Q: How Does a Battery Work With a Car's Electrical System?

asked by on November 30, 2015

How does a battery work with a car's electrical system?

One of the most recognized mechanical parts under the hood of any vehicle is the battery. Whether you’re an ASE certified master mechanic or have never turned a wrench, everybody can pinpoint the location of their vehicle’s battery. Although most car, truck, and SUV owners know what a battery is, most may not be aware of how the battery works with the car’s electrical system to power multiple components that must work together efficiently in order to allow us to drive from point "A" to point "B" every day.

The battery is the primary source of energy that powers virtually all of the electrically charged components on a vehicle. Some of these components include:

  • Headlights
  • Starter
  • Heater / AC
  • Auxiliary systems (radios, alarm systems)

The battery of a car serves two main purposes: starting the car and powering the accessories while the engine is not running. Once the engine starts, the alternator (which is powered by a belt drive) takes over to power all of the vehicles accessories and electrical systems. At this point, the battery converts from power supplier to power generator and self-charges to maintain a level of amps and volts that will permit the battery to have enough power to engage the starter and start the motor once again.

The battery wears out over a period of time. This is due to the metal cells inside the battery and the acid/water inside the battery’s case losing their ability to generate electrons that helps the battery recharge. The battery will also lose a charge when the driver has electrical components left on without the engine running or if the alternator is damaged. When the car isn’t running or the alternator is damaged, the battery will bear the load of powering all of the electrical systems that need power.

Under normal operating conditions, a car battery should last anywhere from 3 to 5 years in most cases. Extreme weather conditions (both hot and cold), along with the driving habits of the car owner can reduce the lifespan of a battery.

The best way to avoid battery issues is to stay on top of routine maintenance, including having your battery inspected once per year by a local ASE certified mechanic. You can also avoid many battery-related problems by having a professional mechanic inspect or replace the alternator on your vehicle before it causes too much damage to your car’s battery.

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