathway for electrons to flow through. And you could actually do this yourself if

you really want. You can take a battery and put a wire on one end and a wire on the other end, the two terminals the negative and positive terminals, and that would create the connection needed for the chemical reaction to take place that produces electricity. It would also

kill your battery really quickly. Yes, um, you normally would want to put a load on that wire, a load being some sort of something being powered by that electricity, like a light bulb would be a class one right yes, or a fan or a motor or an iPod, right yeah, And and So what happen is the the electrons from the negative terminal would flow through the wire, would go to whatever the load was on that wire, power whatever it was, and then continue on the way to the

positive terminal. Now, once HiT's the positive terminal, the electrons start to recombine with various ions that've been generated by this chemical reaction within the battery. And depending on the type of battery, it may mean that the battery is slowly losing its ability to generate power and it won't regain it and like once you use it, it's gone.

That's while a lot of the batteries are when you go into like an electronic store and you're just buying double A batteries or something along those lines, most of the batteries fall into that category. I mean, you can't get rechargeable batteries, and that's a totally different discussion. But the in general, what we're talking about here is the chemicals that are that make up the composition composition of

the battery, um the various electrodes. As this chemical reaction happens within the battery and it generates these electrons and the electrons recombine, uh, you lose more and more of the active elements of that battery, until eventually the resistance of the battery is so high that you are no longer generating electrons or you know, you're not creating that flow.

That also explains why let's say that you have a flashlight you've got you know, you leave the flashlight on, you know how the flashlight eventually gets dimmer over very gradual time frame and then eventually I'll just go out. Uh. Well, that could be indicative of two things. One your lightbulb could be burning out, or two the batteries are starting to lose their their uh potency, the resistance within the battery,

because there is an internal resistance inside the battery. That resistance grows as those chemicals get used up in these reactions so that it's able to put out fewer electrons. The voltage begins to drop, and that's why you start to see that gradual depowering. Yeah, Volta saw that in his voltaic pile. Um because basically what happened just sounds so disgusting. UM because of course the salt water is going to dry up and in the in the voltake device and UM. At that point, the that the chemical

reaction is not going to take place anymore. But also oxidation that's going on, what he said, because that actually uses up the metal. I'm sorry i jumped ahead. I didn't realize you were going to say that too. Yeah, oxidation that the electrochemical reaction that happens inside of batteries, an oxidation reduction reaction, which means that one of the elements within that reaction is is oxidizing and one's reducing. Now it's funny because reducing doesn't mean what you necessarily

think it means. It's actually the whole oxidation reduction thing is one of those things that always confused me in physics class um. But reduction is actually a gain of electrons. An oxidation is a loss of electrons. That's why it's That's why it's confusing, Right, you're reducing, but you're gaining electrons. You're actually it's it's a whole thing. It also turns into it's because you're you're needed to focus on the oxygen, not the electrons, is the problem. But at any rate,

that's the kind of reaction that's going on. And yeah, if you run one of these will take piles long enough, the you kind of get this corrosive material that ends up being unusable for batteries. By the way, you can build your own voltaic pile. It's not very difficult at all. Um In fact, let me give you a recipe. This is a very easy way. Now, granted you're not gonna be able to power anything with this necessarily, but you

might be able to detect the voltage. If you have a very sensitive voltmeter, you might be able to to to see how much charge you are creating. But what you can do is you get some nickels, and you get some pennies. Um Or you could use dimes and pennies if you wanted to, but nickels and pennies are pretty simple. And you get uh, some paper towels, and you get some water and some salt. All right, you

create a solution with the water and salt. You put as much salt as the water can hold in solution, and then you soak the paper towels in that brine solution you've created, and you start to build layers, and you do a nickel, You do the paper towel, penny

paper towel, nickel paper towel, penny paper towel. The taller you build that tower, the greater the voltage you will generate UM and it should increase the same amount through each each element of that bill take pile that you've added each each three part element, the penny nickel and paper towel layers UM and uh it's just a very bowl simple uh um experiment you can do. You can also, of course you probably have seen this. You can make batteries other things like a potato. You have to use

the correct kind of electrodes. But if you put the two electrodes within a potato close enough so that the electron exchange can occur or the ion exchange I should say can occur, but not so close that they're actually touching, because then you just create a short circuit. The potato will facilitate the electro light transition of ions. So you can power like a tiny light bulb by light bulb, I mean led light UM. And you can even hook

potatoes in series. And the best thing about this experiment is after you are done lighting up your room with l e d s powered by potatoes, you can have French fries. There is there are some intermediary steps. By the way, they don't l D s do not turn potatoes into French fries. Belgians do. I'm a fretz. So So anyhow, in doing research, Jonathan reminded me of this Energizer you know, the battery company website, and uh, it basically shows you an illustration of the different parts that

make up today's battery. And in some ways it's very similar to those very early batteries. It's just more powerful and and more efficient, but much more compact. Yes, that that's true. Um also um like like as we were talking before about the experiments done by the early philosophers who were investigating batteries and electricity. UM, depending on the manufacturer and the application, they may use different materials for the cathode and anode and uh, you know, even the

electrolyte inside, depending on the purpose. Of course, they're always trying to get a better, more efficient battery. But in the case of the Energizer battery, UM, the cathode is the case which is made up of manganese dioxide mixture. Yeah. Yeah, there's a there's a steel tube essentially, like that's that's the outside of the battery, UM, and that that's part of the cathode. So you've got that steel tube and

then which of course is capped on both ends. Uh, And then the interior of the tube is coated with this manganese dioxide mixture. It's a powder and um and yeah, that that's the the cathode. So that's carrying the the what they call the positive electrical charge, which sounds so confusing when you sit there and think, oh wait, electrons are negative. But essentially this is the positive element, right,

This is what's generating the positive ions right right. And um, of course, as in uh Volta's experiment, UM, you need a separator UM which is made of an energizer's case again a non woven fibrous fabric, and the website actually says that the anode is made of powdered zinc. Ah. Okay. So the the operator's job here is mainly just to make sure that the anode and cathode do not touch, because that would generate essentially a short circuit. You would

no longer have a working battery. It would be it would It would just be useless, is what would be. And it will also possibly generate a lot of heat. Yes, think of it as the battery chaperone. Now you too, art So anyway, the zinc acts as the the the anode, that's the so that's this is the negatively charged um material. And then you have the electrolyte, which is the potassium hydroxide that is inserted in this. That's what's allowing the facilitating the passage of ions between the anode and the

cathode um. And then you've got the positive terminal and the negative terminal. You hook the you put out of the right right, Yeah, outside the battery, So back to the steel part. You've got a positive terminal and negative terminal. Oh and I forgot, there's a collector. A collector. Yeah, there's a brass pen that is inserted the The base of the brass pin acts as the negative terminal, so

that's where all the electrons are coming through. But the brass pins job is to act as a conduit for electrons. So so at the very center of an energizer battery is this brass pin. You hook the plug your battery into whatever device you're talking about, you know, like a

flashlight will stay with that. The electrons will go through the negative terminal, through the circuitry of the flashlight, powering the bulb, and then back in through the positive terminal, and through that process, the manganese dioxide and the zinc are going to start turning into this these inert forms where they are no longer charged one way or the other. And uh, eventually you start to run out of the active components and you've got a dead battery. Right. Also

keep in mind, just gonna throw this out there. Remember electricity flows one way, current flows the other way, because Benjamin Franklin thought that current was carried by positively charged particles, not negatively charged. Once, as it turns out, the answer

was negative. So anyway, so that just happened. But yes, the Energizer web page does have very helpful illustrations and animations kind of showing you not just how the batteries work, but how Energizer builds these batteries, the various elements that go into it, and exactly what happens while you're powering the device. So it's um, it's it's a nice little uh website kind of a tutorial. Um, if you want

a more visual element to this discussion. Yeah, and it really gets into how uh Energizer makes alkaline batteries, which is, you know, basically this the standard type that you find on the on the counter at your local store. Now, there are other kinds. Of course, we mentioned chargeable batteries, but there are are lithium batteries UM, which are a little weird according to UH, to the research I had done on Britannica UM, there is no separator between the

anode and a liquid cathode. UH. But as but a a layer automatically forms on the lithium, which basically makes it its own separator. UH. This, this layer as it forms is I guess as it's being used, was at least my understanding of that UM. And that allows a much more high power density, which is why you see them the lithium batteries advertised as a more powerful battery

for applications such as cameras, digital cameras. I see them often advertised in that for that particular application because they have a higher power density. But it have a longer shelf life. Yeah, they do, they do, and it's apparently because of the metals used inside. They're also more expensive. Yeah, these are the kind of batteries. The small ones are the kinds that power things like UM like electric hearts. You want, you want a battery that's gonna last a

really long time for that kind of thing. Clearly, you don't want to have to pop open, pop it open and switch the nine vold out every couple of weeks. That would be irritating. But yeah, there's there's carbon, zinc batteries, zinc chloride, there's um mercury batteries, silver oxide batteries, zinc air batteries, and there's lots of different types. And all

the ones I just named were non rechargeable batteries. So you know what, I think we should probably do another episode in the future about rechargeable batteries as well as a kind of a discussion about some of the things that can happen when batteries go wrong. Yeah, I think I think that would be, uh, that would be very good. Now, of course, uh, you know, it's possible that an alkaline battery will if you leave it in a device for

too long, it will eventually corrode. Yes, but there are other instances to like car batteries, and the chemicals inside batteries can be caustic, so you don't and you've got to remember that the steel canisters that surround the batteries keep that those those elements under pressure, not the Queen uh David Bowie song. However I am singing and now I am too. It's a terror of knowing what those

world is about. But anyway, the the batteries keep that those elements under pressure, and if you puncture it then you could get squirted by some caustic stuff. So you don't want to do that. You don't ever want to you know, break batteries open or anything like that. And there's also the corrosive element where if the battery is left for too long, that can happen. Um Also things like if a battery gets too cold, it can take a really long time for those chemical reactions to start

up because they often are affected by heat. And if it's too warm, um, it may not it may have already like that, it may not perform as well. Either. There's usually a range of temperatures at which a battery is optimal, and then outside that range you're gonna get a decrease in performance. But in general, like if you've ever heard if you want your batteries to last longer, put them in the freezer, don't do that. It's a bad idea. No, that's not a good idea at all.

All right, Well, let's wrap up this initial discussion of batteries. We can revisit the topic in the future and talk about some of the other issues and problems that we run into, as well as how can a battery be recharged if you're using up these chemicals. It's actually pretty interesting. Yeah, I agree. I was actually surprised by the answer. Yeah. Yeah, it turns out it is not magic um and that

means io Chris a coke. Unfortunately, we have them for free here, so I'm not out any money, uh, Jonathan, And um, actually this was just handed to me. It looks like how stuff works dot Com now has an iPhone app. See it's awesome. Yeah. Actually, um, I got to take a look at this earlier. And guys, this is pretty cool. The iPhone app is sort of a way to integrate all the cool stuff we do at

how stuff works dot com. So you guys may have listened to one of our podcasts and we talked about there's this great article on the site, but you're not

at your computer, so you can't really check it. Well, the iPhone app actually lets you browse articles and blog posts, even lets you interact on Facebook and Twitter, and you can listen to podcasts at the same time, and it has all the house stuff works dot com podcasts on it, not just ours, but you know good ones too, so you can listen to those and look at the articles and and go on Facebook and Twitter and it should

work perfectly with your iPhones and iPod touches. Awesome. Well, it's uh, it looks like it's now available on the iTunes store, so that's good to know. How much does it cost? It's freeze sweet? All right, Well, that wraps up this discussion on tech Stuff about batteries. If you guys have any questions or suggestions for topics, you can contact us through Twitter or Facebooks are um handled. There is tech Stuff h s W or you can email us.

Our email address is tech stuff at how stuff works dot com and Chris and Ill taught to you again really soon. For more on this and thousands of other topics, visit how stuff works dot com and be sure to check out the new tech stuff block now on the how Stuff Works homepage, brought to you by the reinvented two thousand twelve camera. It's ready, are you