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. 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 but 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. What you don't want is to have a bad battery!!