How to Tell If Your Car Battery Is Dying
Car batteries often fail without much warning, usually on a cold morning. Here are the warning signs of a dying battery, how to test it, how long batteries last, and how to jump-start a car safely.
By Pond.com editors Updated 3 min read
Quick answer
- Warning signs include a slow, labored engine crank, dim headlights, a battery or check-engine warning light, and electrical problems.
- Corrosion on the terminals or a swollen battery case are also signs of trouble.
- Most car batteries last about 3 to 5 years, less in very hot or very cold climates.
- A fully charged battery reads about 12.6 volts with the engine off. Below about 12.2 volts it's low and needs charging or testing.
- Many auto parts stores test batteries for free.
Car batteries rarely give much notice before they fail, and they usually choose a cold morning when you're running late. Knowing the warning signs, and testing an older battery before winter, can save you from being stranded.
Warning signs of a dying battery
- Slow, labored cranking: the engine turns over sluggishly before starting.
- Clicking when you turn the key or press the start button, with no crank.
- Dim headlights or interior lights, especially when starting.
- A battery or check-engine warning light on the dashboard.
- Electrical problems: power windows, radio or other accessories acting up.
- Corrosion: white, blue or green crusty build-up on the terminals.
- A swollen or cracked battery case, or a rotten-egg smell. Replace the battery promptly.
- Age: if your battery is more than 3 to 5 years old, it's living on borrowed time.
How long car batteries last
Most car batteries last about 3 to 5 years. Heat shortens battery life the most, while cold weather exposes weak batteries. Short trips, long periods of sitting and leaving lights on can also wear a battery out faster.
How to test your battery
At a shop: many auto parts stores and repair shops test batteries for free. A load test shows how well the battery holds up under demand, which is the most reliable check.
At home with a multimeter: set it to DC volts and touch the red lead to the positive (+) terminal and the black lead to the negative (−) terminal, with the engine off for a few hours.
| Reading | What it means |
|---|---|
| About 12.6 volts or more | Fully charged |
| About 12.4 volts | About 75% charged |
| About 12.2 volts | About 50% charged; charge it and retest |
| Below 12.0 volts | Discharged; it may be failing |
A battery that reads well but still struggles to start the car may fail a load test.
Battery or alternator?
The alternator charges the battery while you drive. If your car starts after a jump but dies again soon after, or the battery warning light comes on while driving, the alternator may be the problem. A shop can test both.
How to jump-start a car safely
- Park the working car close, without the cars touching, and turn both off.
- Connect red to the dead battery's positive (+) terminal.
- Connect the other red to the good battery's positive (+).
- Connect black to the good battery's negative (−).
- Connect the last black clamp to bare, unpainted metal on the dead car's engine, away from the battery.
- Start the working car, let it run a few minutes, then try starting the dead car.
- Remove the cables in reverse order, and drive for at least 20 to 30 minutes to recharge.
A portable jump starter is a handy alternative that doesn't need a second car. Many car insurance policies and motor clubs also offer roadside assistance that covers jump-starts.
Replacing a battery
A new car battery typically costs from around $100 to $300 or more, depending on the car and battery type. Match the size, type and cold-cranking amps (CCA) in your owner's manual. Most auto parts stores will recycle your old battery, which is required in many states.
Common questions
Typically about 3 to 5 years. Hot climates shorten battery life the most, while cold weather exposes weak batteries because it takes more power to start the engine.
Use a multimeter set to DC volts. With the engine off for a few hours, a healthy, fully charged battery reads about 12.6 volts. Around 12.4 volts is about three-quarters charged, and below about 12.2 volts it's low. A shop load test is more reliable.
If the car starts after a jump but dies again soon, or the battery warning light comes on while you're driving, the alternator may not be charging the battery. A shop can test both.
Cold slows the chemical reaction that makes power, so the battery delivers less, while thick cold oil makes the engine harder to turn. A weak battery that worked in summer often fails on the first cold morning.
Yes. Modern cars draw a small amount of power even when off. If a car sits for a few weeks, the battery can drain. Driving regularly, or using a battery maintainer, helps.