Why Do Car Batteries Die in Winter?

Few things are more frustrating than climbing into a cold, snow-covered car or truck only to hear the dreaded “click-click” of a dead battery. It happens to the best of us. But why does a car battery’s life seem to end more frequently in winter? Read on for the reason why.

Car battery

Source | Flickr

The inner life of your vehicle’s battery

First, a quick refresher on the science happening inside a car battery. Lead acid batteries are the most common car batteries because they’re inexpensive and fairly dependable. They’re made of a plastic case that houses a series of lead plates immersed in a pool of electrolyte—a mix of water and sulfuric acid. Each pair of plates makes up one “cell.” When fully charged, each cell in a lead acid battery produces 2.1 volts. So, a 12-volt battery consists of six cells.

The lead acid battery doesn’t produce a charge, but receives and stores an initial charge through a chemical reaction between the cell’s lead plates and the electrolyte. But as the chemical reaction occurs, the positive and negative lead plates are slowly coated with lead sulfate. This process is known as sulfation, and it reduces your battery’s ability to hold a full charge.

To complicate matters, lead acid batteries experience self-discharge, a natural loss of charge over time. Left too long without a fresh charge, a battery can discharge beyond recovery.

So why do batteries fail in winter?

Extreme heat or cold can increase your battery’s rate of discharge, making winter a triple-threat to your battery. All that exposure to summer’s heat evaporates the water in the electrolyte, increasing sulfation. Then winter rolls around, and freezing temperatures slow the chemical reactions occurring inside a lead acid battery, further reducing your battery’s ability to perform.

At the same time, a cold engine and sluggish oil demand more power, while power-hungry features like heat and defrost place more demand on your battery. Although lead acid batteries last an average of four years, they can fail earlier under the right (or wrong) conditions.

Signs of a failing battery

Your battery won’t always warn you before it fails, but here are common signs to watch for:

    • Headlights dim yellow instead of white
    • Dashboard battery warning light is on
    • Electronic accessories fail
    • Engine cranks more slowly
    • Dome lights dim
    • Car horn sounds unusual
    • Battery case swollen or cracked
    • Smell of sulfur or rotten eggs
    • Battery is more than three years old

The best way to find out if it’s time to replace your car battery is to have your battery tested.

Have you had to deal with a dead battery in winter? Share your experience in the comments.


  1. John Shade says:

    The battery warning light does not tell the condition of the battery but that it is not receiving a charge from the
    alternator. The only way to tell of the condition of the battery is to have it tested.

  2. Another good article, however I wouldn’t consider a lead acid battery inexpensive with an average cost these days of about $150. with that cost even higher for many European vehicles.

  3. One of the best practices for extending battery life is to use a battery maintainer. Any equipment, such as your lawn mower, atv and motorcycle, that do not get used every day, will benefit from this.

    • Bob Weltzien says:

      Yes, a trickle charge or the lowest setting on the charger. Too much charge will warp or sulphate the lead plates.

  4. Bob Weltzien says:

    Running your car with a chronically undercharged battery will also shorten alternator life. The alternator is designed to supply power for a car while it is running, not to charge the battery. Periodically applying a trickle charge to your battery will extend it’s life.

  5. Bob Weltzien says:

    Also remember to periodically clean the top of the battery and the terminals. Current can leak across the acid on top of a battery.

  6. Tom Goodhart says:

    A long time ago I had a one year old Chevy Cavalier that would not start one cold morning, despite being on a trickle charger since the night before. The AC Delco batteries at that time had a “eye” indicator that showed whether the battery was okay or not. I jump started the car from another and went to work which was just a couple of blocks from a Chevy dealership. I pulled into the service dept. and shut it off, did the paper work and then got a ride to the office. Later, when I went to pick it up, the service writer told me “they could’t get it started, and had to jump it to get it out of the incoming service area to actually move it to a work bay. Turned out to be a dead cell (not the one with the “eye”. So I was only getting 10+ volts of power. They replaced the battery under warranty and I had no further problems. The service writer confirmed what I thought that the only thing that that “eye” was good for was to tell you the condition of that one cell. I don’t know if AC Delco still puts the “eye” indictor in their batteries but it isn’t really any good to know the condition of the “whole” battery.

  7. That is exactly why I spent a little money to buy and keep a good portable jump starter in my trunk. I know I’ve used it a few times- on other people’s cars. It’s much easier to use than jumper cables, and I can just plug it in at home when I’ve used it. So far, it’s worked pretty well. For those other people, I’m their saving grace!

  8. Good article! Why are using lead acid batteries when AGM batteries perform much better and last longer?

    Worth considering if you need a battery replacement.

  9. The battery article was good and even Advance stated batteries are only good for 4 years. Well I and others I know are done with the Gold batteries at Advance. as you will see later in this comment. They are 7 year batteries but only last about 42 months on the average. Then you are out of the 3-year free replacement so you are pro-rated back to the beginning and the cost is almost the same as buying a new battery. Those Gold batteries at around $120 to $140 depending on the application are way overpriced unless you really did get 6 or 7 years out of them. I have 8 cars they are all garaged and it is heated in the winter. I now purchase 42month Delco batteries for much less than the Advance Gold battery and just change them every 4 years and save money. then I don’t get the false feeling that my Advance battery is going to last 6 or 7 years like Advance advertises. We have a group (15 to 20) of car guys that meet once a week for lunch. When I brought this Advance battery life up almost all them agreed and stated they quit using Advance batteries for the same reason. By the way about half of this car guy group is made up of retired engineers (some electrical engineers) for a large corporation. While most of them agreed the Power Frame that is used should produce better battery life they all agreed this must just be used as a sales promo as they do not last any longer than other batteries. All the guys in this group have between 4 and 10 vehicles so these guys need a lot of batteries. Another point is some of these cars are not driven during winter months, but we all use Battery Tenders on our cars during this down time and most of these cars are in heated garages or buildings. Conclusion we came to was purchase a 42 to 48 month battery and just change it every 4 years.

  10. A few things to remember in the winter months… not only is your oil at it’s thickest first thing on a cold morning but due to daylight savings time you’re using headlights going to and from work along with heaters and defroster. Usually this puts a heavy load on already stressed batteries. We had a problem which we thought was due to the battery but it boiled down to excessive load and not enough charge time. We load tested two batteries and they were fine. We changed oil and set a policy that for the last few miles home, shut down the defroster, seat warmers and lower the fan speed. Problem solved. The next morning everything fired right up. Things to consider…many new cars have batteries that just make it. In other words they’re barely enough to do the job. Furthermore as mentioned, the cold and constant draw during winter can easily suck the juice and without enough charge time you may be left with a non starting car the next morning. A tricl4 charger may help but by shutting off a few things may bump up what’s needed. All new cars draw power even when off…alarm systems, radio to unlock doors, etc.

    • Just to note that daylight savings time is active in the summer months. The winter months are normal (or actual, or whatever time you want to call it), so daylight savings time is not causing the lack of light in the winter, but rather helping us in the summer.

  11. randy koenig says:

    the heater and defrost use hot water not battery power. The blower is electric but is really used year around today with AC

  12. Keep your terminals clean-and as bad as the Advance (& every other Johnson Controls built) battery leaks acid around the posts, be sure to put the grease impregnated washers under the clamps, a nice shot of grease or battery protectant on top doesn’t hurt either

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