A 12-volt battery can go from starting the car fine to not starting it at all with little warning. Knowing how long batteries usually last, and what shortens their life, helps you replace one on your own schedule instead of at the side of the road.
How long a car battery lasts
AAA puts the typical life of a car battery at three to five years. Climate makes a big difference: AAA says batteries in hot southern areas often last around three years, while those in cooler northern climates can go five years or longer. Driving habits, how the vehicle is stored and the health of the charging system play a part too.
Heat wears batteries out
Heat speeds up the chemical reaction that produces power, and it also speeds up the battery's decline. AAA notes that under-hood temperatures can top 200°F in hot weather, and heat can lead to fluid evaporation and internal damage. That helps explain why batteries in hot climates tend to wear out sooner.
Cold exposes a weak battery
Cold works from the other direction. A cold battery delivers less power just as the engine needs more to start. According to AAA's Northeast club, a battery at 0°F can supply only about half of its rated capacity, and an engine needs roughly 30 percent more energy to start at freezing. A battery that was borderline in the fall may not be up to the first hard freeze.
Charge level matters in winter too. A fully charged battery is unlikely to freeze, while a completely discharged one can freeze at around 32°F, so don't leave a dead battery sitting in cold weather.
Habits that shorten battery life
- Short trips: the vehicle may not run long enough to fully recharge the battery.
- Long periods parked: batteries slowly self-discharge. A maintenance charger can help a vehicle that sits for long stretches.
- Running it completely dead: a deep discharge takes a sizable chunk out of a battery's life.
- A loose hold-down: vibration breaks down internal parts, so the battery should be held firmly in place.
- Leaving things on: lights, chargers or other accessories left running with the vehicle off can drain the battery.
Warning signs
- The engine cranks slowly when you start it
- Clicking when you try to start the engine
- Headlights that look dim, especially at idle
- Electrical features acting up
- The battery or charging warning light comes on
- You've needed several jump starts lately
- A rotten-egg or sulfur smell near the battery
- A swollen or bulging battery case
A sulfur smell or a swollen case can signal a damaged battery. Don't try to charge or jump-start it; have a professional deal with it.
Get it tested
AAA recommends having the battery inspected at every oil change and tested every year once it reaches its third year. The inspection should confirm the cable connections are clean and tight and the hold-down is secure. Corrosion on the terminals doesn't by itself mean the battery is failing; a proper battery test is what tells you. When it's time for a replacement, have a shop install a battery that matches the type listed in your owner's manual.
Electric vehicles have one too
Electric vehicles run on a large high-voltage battery, but they also use a low-voltage battery for everyday electronics. Mazda explains that in an EV this 12-volt battery powers items such as door locks, windows, infotainment, cameras and control units, and that it controls the relays that start up the high-voltage system. If that small battery is dead, the EV won't power up to drive, however much charge the main pack holds.
The high-voltage battery keeps the small one topped up through a converter, but the small battery can still wear out. Tesla's Model Y manual says earlier vehicles used a lead-acid low-voltage battery and later ones use lithium-ion, and Tesla says the touchscreen will alert you when it needs replacing. Tesla also notes that a Model Y can't be used to jump-start another vehicle. Check your EV's owner's manual for its jump-start points and steps.
Battery care checklist
- Note your battery's age and plan on a yearly test after year three.
- Ask for a battery inspection at each oil change.
- Keep the connections clean and tight and the hold-down secure.
- Use a maintenance charger if the vehicle sits for long periods.
- Watch for slow cranking, dim lights or a battery warning light.
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