The normal life expectancy of a car battery is typically estimated at four years when it operates under normal conditions. This means that the battery does not operate under extreme temperatures, is submitted to a full charge cycle and is not used to power excessive accessories.
This normal lifetime projection is tested under ideal conditions and rarely translates accurately to real-life conditions. Increasing numbers of standard car accessories, such as MP3 players and GPS devices, and driving style can reduce a car battery's life expectancy. A driver with a short commute, for example, rarely travels far enough for the car battery to charge fully.