Q: How long should a car battery last?
That’s an excellent question, but a difficult one to answer. “I’ve seen batteries in desert climates fail in two years, and I’ve seen a battery that was 10 years old and still working fine,” says Matthew Manke, AAA’s supervisor of emergency road service training. “A variety of factors affect a battery’s performance and lifespan.”
In the old days, a battery’s primary function was to start the engine. But now that cars have become loaded to their rooftops with vast numbers of electronic doodads, the battery also has to work hard to keep all this stuff functioning.
Even when the engine isn’t running and the alternator isn’t charging the battery, it must keep things like the radio presets and the security alarm operational. And many new cars come with a fuel-saving start-stop feature that causes the engine to automatically turn off and restart perhaps dozens of times during a single trip, relying on the battery each time.
Fortunately, batteries have improved since the days when they needed periodic topping-off with distilled water. Today, a battery is typically “maintenance-free”—sealed and meant to retain its electrolyte solution for its lifetime. And now there’s an alternative to the traditional lead-acid battery. AGM (absorbed glass mat) batteries are coming as original equipment on many new cars. They’re generally more robust, although they’re also more costly.
A car battery must be kept well charged. Not only will this ensure that the car starts when you need it to, but the battery will have a longer life span. Following are some things that can cause excessive drain and shorten battery life.
A malfunction (a stuck fuel-pump relay, for example) or an electronic device, such as a cell phone, left plugged into an “always on” power receptacle overnight.
Undercharging from, say, a faulty alternator or too many short trips that don’t give the alternator time to recharge the battery.
Summer heat of 100-plus degrees, which increases a battery’s internal discharge. Extreme cold also negatively affects battery chemistry.
A battery will slowly drain and eventually die during a long period of inactivity. If you drive your car infrequently, a “battery tender” that monitors the state of charge and recharges the battery when necessary is a good investment, says Manke. They’re available from various retailers, auto-parts stores, and online.
If your car’s battery is three to four years old, have it professionally tested. If it can no longer hold a proper charge, be sure to buy a replacement battery that’s the correct fit and matches or exceeds the cold-cranking amps and reserve-capacity ratings of the original.
Think twice before installing the replacement yourself, because disconnecting the battery without providing an alternative power source can create havoc in modern cars. The absence of battery-supplied voltage erases the memories of modules that control the transmission, antilock brakes, and other components. If you disconnect the old battery, your vehicle might need diagnostic scanning and reprogramming.
And beware of jump-starting a car that has a dead battery. “Electronic systems on modern vehicles are at risk of damage from electrical surges and voltage spikes, and jump-starting adds to the risk,” says John Latner, AC Delco technical training manager. It’s much better to have a professional handle such matters. One option for members: The AAA Battery Service can come to your car, diagnose the problem, and, if necessary, install a new battery.
Photo (top): Art Directors & TRIP / Alamy Stock Photo