How A Car Battery Works - basic working principle

[Applause] the 12 volt lead acid car battery these large and fairly heavy batteries are used in every combustion engine vehicle on the planet they're an essential part of the vehicle so what does it do and how does it 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 the 12 volt car battery looks something like this this is a lead acid battery we call it a lead acid battery because inside the unit are lead plates which are submerged into an acid this creates a chemical reaction which releases energy and provides us with a voltage and current the battery is therefore storing energy in the form of chemical energy it does not store electricity this chemical energy is converted into electrical energy whenever we need it this battery is also rechargeable if we supply the battery with electricity then we can reverse the chemical reaction and recharge the battery these types of battery provide large amounts of current especially compared to the typical smaller household alkaline batteries we have covered how alkaline batteries work in our previous video do check that out links can be found in the video description down below the typical car battery is found in the engine bay of the car the battery is first used to start the engine and it does this by providing electricity to a small electrical motor known as the starter motor the starter motor engages a small gear onto the flywheel of the engine it turns this to turn the crankshaft which starts the combustion engine the small gear then disengages and the engine runs by itself the starter motor needs to provide a huge amount of force to be able to turn the flywheel so the starter motor will draw an extremely large current possibly hundreds of amps but this is only for a few seconds this large current demand is going to reduce the energy storage of the battery so we will need to top this back up connected to the engine is an alternator the alternator is rotated by the engine and as it rotates it generates electricity this electricity is fed back into the battery to recharge it while the engine is running the alternator recharges the battery but it also provides the electrical power for things such as lighting and the music system when the demand for electricity in the car exceeds what the alternator can provide then the battery will provide this additional power which again drains the battery if the engine is switched off the alternator stops rotating and recharging the battery so the battery will provide the full electrical power to the car until it's dead at this point the battery can't provide enough electricity to start the engine so we will need to jump start the car let's have a look at the main parts of a car battery and then we will understand how it works first of all we have the plastic case which holds all the internal components in place on the top we have the plastic lid and there are two terminals a positive and a negative by removing the lid we can see inside notice the casing is divided up into six separate chambers each separated by a plastic wall each chamber is known as a cell each cell generates around 2.1 volts of dc or direct current each cell is connected in series the negative of one cell is connected to the positive of the next cell to give us a total voltage of around 12.6 volts it's the same as if you connected household alkaline batteries together the voltages add together to provide a higher total voltage each cell in the battery is connected via a plate strap this is made from lead these straps are welded together through the plastic wall to form the connection as we look at the battery from this view we see that current flows through the battery cells from the positive to the negative and that's using conventional current theory but what's actually happening is the electrons are flowing in the opposite direction from the negative and to the positive but we'll cover that and you'll see why a little later in this video notice there are two plate straps in each cell one positive and one negative these are called plate straps because each strap is connected to a number of plates which are sheets of lead the plates are formed into grid type structures which maximizes the surface area the grids are coated in a paste of lead oxide the paste is where the chemical reaction occurs and we'll see that a little later in this video the paste acts a bit like a sponge and is going to absorb some of the electrolyte liquid which improves the battery performance the size of the plate determines how much current a battery can provide but it doesn't change the voltage the materials used for the chemical reaction and the number of plates determines the voltage produced by each cell the grid holds the paste in place to ensure a uniform current distribution across a plate and helps to transport the electrons out of the battery and around the car's electrical circuit the negative plate is the anode and this is a plate of pure lead although some small amounts of additives are added to harden the lead and protect it from corrosion the positive plate is the cathode and this is made from lead oxide the plates are made of dissimilar materials to form the chemical reaction and release the electrons now we don't want the positive and a negative plates to come into direct contact with each other because this would short-circuit the battery so instead we place each positive plate into an envelope separator this is just a porous material that allows ions to flow through it without the materials coming into direct contact with each other the positive and the negative plates will sit between each other with a small gap in between each plate the chamber is then filled with an electrolyte liquid of sulfuric acid and water hence the battery is called a lead acid battery i want to quickly recap on the fundamentals of electricity so that you understand the next part of how the battery works electricity is the flow of electrons in a circuit we need lots of electrons to flow in the same direction through a wire so that we can place things in the path of the electrons such as light bulbs the electrons will therefore have to pass through this and as they do so they will produce light when lots of electrons flow in the same direction we call this current every material is made from atoms the atoms have different numbers of protons neutrons and electrons which is what makes them a different material some materials like copper have an electron which is free to move to other atoms if we connect a power supply such as the battery to the copper wire then the voltage of the battery will push the electrons and they will rush to get to the positive terminal of the battery now i just said that the electrons flow from the negative to the positive this is known as electron flow it's a theory of how electricity works and it's what's actually occurring but you might be used to seeing conventional current which is from positive to negative this is the original theory which is known as conventional current this theory was proved wrong by joseph thompson who discovered the electron and he found that they flowed from the negative to the positive however we still to this day use conventional current theory when designing electrical circuits so if we looked at this simple circuit we must always assume that the current is flowing from the positive and to the negative but engineers and scientists know that electrons are actually flowing in the opposite direction the electrical formulas we use will still come out with the same answers regardless of which way the electricity is flowing so it doesn't really matter there are two types of electricity dc direct current which we get from batteries the electrons in this type are pushed in one direction so it's called direct current think of this like water flowing down a river the other type of electricity is ac or alternating current which is what you get from the power outlets in your homes in this type the electrons are pushed and pulled forwards and backwards think of this like the tide of the sea flowing in and out between its maximum high tide and its maximum low type when we mix certain materials together we can cause chemical reactions this is when the atoms of one material interact with the atoms of another material during this interaction atoms will bond together or break apart electrons can also be released or captured by atoms during this reaction when we talk about atoms you'll usually hear the term ion used an ion is an atom which has an unequal number of protons or electrons 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 the 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 rather than trying to understand this complex construction we're going to simplify it down to this simple model of a cell with a single cathode and anode in this cell we have the electrolyte liquid which is one-third sulfuric acid and two-thirds water we have the positive electrode which is the cathode this is made from lead oxide we then have the negative terminal which is the anode this is made from pure lead when these materials are combined we're going to get a small chemical reaction between the atoms i'll show the atoms of these materials with these coloured spheres the positive cathode terminal of lead oxide is going to react with the sulfate in the electrolyte this will form a layer of lead sulfate on the cathode terminal during this reaction an oxygen ion is ejected from the cathode and into the electrolyte once in the electrolyte these oxygen ions will combine with the hydrogen ions to form water at the same time the lead atoms on the anode are going to react with the sulfate ions in the electrolyte this reaction will create a layer of lead sulfate around the electrode during this reaction two electrons are released and collected in the negative terminal so now we have a buildup of electrons on the negative terminal as electrons are negatively charged this means we have a difference in charge across the two terminals and we can measure this with a voltmeter or a multimeter if you think about a magnet the electrons are negatively charged and so they repel each other these are attracted to the positive terminal which has less electrons however they can't reach this yet so if we provide a path for the electrons such as a wire then the electrons will flow through this to get to the positive terminal we can then place things such as a lamp in the way of these electrons and use them to do work such as illuminating the lamp while the path exists the chemical reaction continues but this won't last forever the chemicals required for the reaction will run out the acid becomes diluted and weaker and a buildup of lead sulfate coats both of the electrodes this means the materials of the electrodes are becoming more similar and so the chemical reaction becomes harder to achieve but luckily this chemical reaction can be reversed so if we supply the battery with electricity from the alternator we can start to reverse the reaction the electrons enter the negative terminal and rejoin with the lead sulfate releasing the sulfate into the electrolyte to leave just lead on the negative plate the sulfate ions enter the electrolyte and combine with the hydrogen ions to release the oxygen ions and so the electrolyte acid becomes stronger the oxygen ions combine with the lead to create lead oxide and this releases the sulfate back into the electrolyte making it even more stronger if we were to leave the battery to fully discharge for too long or too many times it becomes very difficult to reverse the chemical reaction additionally the sulfate layer could break away from the electrodes and accumulate at the bottom of the battery this means it will no longer participate in the chemical reaction so the battery needs to be repaired or replaced so when we look at the battery this chemical reaction is occurring between every plate in every cell to provide the hundreds of amps of current to start the motor and also provide the voltage to power the lights etc this is then recharged by the alternator to test the voltage of a car battery we simply switch to the dc voltage setting on our multimeter and then connect the red lead to the positive and the black lead to the negative we should see a voltage of around 12.6 volts if it's below 12 then the battery is not functioning properly by the way if you don't already own a multimeter then i'll leave a link in the video description down below for which ones i recommend and from where when we start the car the voltage will drop because the starter motor is pulling a huge amount of current the voltage will drop to around 11 volts if it drops below 10 however then the battery is not functioning properly once the engine is running the alternator should be generating electricity and so we should see a higher voltage of around 14 volts that's because the alternator is recharging the battery and the voltage needs to be higher to help force electrons back in and reverse the chemical reaction 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 or sessions with team members or clients all 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.com forward slash engineering mindset to save 10 of your first purchase of a website or a domain okay guys that's it for this video but to continue learning then check out one of the videos on screen now and i'll catch you there for the next lesson don't forget to follow us on facebook instagram linkedin as well as the engineeringmindset.com

Channel: The Engineering Mindset

Views: 1,288,462

Keywords: car battery charger, car battery, how it works, lead acid battery, alternator, automotive engineering, automotive, generator, how a battery works, diy, engineering explained, auto repair, how to charge a car battery, 5 minute craft, 12v, car maintenance, jump start, electronics, how to, mechanic, maintenance, electrical engineering, electrical wiring, wiring diagram, electrician, current, tutorial, battery charger, electron, house wiring, ohm's law, how does a battery work, tools, audi, dc

Id: VnPRX5zQWLw

Length: 16min 1sec (961 seconds)

Published: Mon Aug 24 2020