[Applause] the standard household alkaline battery we use these every day all over the world but how do they work that's what we'll be covering in this video which is sponsored by squarespace head to squarespace. com to start your free trial or use code engineering mindset to save 10 on websites and domains a battery is a device used to store energy for a later point when we need it we use batteries to power small electrical devices such as a flashlight the energy is stored as chemical energy and this can be turned into electrical energy for when we need it if we look at a simple battery and lamp circuit to illuminate the lamp we need lots of electrons to flow through it the battery is going to provide the pushing force which allows electrons to flow through the lamp we simply need to connect the lamp across the positive and negative terminals of the battery to complete the circuit the battery can only push the electrons for a certain amount of time though this time depends on how much energy is stored inside the battery and how much is demanded by the load when we talk about load in an electrical circuit we mean any component which requires electricity to work these could be things such as resistors leds dc motors or even entire circuit boards some batteries can be recharged and it will clearly state this on the side of the battery but the typical household alkaline battery can't so this is simply disposed of when it runs out of energy these can be recycled though so do ensure you dispose of these responsibly by the way if you want to learn how a dc motor works then we've covered that in great detail previously do check that out links in the video description down below a typical 1. 5 volt alkaline battery looks something like this but the colors will vary by manufacturer when we look at a battery we usually have a plastic wrapper fitted tightly to the outside this will insulate the battery but also tell us important information such as the capacity and the voltage as well as which end is positive and negative the positive end is known as the cathode and it will have this extended surface which protrudes outwards the negative end is known as the anode these two terminals are electrically isolated from each other under the wrapper we find the main casing which is usually made from steel with a nickel plating this holds all the internal components in place and stops them from interacting with elements of the atmosphere such as air and water within the casing we have multiple layers of different materials these materials are specially selected because their chemical reactions create certain levels of voltage and current the first layer is the anode which is a mixture of manganese oxide and graphite the graphite is added to improve the conductivity of the mixture and increases the energy density next we find a layer of porous material typically a fibrous paper which forms a barrier the barrier prevents the anode and cathode materials from having direct contact with each other this helps the battery last longer when it's not being used if the barrier wasn't there then the battery would short circuit the microscopic holes within the material allows iron atoms to pass through it again we'll look at that in detail a little later in this video an electrolyte liquid of potassium hydroxide is then sprayed onto the separator during the manufacturing process this will soak it and it will be absorbed into the anode material the electrolyte used is an alkaline which is why we refer to this type of battery as an alkaline battery on the other side of the barrier we have an anode which is a paste made from zinc powder as well as a gelling agent the gelling agent just keeps the zinc suspended so it doesn't accumulate in one spot the zinc is in a powder form to increase the surface area of the material which lowers the internal resistance and thus improves electron transfer the steel capsule is sealed with a nylon plastic cap a brass pin is then inserted into the zinc with a steel cap placed over this this gives us the negative terminal notice that the positive and the negative terminals are separated by the plastic cap this ensures they are electrically isolated from each other otherwise electrons could flow through the casing to reach the positive terminal and short-circuit the battery we need to understand some fundamentals of how electricity works before we can understand the battery firstly electricity is the flow of electrons in a circuit batteries can provide the pushing force that moves the electrons through the circuit the electrons want to get back to their source and they will immediately take any path that's possible to achieve that by placing things such as lamps in the way of the electrons we can force them to do work for us such as illuminating the lamp batteries produce dc electricity or direct current this means the electrons flow in just one direction from the negative to the positive an oscilloscope will show dc as a flat line in the positive region you can think of dc electricity like a river which flows in just one direction in these animations i show electron flow which is from negative to positive but you might be used to seeing conventional current which is from positive to negative electron flow is what's actually occurring but conventional current was the original theory which is still widely used and taught to this day just be aware of the two and which one we're using the electricity you get from the power outlets in your homes provides ac electricity or alternating current this is different than the electricity provided by a battery with alternating current the electrons flow forwards and backwards continuously much like the tide of the sea which flows in and out between high tide and low tide an oscilloscope will show ac as a wave running through both positive and negative regions because it's flowing forwards and backwards through positive and negative if we look at a section of copper wire inside the wire we find copper atoms at the center of an atom we have protons and neutrons the protons are positively charged and the neutrons are considered neutral so they have no charge orbiting these are electrons electrons are negatively charged some of these electrons are free to move to other atoms they will naturally move between other atoms but in random directions which is of no use to us we need electrons to flow in the same direction and we can do that by providing a voltage difference from a power source such as a battery when we talk about atoms you will usually hear the term ion used an ion is just an atom which has an unequal amount of electrons or protons an atom has a neutral charge when it has the same number of protons and electrons because the protons are positively charged and the electrons are negatively charged so they balance out if an atom has more electrons than protons then it's a negative ion if the atom has more protons than electrons then it's a positive ion voltage is like pressure in a water tank to know how much pressure we have we must compare the pressure inside the pipe to the pressure outside and we use a pressure gauge to do that when it comes to voltage we use a voltmeter to measure the difference in voltage between two different points if we measure the difference across a battery we get 1.
5 volts but if we were to measure the same end then we would get 0 volts because it's the same end so there's no difference some materials allow electrons to pass through easily these are known as conductors copper and most metals are examples of this other materials do not allow electrons to pass through these are known as insulators rubber and most plastics are examples of this that's why we use copper wires with rubber insulation the copper transports electricity to where we need it and the rubber keeps us safe by mixing certain materials together we can cause chemical reactions this is when the atoms of one material interact with the atoms of another during this interaction atoms will bond together or break apart electrons can also be captured or released by atoms during the chemical reaction okay now that we have the basics covered let's have a look inside the battery and see how it works remember we talked briefly about atoms well all these different materials inside the battery are made from lots of different atoms tightly packed together these are represented by the coloured balls and each color represents a different material and therefore a different atom when we combine all these materials together inside the capsule we're going to get a small chemical reaction where the atoms start to interact with each other first of all a hydroxide ion atom within the electrolyte is going to join with a zinc atom inside the anode section this chemical reaction is known as oxidation and will create zinc hydroxide as the zinc and hydroxide combine it will release electrons these electrons are now free to move and they will collect on the brass pin at the same time a manganese oxide atom is going to join with a water molecule from the electrolyte as well as a free electron in a chemical reaction known as reduction during the chemical reaction the manganese oxide turns into a slightly different version of manganese oxide this version no longer needs a hydroxide iron atom so it will eject this into the electrolyte the water atom is replaced by the one ejected from the oxidation reaction the hydroxide ion is now free and able to pass through the separator so as you can see we have a buildup of electrons at the negative terminal as the electrons are negatively charged we now have more electrons at the negative terminal compared to the positive which means we have a voltage difference between the two ends and we can measure that difference with a multimeter remember we can only measure the difference in voltage between two different points electrons repel each other and want to move to a region with less electrons the positive region has less electrons so they will try to reach this terminal the separator prevents them from flowing inside the battery to reach the positive terminal therefore the electrons need another root if we provide the electrons with an external path such as a wire the electrons will flow through this to get to the positive terminal by placing things such as a lamp in the way of these electrons the electrons will have to pass through this and so we get them to do work for us such as illuminating the lamp as long as we have a complete circuit between the terminals the chemical reaction will keep occurring and the electrons will flow from the negative terminal if we remove the wire or break the circuit then the chemical reaction stops so let's recap on the chemical reaction that's occurring the free electrons are entering the battery through the positive terminal this combines with a manganese oxide and a water molecule at the cathode which releases a hydroxide ion into the electrolyte the hydroxide ion passes through the separator and joins with a zinc atom to create zinc hydroxide and as this happens electrons and a water molecule are released the electrons want to get to a region with less electrons the positive terminal has less electrons so they will flow through the wire to reach this and so the chemical reaction repeats again and again continuously however there's only a certain amount of material inside the battery so over time this is going to become harder and harder for the chemical reaction to continue and eventually no more electrons will flow at this point the battery will be of no further use and it will have to be disposed of we can use a battery to power some components but usually a single battery isn't enough to power our devices for this we need to combine the batteries we can connect batteries in two different ways series or parallel we have covered these circuit types in great detail previously do check those out links can be found in the video description down below when we connect the batteries in series the voltage of each battery is added together so two 1. 5 volt batteries gives us three volts and three batteries gives us 4. 5 volts the actual voltage might be slightly different in the real world the voltage increases because each battery is boosting the electrons that enter it so we get a higher voltage if we connect the batteries in parallel then we only get 1.
5 volts regardless of how many we connect together that's because the path merges at the supplier but splits the return so the electrons will not be boosted however this configuration type will be able to provide more current and it will also have a larger capacity so we can power something for longer for example if the battery had a capacity of 1200 milliamp hours and we placed two in parallel then we will have a capacity of 2 400 milliamp hours but a voltage of only 1. 5 volts if we wire them in series we now have a capacity of just 1 200 milliamp hours but a voltage of 3 volts we use batteries to power our circuits but how long can a battery power our circuit for when we look at the packaging or data sheet for a battery we see a value with the letters mah next to it this is the milliamp hour rating for example this one has a rating of 2 500 milliamp hours that tells us it could theoretically provide a current of 2500 milliamps for one hour or 1250 milliamps for two hours or 20 milliamps for 125 hours however in real life it probably won't actually last this long because the chemical reaction slows so the internal resistance of the battery changes as it empties there are lots of other things that affect this such as the age and the temperature there's no real way to precisely calculate the life span the best way is to simply test it we can however make an estimate of the lifespan with the following formula the battery life equals the capacity in milliamp hours divided by the circuit current in milliamps so for example in this circuit we calculate a demand of 19 milliamps and the battery has a capacity of 3 000 milliamp hours so 3 000 divided by 19 gives us 157. 9 hours but this really is the best case scenario though and in reality it almost certainly won't achieve this we have also built a free simple calculator on our website where you can estimate the runtime of a battery as well as the required capacity do check that out links can be found in the video description down below to measure the voltage we simply need to select the dc function on our multimeter and then we connect the red lead to the positive terminal and the black lead to the negative this will give us a voltage reading you can see that this battery is rated at 1.
5 volts but when we test it we get 1. 593 volts the two values are close but usually not the same when the battery is dead or dying we get a lower voltage this one for example reads 1. 07 volts so it's completely dead however sometimes we could still get a voltage of around 1.
5 volts even if the battery is of no use to fully test the battery we need to test it under a load condition to check whether it's still useful and for that we need a resistor so we take a resistor of around 100 ohms but it doesn't have to be exactly this value though we connect the resistor between our two probes in this case i've just used some crocodile clips to connect the resistor between the probes like this this way current will flow through the resistor and we can take a voltage reading as this occurs if the battery is still good then the voltage level will only drop slightly for example this battery has a rated voltage of 1. 5 volts with no load it is 1. 593 volts with the resistor connected we take a reading of 1.
547 volts so this battery is still good however this battery is also rated at 1. 5 volts when we take a measurement with no load it oddly has a reading of exactly 1. 5 volts but when we connect the resistor we can see that the voltage has dropped to 0.
863 volts so we know that this battery has run out of charge but now that you are all charged up check out squarespace. com to create your own online web presence which is packed with features to empower individuals to launch share and promote their own projects there's powerful blogging tools to showcase your project photos videos and progress updates you can easily schedule appointments for classes and sessions with team members or clients through their inbuilt tools and you can even collect payments or donations to help support your cause head to squarespace. com for a free trial and when you're ready to launch go to squarespace.
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