What shortens battery life
- Heat. High temperatures speed up the chemical wear inside the battery. Summer heat often does the damage; the first cold morning is when you find out.
- Short trips. Starting the engine takes a lot of charge, and a short drive doesn’t put it all back.
- Sitting unused. Modern cars draw a little power even when off. A car parked for weeks can drain its battery.
- Accessories left on, and electrical faults that drain the battery overnight.
- Loose or corroded terminals, which stop the battery charging properly.
Signs your battery is getting weak
- The engine cranks slowly, especially on cold mornings
- Dim headlights or interior lights when starting
- The battery or charging warning light comes on
- Electrical glitches, or warning messages after starting
- A swollen battery case, leaks, or heavy corrosion on the terminals
- The battery is more than about three years old and has never been tested
A battery warning light while driving can mean a charging system problem rather than the battery itself. Have it checked soon.
Testing and replacing
A proper battery test measures how well it holds a charge under load — a voltmeter reading alone can look fine on a failing battery. Many parts stores and shops test batteries free.
When replacing, match the size and type your manual specifies. Cars with start-stop systems often need an AGM or similar battery, and some newer cars need the new battery registered with the car’s computer so it charges correctly. Recycle the old battery — the store you buy from will usually take it.
The battery’s age is often printed on a sticker or stamped on the case. Note the install date in your records so you know when it’s getting old.
Common questions
Can a dead battery be recharged?
Often, yes, if it was drained by lights left on. A battery that keeps going flat, or that is old, usually needs replacing. Have it tested after recharging.
How do I keep a battery healthy if I rarely drive?
Take a longer drive regularly rather than only short trips, or use a battery maintainer if the car will sit for weeks.
Does cold weather kill car batteries?
Cold reduces the power a battery can deliver, so a weak battery often fails on the first cold morning. The damage that weakened it is often done by summer heat.