Automotive batteries are the backbone of an automotive electrical system. These devices provide power for start-up, offer a grounding point for the vehicle chassis and can serve as a power source for a short time if alternator failure occurs. Because an automotive battery plays such a critical role in vehicle operations, it is important to know when a battery should be replaced.
Causes and Symptoms of a Failing Battery
An automotive battery is designed to last for a few years; however, a battery that has been exposed to excessive heat or extreme cold may fail prematurely. A battery subjected to improper charging procedures also may be prone to premature failure.
A battery that requires replacement often will fail to start the automobile. This symptom is easily recognisable--the starter motor, which is operated by the battery, will not turn the engine fast enough to start. The battery also may fail to turn the starter motor at all, instead causing the motor to make a clicking sound. Automobiles equipped with a voltage meter on the instrument panel often will show the voltage reading in the red zone (less than 12 V) when the vehicle is switched on but not started.
In rare cases, a battery may have an internal short-circuit. When this happens, the battery may overheat or swell. A battery in this condition should be replaced immediately.
Situations in Which a Battery Does Not Require Replacement
There are some occasions when a battery seems as though it requires replacement but actually requires service.
A loose battery cable may make an automotive electrical system intermittently behave as if the battery needs replacement. To correct this condition, simply tighten the bolt holding the battery terminal to the battery post.
Corrosion around the battery cables, terminals or posts will cause a bad electrical connection. Metal oxidisation affects the electrical conductivity of the metal parts of the battery cable, so it is important to keep these parts as free of oxidisation (in the form of green or white "rust") as possible. To correct this condition, clean the affected parts with a mixture of baking soda and water, rinse the parts and dry them. Rub a small amount of petroleum jelly or grease on the cleaned parts to prevent future oxidisation.
Some lead-acid batteries require periodic maintenance by filling the cells with distilled water. A battery that is in need of water will fail to provide the necessary power to start a vehicle. To remedy this problem, check the cells to see if water is required, and add water as necessary.