Your vehicle's radio and headlights, plus a slew of other important functions, are powered by an electrical current generated by your vehicle’s engine. A vital part of generating electricity is having a place to store it while it’s not being used, which is where a car battery comes into play. The battery holds electrical energy while a car is off in order to help the engine turn over and create a spark to start internal combustion. Without a working battery, your car will not be able to start. If you perform proper maintenance, however, an average car battery can start your car reliably for roughly four years.