Most of SI engine used battery ignition system. In this system a 6 volt or 12 volt battery used to produce spark. Passenger cars, light truck, motorcycles and large stationary engines are fitted with this system. Main Parts of battery ignition system: Battery A battery is used to provide energy for ignition. It is work as storage of energy and charged by dynamo, which is driven by engine. It converts chemical energy to electric energy. Ignition switch It is used to turn on and off the ignition system. Battery is connected to the primary winding of ignition coil by ignition switch and ballast resistor. Ballast resistor It is connected in series with primary winding to regulate current in primary winding. It is used to prevent injury due to overheating of ignition coil. It controls the current passes through primary winding. It is made by iron. Iron has property of increase electrical resistance rapidly by increase in tempera