|KYLE’S CORNER – AUTO REPAIR HELP|
BATTERY, STARTER, and SOLENOID
Batteries are rated in Cold Cranking Amps, commonly refered to as “CCA”. This rating refers to the amount of amperage the battery can deliver and still provide adequate cranking performance to start the vehicle. The vehicle manufacturer determines the necessary CCA rating required for the vehicle. A replacement battery must meed or exceed this rating in order to operate properly and maintain a satisfactory life expectancy. Battery life can be affected by many factors. Batteries that operate in extremely cold wheather conditions will usually not last as long as a battery operating in moderate temperature conditions. During the continual discharge and recharge of the battery the water or “electrolyte” in a battery can evaporate in the form of a gas. This water should be checked and replenished on a regualar basis. Older style batteries had removable cell covers that allowed the refilling of the individual cells. Newer “maintenance free” batteries have non-removeable covers and special vents that do not require regular service or refilling of the cells. A clean battery can go a long way in improving battery life. Dirt and acid that can collect on the top of the battery can slowly discharge the battery. A properly tuned engine that starts quickly without excessive cranking time will also improve battery life.
STARTER AND SOLENOID
A starter consumes more current than any other electrical device used on a vehicle. In order to ensure an adequate supply of current to the starter, large cables are used to connect the starter to its power source. Voltage is supplied to the starter from the battery through either a remote relay or a starter mounted solenoid. The design of the starter power source depends on the type of drive used. Starters with a Bendix type of starter drive, will typically use a remote starter relay to actuate the starter. This is because the starter drive will extend automatically with the rotation of the starter. It uses centrifugal force to extend the drive and the drive is retracted by the spinning motion of the flywheel after the engine starts. Starters that use a mounted or integral solenoid use the solenoid to mechanically extend the starter drive and close the circuit that supplies current to the starter. The starter drive used on this system is an overrunning clutch type drive. This type of drive spins free in one direction and locks in the other. This action allows the starter drive to spin the flywheel, when engaged, and spin free when the engine starts. The starter drive is withdrawn when the ignition key is returned to the run position.
The solenoid that is mounted on the starter is an electro-magnetic device. When current is supplied to the starter solenoid, by the ignition switch, the solenoid core becomes magnetized causing a plunger to move inside the starter. The amperage require to operate the solenoid is more than is required to hold the plunger in. This is called a peak and hold circuit and is typical of most solenoid operation. The plunger extends the starter drive while closing contacts of an internal switch that supplies battery voltage to the starter. The remote mounted starter relay operates in a similar fashion, but its function is to supply battery voltage to the starter only.
Because a starter requires a large supply of current, typically about 150 to 200 amps, an adequate power supply is needed to ensure proper starter operation. Battery voltage should remain at or near 9.5 volts when cranking. The difference between voltage measured at the battery and voltage measured at the starter, when cranking, should not exceed .5 volts. This difference is called voltage drop, and is an indication of starter circuit resistance. High starter circuit resistance and/or low cranking voltage can cause shortened starter life.
(Kyle has an affinity for Pale Ale and tooling on his 1956 Chevrolet Nomad Station Wagon.)