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.
Weak Battery Warning Signs
You may have a battery problem if the starter motor cranks the engine slowly or the Battery/Charging warning lamp is illuminated. Another weak battery indicator on older cars is dim incandescent headlights, particularly at idle. However, not every failing battery reveals itself through obvious symptoms.
To avoid being stranded by a battery problem, have the battery inspected at every oil change to make sure the cable connections are clean and tight, and the hold down hardware is secure. Once a battery reaches three years of age, have it tested annually. The test will identify if the battery has deteriorated to the point where replacement is recommended to prevent an unexpected failure. In most areas, members can call the AAA Mobile Battery Service to have a battery tested and replaced (if necessary) at their home or work.
Battery Selection Tips
There is no “one-size-fits-all” battery suitable for every car. The battery type, physical size, terminal configuration, and cold cranking amps (CCA) or amp-hour (Ah) rating are all important factors that ensure the proper fit and function of a battery. Installing an incorrect battery can adversely affect the electrical system of your vehicle, and cause major damage if the terminal locations create a short circuit with nearby components. If you are unsure about which battery to buy, ask your car mechanic or consult the vehicle owner’s manual.
Batteries are either conventional lead-acid or the more advanced AGM design mentioned earlier. Most cars on the road today use conventional batteries, but some models use AGM batteries that are highly spill resistant and better able to handle repeated discharging and recharging, as occurs in cars that have engine stop-start systems to improve fuel economy. Because charging systems are often optimized for the battery type, AAA recommends always replacing a battery with the same type that came in the car from the factory.
The group number, for example Group 24, is an industry standard that defines the battery’s physical size, its hold down configuration, and the type and location of its terminals. Selecting a battery with the same group number as the original equipment battery will ensure a secure fit, adequate clearance, and no cable/terminal issues. It will also allow for proper reinstallation of the important battery heat shield, where equipped.
Some imported vehicles use batteries that conform to European or Asian battery standards. In many cases, a standard group number battery will fit with minor or no modifications, but pay special attention to ensure that the installation does not pose any problems. Application guides are available where batteries are sold, and you can trust AAA’s Mobile Battery Service to install the correct part. In a limited number of cars, the vehicle design makes a factory replacement battery the only viable option.
Cold Cranking Amps Rating
The cold cranking amps rating, for example 650 CCA, is an industry standard measure of how much electrical power a battery can provide at zero degrees Fahrenheit. Never confuse this rating with “cranking amps” (CA), a rating based on an easier test that produces inflated numbers. Some import automakers state battery power requirements using an amp-hour rating, for example 78 Ah. This rating is based on the number of minutes a battery can provide a specified level of electrical current, typically 20 amperes.
To avoid electrical system problems and a visit to the repair shop, never install a battery with a CCA or Ah rating that is lower than that recommended by the vehicle manufacturer. A higher-rated battery will also work if it fits properly, but is usually unnecessary and may have a shorter service life in hot climates.
When your car needs a new battery, always purchase one from a high-volume seller with fresh stock. You do not want a battery that has already lost a good portion of its service life sitting on a shelf. Also, look for a battery with an extended full-replacement warranty. Quality batteries offer free replacement for three or more years if there is a problem within that period. A warranty that enters a pro-rated replacement period sooner will require a partial payment to replace the battery once the full-coverage term expires.
Finding Quality Auto Repair
AAA recommends that you plan ahead for vehicle service by finding an auto repair shop and technician you can trust before you need them. AAA.com/AutoRepair
provides information on nearly 7,000 Approved Auto Repair facilities that have met AAA’s high standards for appearance, technician training and certification, insurance coverage and customer satisfaction. AAA regularly inspects every Approved Auto Repair facility and surveys their customers to ensure ongoing performance. In addition, AAA members receive special benefits that include auto repair discounts, an extended 24-month/24,000-mile parts and labor warranty, and AAA assistance in resolving repair-related issues.