H.T coil converts the electrical energy from the car battery to high voltage using two coils, one inside the other, then temporarily stores it before releasing it as a high voltage current pulse to the spark plug. A spark coil, sometimes referred to as an ignition coil, is an induction coil found in your car's ignition system that converts the battery's low voltage into the thousands of volts required to spark the fuel in the spark plugs. H.T coil is used to carry high-voltage power. It travels from the secondary winding of the coil to the plugs via the distributor.