How do car batteries work?
Although the technology has not changed greatly over the years, the use of the car battery has expanded. The battery provides the necessary burst of electricity to start the car’s engine, sending it down the cable to power the starter motor, which then turns the flywheel. In addition, the battery provides power when the engine is not running. Lights and security systems stay on after the engine has been shut off. On board computers also perform many basic diagnostic functions while the car is not in use. Last and least known, the battery acts as a giant capacitor. It easily absorbs any alternating current (AC) produced by the alternator but not rectified (converted) into direct current (DC). Electrical components need DC to work, but will perform poorly or break down if exposed to AC current. The battery shields these sensitive electrical components.
On average, how often do you need to replace your battery?
Most car batteries will last an average of 4–6 years, depending on the quality of construction and design. As the battery starts the car and provides power when the car is not running, the number of starting cycles or key turns is more instrumental to the longevity of a battery than months or years. Temperature extremes, engine vibration, worn starter motors, and the addition of high-draw aftermarket electronics may also affect the length of useful battery life. Ultimately, the most proactive approach to predicting when to change a battery is to have it load tested when in for other service. A load test will place the battery under similar conditions to how the starter does, where a more accurate measurement of the battery state can be obtained. A battery that falls below 9.5 volts under this dynamic test should be replaced.
What happens if you don’t replace your battery?
If you don’t have your car battery tested regularly, or don’t change it when recommended, there are several consequences. The most painful will be a lack of sufficient power to start the car. Jumping the car with another battery can temporarily resolve the problem, if the bad battery can still accept a charge. If the battery can no longer hold a charge, or if the battery is drained or fully discharged, the alternator may have to work harder to keep up with the power needs of the car and the attempt to recharge the battery. This may cause a failure or shorten the expected life of the alternator. Moreover, if the battery no longer supplies engine-off power to keep alive memory (KAM), stored data will be erased, causing drivability issues (air-fuel ratio calculations, shift points, idle values). In the worst case scenario, key codes can be erased and the anti-theft computer won’t recognize a key. If this happens, you will not be able to start your vehicle until after a reset with an appropriate factory computer is performed and values are restored.
Most automotive service professionals can perform this service. Keep in mind, pricing will vary by location and your vehicle make and model. Use Openbay to compare battery replacement costs with top repair shops in your area.
Service article written by an ASE Master Technician