 Hello. Good morning friends. Today we are going to discuss the topic automobile electrical system. In that we will see different parts that are already there in the automobile electrical system that we will discuss in detail. Today we are going to discuss the automobile battery in detail. So I am Mr. Anar Thambake, Assistant Professor, Department of Mechanical Engineering, Walsh and Gestalt Technology, Solapur. Learning outcome, at the end of this session students will be able to explain automotive battery for different applications of automobiles. So in this particular session we are going to discuss introduction regarding the automobile battery, then how the battery is going to function, battery components, how the battery is going to work, then how the battery is discharging and charging and the battery testing. So battery is an important component in the auto electrical system. All batteries used in modern automotive applications are of lead acid storage type battery. Different types of batteries are also there but the most common used batteries are the lead acid batteries that are storage type. Essentially a lead acid storage battery is an electro chemical device for storing energy in chemical form. This energy can be released as electricity when connected to an outside circuit. A battery can perform this operation repeatedly that is reversibly. So what is happening over here? So whatever lead acid battery is there whenever it is charging, that time whenever we are using that time it is going to discharge and again with the help of alternator it is going to charge again. So like this way it is performing the operation repeatedly and it is again reused. So next thing is that is the very important part. That is what are the battery functions? So to provide current for the starter and ignition system when cranking. To provide the extra power necessary when the vehicle's electrical load that is radio lights etc. exceeds the supply from the charging system current. To act as a voltage stabilizer or reservoir in the electrical system so that evens out voltage spikes and prevents them from damaging other components in the electrical system. So different body battery components are there that are plate grids, separators, electrolyte, containers, terminals and vent caps etc. The first one is the plate grids and separator. Here positive group and negative group is shown and two volts that are shown that are terminals. So in between there are the separators. So whatever the positive group is there that positive group is formed with the lead oxide that is also called as lead peroxide and the negative group group is formed the material with the help of sponge lead and the separators are required to fit in between for avoiding the short circuit between the positive group and the negative group. So in such a way that the battery grids and separators are fitted in the battery. Next thing is that is very important electrolyte. The mixture of sulphuric acid and water is there that is electrolyte. So ordinarily the electrolyte is used in a fully charged battery contains about 25% sulphuric acid and 75% water. The strength or percentage of the sulphuric acid in the solution is measured by its specific gravity that is the density of the electrolyte versus the density of pure water. The specific gravity or electrolyte strength of fully charged battery is in the range of 1.260 to 1.275. This means that its electrolyte is at least 1.260 times heavier than pure water. Please remember my friends. So containers terminals and windcaps are there. Here two terminals are there that already that we have discussed and in the container the electrolyte is fully filled and there are the windcaps whatever the air bubbles are there. That air bubbles are going to express escape from these particular fans to eliminate whatever the air gap is there in between the container. So according to which this particular container and terminals are fitted into the battery. How battery works? The most important attribute of a lead acid storage battery is its chemical reversibility. That is it operates in a constant process of change and discharge, charge and discharge. When a battery is connected to a load that needs electricity such as the starter in your car. Current flows from the battery. The battery begins to be discharged. In the reverse process it becomes charged when current flows back into it. Through a chemical reaction the batteries achieve chemicals will be restored to a state of charge. Next thing that we are going to discuss is battery charging. Battery discharging. How the battery is going to discharge? Initially the battery is charged and whenever we are going to use this particular energy for different works in the automobile electricity system then it is going to discharge. How it is going to discharge? The discharge process in a battery is begun as soon as an electrical circuit is completed. Such as turning on the vehicle lights. Current flows from the battery through the positive terminal. During the time sulfuric acid works on both the plates at two material. The chemical reactions form lead sulphate on the plates so that liberating water which reduces the concentration of acid in the electrolyte. The amount of acid consumed by the plates is in direct proportion to the amount of energy removed. Next thing is that after discharging how the battery is going to charge? To recharge the battery it is the only necessary to reverse the flow of current provided by the alternator through the positive terminal and out the negative battery terminal. The separate the sulphate that formed on the plates during discharge is changed back to sponge lead and the sulfur returns to the electrolyte forming sulfuric acid again. At the positive plates the lead sulphate changes to lead peroxide again and returns even more sulfuric acid to the electrolyte. In this way the battery is going to charge with the help of alternator. Next thing that how to test the battery? So that is the very important task in this particular discussion. So to determine if the battery is in good condition to determine if the battery is charged to determine if the battery is defective and should be discarded. So different tests are available so three tests are there over here open circuit voltage test is there that is called as OCV test. Second test is that the specific gravity test and last one is there that is the load test. What we are going to do in this particular test that we will going to discuss in detail. Here what you see the circuit diagram over here there is a battery and there is a voltmeter. In this particular test an OCV test is performed with that voltmeter. Turn off all electrical loads and the charging sources from your vehicle. For an accurate reading allow the battery to sit with no electrical loads applied for at least one hour. Connect a voltmeter to the positive and negative terminals and measure the terminal post voltage with no loads or chargers connected to the battery. Voltage less than 12.4 voltage needs this test is performed with a hydro needs the battery to be replaced. So the next thing is that next test that is specific gravity test. What we are going to test over here this test is performed with hydrometer. So percentage of water that we are calculating or we are observing from this particular test. Draw electrolyte into the hydrometer a few times so that the float reaches the same temperature as the electrolyte when you draw the electrolyte make sure that the hydrometer is full. Check each individual battery cell. A reading of 1.265 or greater at 80 degree faraday indicates a full charge 1.11 to 1.14 completely discharged. So in this way the specific gravity test is to be performed and the battery condition is to be noted. Last one is the load test. It measures the terminal voltage while discharging at a high rate. Load is applied using a test tester includes emitter, voltmeter and a resistor. This test is a 15 second discharge of the battery at half cold cranking and ampere level. Depending on temperature it should read the minimum voltage for example 9.6 at 21 degree Celsius. Please make a correction over here that is 21 degree Celsius my dear friends. These are the references repulsing automobile engineering that is by standard publisher automobile mechanics by N.K. Giri automobile electrical equipment by P.S. Coley, K. Newton and W. Seats, T.K. Garrett motor vehicle elsewhere publication. William Suchcrouse this is very important book automotive mechanics that is Tata McGraw Hill publisher publishing house. Thank you.