The battery is often at the root of most starting problems. A battery is the prime producer of electric current that also powers various transitional components in the electrical circuit, right from ignition and starter systems to luxury accessories. Ignition circuit factors like the enhancement of battery current which is necessary when a vehicle has to start in changing conditions, the flow of current in the circuit through intermediate links like the coil resistor, contact breakers, condenser and finally the spark plug, should be considered collectively when a vehicle breaks down. Without these considerations one's evaluation of a battery and its applications would remain incomplete.

Battery current is distributed into several channels through the ignition system where it is enhanced as per need. On its own a battery current is not enough to produce the necessary spark for ignition. Enhancement of the voltage is necessary to produce a spark capable of igniting the air-fuel mixture in the combustion chamber at the most optimum time.

BATTERY CURRENT FLOW TO IGNITION COIL:
An ignition coil steps up the voltage provided by a battery. It is a dually wound coil enclosing a primary winding of thick copper wire and is connected to the battery through an ignition switch and contact breakers. There is a secondary winding with many more turns of thinner gauge of copper wire connected to the spark plugs through the distributor. The primary winding is placed within the secondary winding, ensuring no contact between the two. Consequently, the primary circuit is formed by the primary coil, ignition switch and contact breakers and the secondary circuit is formed by the secondary winding, distributor and spark plugs. The boosting of the current takes place within the ignition coil when the ignition switch is turned on and the flow commences. Current entering the coil in regular flow, first runs into the primary winding of the coil via the ballast resistor which regulates the current flow. When the ignition switch is turned on, the current bypasses the resistor (in cold start conditions) so that a substantial amount of current enters the primary circuit. A ballast resistor is installed in series with the primary winding to regulate the current entering the primary circuit and to also lengthen the life of the contact breaker points.

The current having entered the primary circuit creates a magnetic field around the winding. Meanwhile a cam mounted on the camshaft, passes through the body of the distributor assembly actuating the opening and closing of the contact breaker points annexed to the distributor base plate. Current flowing through the primary circuit of the coil breaks as the contact breaker points open. As soon as the flow of current in the primary winding is obstructed a voltage surge is realised in the primary as well as secondary circuit. The voltage surge in the primary circuit forms a shield against a new current flow into the circuit because, if there is an immediate flow of current in the circuit the magnetic field collapses and the voltage concentration needed in the secondary winding is not met. The continued flow of electric current in the windings tends to jump from one point to the other which can be seen as an arc across the contact breakers. Consistent current jumping defaces the contact breaker points eventually obstructing optimum conduction of current and necessitating their replacement.

IGNITION COIL - DISTRIBUTOR - SPARK PLUGS:
The enhanced voltage is transferred further to the distributor through a High Tension (HT) coil wire. A distributor delegates the enhanced coil voltage to the respective spark plugs. It forms a casing for the contact breakers and the ignition advance mechanism to adapt to varied load and speed conditions. A gear mounted on one end of the cam mounted shaft meshes with the gear on the cam shaft to generate the same speed as the cam shaft. The cam end holds a rotor instrumental in distributing the coil current to the spark plugs by rotational motion.

CONTACT BREAKER POINTS:
The contact breakers break the current flow in the primary circuit so that voltage is induced in the secondary winding of the ignition coil. The contact surfaces of breaker points are made of conductible metal that continue in a strip of spring steel. One strip moulded with a face of the point is fixed to the base plate of the distributor as earth. This part of the breaker is also used to adjust the dwell angle between the two points. The spring steel strip is insulated from the distributor body and is also in contact with the cam lobes through a plastic projection. The plastic insulation undulates as it comes in contact with the cam lobe on the rotating shaft.

IGNITION ADVANCE SYSTEMS:
The spark advance system deliberates a spark to the air fuel mixture in the engine cylinder under varying load and speed conditions. There are two types of ignition advance systems - Centrifugal spark advance mechanism and Vacuum Advance mechanism. The centrifugal ignition advance system responds to the engine speed while the vacuum advance system responds to the vacuum created in the engine cylinder. In the centrifugal advance system, two steel weights are attached to the revolving plate based at the bottom end of the distributor assembly. The spring loaded weights are pivoted on the base plate and revolve with the rotating shaft. As the shaft rotates the weights are flung open due to centrifugal force and in turn twist the contact breaker cam forward so that the points open earlier and the spark plugs fire in direct proportion to the shaft speed.

The vacuum advance system functions in accordance with the vacuum created in the engine cylinder. A narrow pipe runs from the manifold to the vacuum chamber on the distributor. A diaphragm on the inside of the vacuum chamber is pulled when vacuum increases. This twists the contact breaker plate slightly, advancing the motion of the breakers to open quicker.