A car battery is an energy storage device that relies on a chemical reaction within the battery to produce electricity. The stored electrical energy is used to initially operate the starter motor, ignition system, and fuel system on your vehicle. Once your car engine is running, the alternator supplies the electricity needed for all vehicle systems and charges the battery to replace the electric energy used when starting a car. Most electric vehicles have a traction battery which is in addition to the standard 12-volt battery that is used to start the car engine. Traction batteries also convert chemical energy to supply electrical energy but operate at higher voltages and often are monitored by the PCM (Powertrain Control Module).
A temporary power source might be installed to avoid the possibility of losing radio presets or stored data in the PCM while the battery is out. When the battery is already completely dead, this step is unnecessary. The vehicle’s negative cable is removed from the battery, followed by the positive cable. The battery tie down system is loosened and the old battery removed. Cable ends and wiring are carefully inspected to ensure cleanliness and no corrosion. In some cases, corrosion can be extreme and the cable may need to be replaced or wiring repaired. The new battery is installed and the tie down system is reinstalled. Anti-corrosion compound is applied to the battery terminals. The positive terminal is reconnected followed by the negative terminal. Some vehicles, for example some models of BMW, VW, and Audi, may require PCM programming to input battery parameters. This step, performed using a specialized scan tool, is necessary to maximize battery life and prevent electrical system malfunctions. The car is started and charging system output is measured and compared against the factory OEM specification to ensure that the new battery will properly recharge. Generally, charging output will be in the range of 13.8 to 14.8 volts but the exact specifications vary by make and model.
Yes, but if you have a weak battery you might be left stranded somewhere if the battery dies completely and you cannot start your car. A faulty battery may also needlessly overload the alternator and could adversely affect the operation of the vehicle’s electrical system, including the vehicle security system and the shift interlock.