How long do car batteries last?

The short answer: three to five years

AAA puts the normal life of a car battery at three to five years. Where you live makes the biggest difference. In cooler northern climates a battery often lasts five years or more; in hot southern areas, about three years is typical. Consumer Reports, citing AAA data, puts it at 58 months or more in the far northern US and under 41 months in the far south.

That is an average, not a guarantee. A battery can fail in two years or keep going for six or more, depending on how the car is used.

What shortens battery life

Heat

Heat is the biggest enemy. It speeds up the chemical reaction that makes electricity, but it also speeds up wear inside the battery. Under the hood, temperatures can climb past 200°F (about 93°C) in hot weather, according to AAA. Consumer Reports says summer heat is tougher on batteries than winter cold.

Cold

Cold does not wear a battery out as fast as heat, but it is when a tired battery gives up. According to AAA, a battery loses about 35 percent of its strength at 32°F (0°C) and about 60 percent at 0°F (-18°C). At the same time, cold, thick engine oil makes the engine harder to turn. A battery weakened by summer often fails on the first cold morning.

Short trips and parking

Starting the engine takes a big gulp of power. On a short trip the alternator may not have time to replace it, so the battery never fully recharges. Cars parked for weeks also lose charge on their own. A battery that is often run low wears out sooner. AAA suggests a maintenance charger (a "battery tender") for cars that sit unused.

Other factors

• Lots of electrical equipment. Modern cars with many electronics, and cars with stop-start, put more demand on the battery.
• Vibration. A loose battery that is not held down properly can be damaged by vibration.
• Corroded or loose terminals. These stop the battery charging properly.

Signs your battery is dying

• The engine cranks slowly when you start it.
• You hear clicking when you try to start.
• Headlights look dim, especially at idle, or yellow rather than white.
• The horn sounds weak, or electrics like the radio or heated seats act up.
• The battery warning light comes on.
• You have needed more than one jump-start recently.
• The case is swollen, cracked or corroded, or there is a rotten-egg (sulfur) smell. Do not jump-start a battery like this.

If the car will not start at all, our step-by-step guide to jump-starting a car safely will usually get you moving.

How to make your battery last longer

1. Test it every year from year three. AAA recommends an annual test once the battery reaches three years. Consumer Reports' expert suggests starting yearly load tests at two years in a hot climate and four in a cold one. Many parts stores and garages test for free.
2. Keep the terminals clean and tight, and make sure the hold-down clamp is secure. Ask for a check at every oil change.
3. Take a longer drive now and then if you mostly do short trips.
4. Use a maintenance charger if the car is parked for weeks.
5. Turn off lights and accessories before you switch off the engine.

When you replace it

Fit the same type of battery the car came with. Cars with stop-start often use an AGM or EFB battery, and AAA recommends sticking with the original type. Consumer Reports advises buying a battery that is less than six months old, ideally three months or newer, so check the date code. Some newer cars also need the new battery registered with a diagnostic tool. See what to expect in our car battery replacement cost guide.