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How Does Cold Weather Kill a Car Battery?

A snowy road in winter.

It’s not uncommon when the weather turns frigid for people to head out to their cars only to find that the battery is dead. While this can happen at any time of year, it’s more common during the winter when temperatures drop. But how does cold weather kill a car battery? Here are the details of the process and what you can do to prevent an unpleasant surprise when you head out first thing in the morning.

How Does the Battery Work?

Knowing how a battery works is key to understanding how cold weather can kill a car battery. Lead-acid batteries are the most common battery type. They have a plastic case that surrounds lead plates. Each pair of those plates is called a cell. The lead plates sit in a solution that’s a mix of water and sulfuric acid.

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The lead plates store a charge through a chemical reaction between the metal and the surrounding solution. That reaction causes a build-up of lead sulfate, which gradually reduces the maximum charge that the battery can hold. Lead-acid batteries also naturally discharge over time. This gradual reduction — or the battery sitting unused for too long — can result in a lack of fresh charge and would eventually cause every battery to die or become so weak that it wouldn’t be able to start your car.

Why Do Batteries Fail in the Cold?

Extreme temperatures can increase the rate of the gradual discharge described above. Summer causes the water to evaporate, while winter slows chemical reactions. Neither is good for your battery’s life, but the extra challenge in cold weather is the additional power demands of a cold engine.

The oil in the engine is thicker when it’s cold, and it offers more resistance against forces trying to move it around. Extra power is also required to run accessories like defrosters and fans for the heat, which puts your battery under added stress. This is how you end up with an already dead or quickly dying battery on winter mornings.

How to Keep Your Battery from Failing

Every battery eventually fails, but you can take steps to prolong your car battery’s life. Since your engine needs to run to power its alternator — the device that charges the battery — you should use or at least start and run the car regularly. Be sure to take it out for longer drives occasionally, as short trips don’t give your battery a chance to recharge. While the car should be able to power all its electrical systems at idle, about 30 minutes to an hour of highway driving should restore a good charge to a low battery.

To ensure that your battery is always topped off, consider a trickle charger for when the car is stored in cold temperatures or not in regular use. To preserve battery charge when you’re away from home, avoid using the air conditioning or infotainment system while the engine is not running, as these accessories drain a battery quickly. Finally, regularly check and clean the battery terminals so that they don’t become corroded and unable to transmit power properly.

No one likes a dead battery on a cold winter morning. Understanding how cold weather kills a car battery and following proper battery maintenance practices can help your battery last longer and reduce your chances of discovering a dead battery when you have places to be.

Check out all the car battery products available on NAPA Online, or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information about car batteries, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of FreeImages.

Nicole Wakelin View All

Nicole Wakelin covers the automotive industry as a freelance journalist for a variety of outlets. Her work includes news pieces, podcasts, radio, written reviews, and video reviews. She can be found in The Boston Globe, CarGurus, BestRide, US News and World Report, and AAA along with lifestyle blogs like Be Car Chic, The Other PTA, and She Buys Cars. She is active on social media with a large following on both Twitter and Instagram and currently serves as Vice President of the New England Motor Press Association.

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