There is no simple answer to the question of how long a car battery will last, but it is possible to offer some generalizations based on decades of industry experience. To begin with, we know that the life of a car battery varies based on three key factors: time, heat and vibration. Let’s take a closer look at each.
Like people, car batteries age over time and have a finite lifespan. Even in ideal operating conditions, batteries gradually deteriorate until they can no longer provide enough power to start an engine. Automobile usage patterns also contribute to battery aging. Cars driven mostly on short trips may not allow the battery to fully recharge, and batteries in vehicles parked for extended periods naturally self-discharge. In both of these situations, using a maintenance charger like AAA’s Battery Tender will keep the battery fully charged and extend its service life.
Heat facilitates the chemical reaction batteries use to generate electricity, but it also increases the rate of battery degradation. In cooler northern climates, a battery may last five years or longer, but in hot southern locales around three years is more typical. Batteries also live in a harsh underhood environment where temperatures can easily exceed 200 degrees Fahrenheit in hot weather. To combat this heat, automakers may mount the battery in an isolated area, install a heat shield over the battery, or relocate the battery outside the engine compartment, often under the back seat or trunk floor.
The last key factor in battery life is vibration, which causes physical breakdown of internal battery parts. To minimize the effects of vibration, special hold down hardware secures batteries in place and prevents them from moving about. Missing or loose hold downs can significantly shorten battery life.
While less common than the factors above, a malfunctioning charging system will also reduce battery life. Persistent under- or over-charging accelerates battery aging. Some newer cars with absorbent glass mat (AGM) batteries require careful control of charging rates for maximum battery life, and the automaker may even alter the charging strategy as the battery ages. Finally, allowing any car battery to go completely dead will take a big chunk out of its lifespan, even if it can be recharged and put back in service.