In theory, the life of a car battery is determined by a variety of factors, many of which rarely come to full fruition. Under normal circumstances, a car battery has a lifespan of about four years. For a car battery to make it to this average life, it’s under the assumption that it is under the following conditions:
Goes through full charge cycles
Does not get subjected to extreme cold or heat
Connected to a reliable charging system
Does not power accessories
Most automotive batteries don’t live in these “normal” or “ideal” circumstances. In reality, batteries are subjected to temperature extremes in the winter and summer months. Starting your car takes a large surge of electricity from the battery, which means the charging system then kicks in to replenish it. Short trips often mean that the battery does not receive a full charge.
Accessories that rely on the car battery for power can also shorten the lifespan of the battery, as it requires more juice to power items such as phones, MP3 players, and GPS Units, on top of providing power for the vehicle itself.