Battery Ignition System/ Coil Ignition System Working, Advantages and Disadvantages

Read: Battery ignition system construction and essential components

The main components of a battery ignition system are battery, ignition switch, ballast resistor, ignition coil, contact breaker, capacitor, distributor and spark plug. The source of high voltage/energy for the spark plug is the ignition coil, hence it is also called ignition coil system. Following figure shows a diagram of a conventional battery ignition system.

Operations of battery ignition system

Battery is the primary energy source for the system. One end of the battery is grounded to engine frame. The other end is connected to the primary terminal of the ignition coil through ballast and ignition switch. The ignition switch is the main key to complete the electric circuit in the primary terminal of the ignition coil. The ballast is a special resistor which connected in series to the primary coils. The function of ballast to protect the coil from excessive current. When current increase the ballast resistor get heat and then get higher resistance. Which eventually reduce the current flow through the primary circuit.

The ignition coil consists of secondary coil of large number turns, it wound around over iron core. The primary coil has a few number coil and it is wound over the secondary coil. The entire coil is assembled to a compact unit. Low voltage (12 volts) current from the battery is stepped up to high voltage (10,000 volts) in the ignition coil by the principle of electromagnetic induction. The primary circuit is completed by earthling the other end of the primary coil to the engine frame through the contact breaker. The contact point of the contact breaker is held together by the spring load. The contact opens/ close according to the engine movement by using a camshaft. A capacitor is connected parallel to the contact breaker. Ignition capacitor stores the current induced in primary winding when the circuit become open. It protects the contact points.

One end of secondary coil is also grounded through contact breaker. The other end is connected to distributor. The distributor rotation switch which distributes the high voltage current to the different spark plug according to the firing order of the engine. The spark plug consists two electrodes, one is grounded and the other one is connected to distributor. This results in a large voltage difference between these electrodes and creates a spark across them. The spark is then ignites air-fuel mixture inside the combustion chamber.

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Advantages and disadvantages of battery ignition system

Advantages of battery ignition

1. Initial cost of the battery ignition system is very low.
2. Battery ignition gives a good spark at staring and at low speed of engine.
3. The driving of high-speed engine is simpler than in case of a magneto system.
4. The periodical maintenance required is negligible except for the battery.
5. Since there are no moving parts to generate the current, item requiring attention can be placed to a more accessible position.
6. The adjustment of spark timing has no significant effect over the complete ignition timing range.

Limitations of battery ignition

1. Sparking voltage drop at high-speed operation of the engine, due to the limitation of current switching capability. The stored energy on the coil decreases at high speed due to decrease in time available for building up the current in the primary coil.
2. Since it requires a heavy battery the whole system is bulky.
3. If the battery runs down (low battery), it fails to operate the induction coils and the engine cannot start.
4. Battery is an unreliable part of this system, it requires regular attention.
5. The breaker point’s continuously subjected to mechanical as well as electrical wear.