5 Reasons Car Batteries Die

5 Reasons Car Batteries Die

"If your car battery keeps dying, it's probably due to one of these five fixable issues. "

Last Updated May 8, 2024 | Meghan Drummond
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Few things are as frustrating as a dead, or dying, car battery. When it's working correctly, the battery should start the engine and then be recharged by the alternator while you drive. A bad battery means that your car can't start, which can be frustrating, especially if you don't know what caused it to die.

What Causes Car Batteries to Die?

The five most common causes of a dead car battery are: cold weather, battery age, corrosion, electronic battery drains, and parasitic battery drains.

If you're struggling with a battery that seemingly can't hold a charge, these are the five things to check first and what you can do about each of them. The last two are closely related, but while one can be controlled the other is harder to detect. Read about the most common dead car battery causes below to find out why your battery keeps dying and how to prevent it from losing its charge.

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Cold Weather Can Cause Your Car Battery To Die

Cold weather is the number one reason why car batteries die. Weather doesn’t have to be particularly extreme to cause a car’s battery to weaken. Even at a mild 32 degrees, most car batteries can become 35% weaker. At 0 degrees, a car battery’s effectiveness plummets to 40%. When a battery is that weak even powering your interior lights can become a challenge, let alone starting your car. There's a reason most people associate dead car batteries with winter, and that's because it's when most batteries that were in marginal condition give up and die.

This one can be hard to fix. Obviously, you can't change the weather, and not everyone has easy access to a parking garage or carport. Really, the only thing you can do is be aware that your battery is more likely to die during winter and make the required preparations.

Keep an eye out for symptoms that your battery may be losing steam. If you notice your headlights dimming while your car idles or hear a strange clicking sound when you start your vehicle, that's a good indicator that your battery is on its last legs. To affirm that it's getting close to its last start, you can either test the battery yourself or go to a nearby auto shop where they'll be able to test your battery for you. Many states require this as part of the inspection process as well, which is a good time to make note of your battery's expected life.

You can’t change the weather, but you can prepare for the worst.

An orange S550 Mustang in the snow

Car Batteries Die Over Time

Time, not surprisingly, is also a top reason why car batteries die. Just like the batteries in your remote, eventually, there is just no juice left and no amount of jumping will bring your battery back to life. The average car battery dies after three to five years, though newer batteries have gotten better at extending their lifespans. Car batteries have a shorter lifespan if you’re in an area prone to especially cold winters. Be sure to keep an eye on how many years of use your car’s battery has, and look for the warning signs of battery failure. Don’t forget to test your battery regularly.

The other way time affects car batteries is "time unused." The longer you go in between drives, the less likely your car is to start up. Car batteries are charged by the alternator, which only turns if the car is running. If you’re not able to drive your car for a while, it’s worthwhile to invest in a battery tender. Battery tenders act as a charging system for your battery, making sure it stays fully charged without overcharging.

Much like cold weather, time isn't something you can actually change. But by keeping track of it and being observant, you can be prepared for the worst and reduce the chances of you car’s battery dying while you're unprepared.

Corrosion Can Cause Your Car Battery To Die

Battery acid is corrosive. That might sound obvious, but one of the main reasons why car batteries die repeatedly is due to corrosion at the negative and positive terminals. The battery terminals are the points of contact on the top of your battery, one is marked with a positive charge symbol, the other a negative. These are the points that you use to jump your car, and they're also the way your battery is able to be charged by your alternator. If your battery’s connection is corroded, your alternator may not be doing an adequate job of recharging your battery.

If you see blue or green growths hanging off your battery terminals, that’s a sure sign that your battery has been damaged by corrosion. Corrosion can also look like a thin white powdery substance, almost as if your battery has a bad case of dandruff. Though this is a perfectly natural and expected process, it isn’t doing your battery any favors and by improving the connection you can improve your car’s ability to charge the battery.

If there isn't much corrosion, you can use a dry rag to wipe away dirt and grime. If that doesn't do the trick then use a stiff wire brush to clean the corrosive material. With a little effort, your battery will have a cleaner contact surface and an easier time charging.

hands use a wire brush to scrub corrosion from a car battery

Leaving Electronics On Can Cause a Dead Car Battery

We've all accidentally left our headlights on and killed our car’s battery. It's practically a right of passage. And that's one of the many reasons why human error is a top cause of dead car batteries. Everyone makes mistakes that can lead to a dead car battery.

One of the more common mistakes we make is forgetting exactly how much we've started expecting batteries to do. Car batteries are really pretty amazing. They power everything in the car, and over time that’s expanded into digital navigation systems and displays. Add to that people charging their phones, tablets, computers, and mobile entertainment centers on the go and you have a very overtaxed battery system.

This isn't an easy one to fix. Obviously, you can firmly resolve to always turn your headlights off when you leave the vehicle, but it's not like anyone intends to forget something. Even if you do a perfect job of unplugging your devices and turning off your headlights, the car battery doesn’t actually get a break. Instead, it’s hard at work powering the anti-theft system and keeping the time on your clock.

Make sure to give your car a break when you can by unplugging your charging cables at home. Also, obviously, make sure that your lights are off when you turn the car off. Just changing your parking angle so that you can see the headlights from your front door can make a big difference in how easy it is to forget to turn off your lights.

Electronic Parasites Can Cause a Dead Car Battery

Electronic parasites are electrical components that can drain your battery over time due to decreased functionality or faulty wiring. While these electrical problems can be addressed, they aren’t as predictable as the other reasons car batteries die. One of the most frequent parasites is a bad alternator. Your battery relies on your alternator in order to recharge. If the alternator isn’t pulling its weight, your battery may die frequently even when you know the weather is lovely and you haven’t been draining the battery. Sometimes a broken fuse can drain a battery, even when your car is off. For electrical problems, you’ll want to get a skilled mechanic involved. Though the voltage produced by a car battery isn’t enough to kill a person, there are other hidden dangers that can pose a threat to your safety if you don’t know what you’re doing.

A red and black cable are used to test the car battery

How To Jump a Dead Car Battery

Ultimately, the best thing you can do to help yourself deal with the probability of an eventual dead battery is to be prepared. Portable jumpstart units are inexpensive and can be a lifesaver in unexpectedly cold weather. Jumper cables, of course, are the old standby and they work fantastically. Keep them in a cable bag in your trunk and relax a little with that piece of mind.

Jumping a car is easy. With both vehicles in park or neutral, attach the cables in the following sequence: Red Bad, Red Good, Black Good, and then ground the remaining cable on any unpainted metal surface in your car. To elaborate a bit, you attach the red cable to the bad battery, then attach the red cable to the good battery, and then attach the black cable to the negative terminal of the good battery. Attach the last clip to any unpainted metal surface. A lot of people go for the struts, which is a good choice. Then turn on the good car. When it's been running for a couple of minutes, try to turn on the car with the dead battery. It should turn on immediately, if it doesn't, give it another five minutes and then try again. If that doesn't do it, you may need a new battery.

Just make sure that after jumping your car you drive it for a while before powering it off. That will give the alternator time to recharge your car’s battery.

Take care of your car’s battery, prepare for the worst, and stay safe out there.

This article was researched, written, edited, and reviewed following the steps outlined in our editorial process. Learn more about CJ's editorial standards and guidelines.