How to Prevent a Dead Battery in Cold Weather
Our best battery expert weighs in on how you can prevent a dead battery this winter.
Car batteries don’t like the cold.
The colder the weather gets, the weaker they are. Even a strong, fully charged battery won’t feel 100% if the temperatures drop enough. And if your battery is only half-charged, it’ll freeze solid at just -10 F. If you live in Canada, the Dakotas, Minnesota or Wisconsin, you’ve probably seen a few frozen batteries. Cold snaps and wintery mixes threaten every battery.
And you rely on your battery in the winter.
Holiday dinners, parties, visiting grandmothers who live over rivers and through woods — you’ve got places to be, family to hug and eggnog to sip. Here’s the problem: You may only discover a dead battery the very moment when you want to get going.
Interstate Batteries Lab Manager Jeff Barron took a few moments out of our Innovation Lab in Dallas to give some expert advice to help you prevent cold from killing your car battery. In fact, he and his team freeze batteries professionally. They put all kinds of batteries through rigorous tests from the Society of Automotive Engineers and the Battery Council International, ever pressing for consistent quality in every Interstate product. In the ISO/IEC-accredited laboratory (that’s 17025: 2017 accreditation for those in the know,) they also run batteries through years of cycles in a matter of weeks and occasionally pick them apart — all to understand how to make the best even better.
Jeff gave a tour of their walk-in freezer as he explained what happens to dead batteries and what anyone can do to prevent problems.
Let’s talk about what you can do to avoid a dead battery this winter.
This walk-in freezer takes batteries down to 0 degrees Fahrenheit. Surviving the cold is a true test of any car battery. | Photo: Youssef Sleiman
- Get your battery checked.
- Keep driving for 10 minutes or longer.
- Park your car in a garage, if possible.
It’s simple and easy — and usually free at repair shops across North America.
“If it’s gonna get cold, you want to get it checked,” Jeff said. “Drive it to a shop and get it checked, just like you want to check your anti-freeze.”
Drive to your closest Interstate Batteries-authorized dealer and ask for a battery test. They’ll pull out either the classic ED-18® or Interstate’s newest tester, the IB Pulse® to look for any weakness in your car battery — and even tell you the temperature that’ll kill the battery.
"That’s why we’ve got all these customers that go to our Firestones and NTBs, and they’re real religious about getting their car in to do regular maintenance,” he said. “They go in and do the battery check on it — for free.”
Then you can pick where and when to deal with your car battery, instead of a dead one demanding you deal with it right then.
Ask for a free battery check at any of these 150,000 locations
Where can you get a free battery check near you? Put in your city or ZIP code, and we’ll show you dozens of locations nearby. Or just look for our logo in any of the auto shops near you.
Next on the list for preventing winter battery problems: Driving.
Driving every day keeps the cold at bay. Your engine warms the battery when you drive. Even a healthy battery can stay strong so long as you’re taking the drive.
“As long as you’re doing daily drives that are not short drives, and I say short, like a mile or two and you stop,” he said. “Ten minutes, 20 minutes — as long as it’s getting ‘exercise,’ as we would call it, you’re keeping the acid moving, you’re keeping some kind of charge going into it.”
Here’s a rule of thumb: Drive the length of your commute, even if you’re on a holiday break.
The average commutes for Americans and Canadians are longer than 20 minutes one way, according to census data from the U.S. Bureau of Statistics and Statistics Canada. Making a similar drive — even if it’s to a café, the in-laws or a grocery store on the far end of town — can keep your battery exercising and ready.
However, the moment your start-up seems to slow down, get to a repair shop. That’s an early sign your battery is going to die. And driving won’t help bring a dead battery back to life.
Driving will keep winter damage at bay.
“A hutch is all right. People always think about wind chills. Well, that doesn’t always affect the battery, even if it’s in direct wind,” he said. “Typically, it’s the temperature that freezes the battery.”
Ambient temperatures can kill your battery if they drop too low. Instead, park in these places:
- In your garage
- In parking garages with a lot of come-and-go traffic
- Near heated equipment
- Close to warm buildings
- In spaces with lots of direct sunlight, which will warm the body of the car
- Anywhere that can be warmer than shaded, bare outdoor weather
How warm does it need to be? It depends on how weak your battery already is.
The weaker your battery, the warmer it has to be to make sure you can start your car. It depends on your battery’s size, power and age. To get an exact picture, take your car to get the battery checked.
Now, the battery’s polypropylene plastic case offers thermal protection, too. Its internal design and material structure keep the water-acid mixture (electrolyte) about five degrees warmer. But the more discharged the battery, Jeff explained, the thinner the mixture is. At 10% charge, the liquid inside is mostly water — but even then, water in the polypropylene case won’t freeze solid until temperatures drop to 28 F, instead of 32 F.
A fully charged battery can resist incredibly cold temperatures. (The thermometer has to read -80 F to freeze a fully charged battery.) But that strength disappears if your battery wears down enough. If your battery is only half-charged, it could turn to a block of ice at -10 F overnight. By the way, your battery-popsicle would have failed your car long before the temperature fell that low.
Test your battery before winter does
Winter kills car batteries — unless you and your mechanic catch battery weaknesses first.
Visit any of these locations to test your car battery.
Battery warmers, insulators, electric battery blankets, thermal wrap — they go by many names, but they’re all a corrosion-resistant heat blanket for your battery. They’re available online or in stores.
“It’s a safety blanket for your battery,” he said.
In a pinch, you can throw a dry, thick bath towel on the battery after you’ve driven enough to warm the engine. As soon as you park, pack the towel onto the battery — and the extra coating will retain the engine heat. Just be sure to remove the towel before you start the engine again.
In fact, most car makers already give your battery extra coating.
The problem is most amateur mechanics replacing their own car battery will usually trash the protective battery coating.
The expert advice: Don’t trash your battery protection.
“If there’s a fiber-wrap mesh or even a plastic cover on it, those need to go back on there. They’re there for a reason from the manufacturer,” Jeff said. “Even though that plastic is really thin, and it seems like it’s just nothing but a hindrance to you, it’s actually a protector because of the heat it gets surrounding.”
“The key thing is making sure you keep it charged,” Jeff said. “That’s the most important thing.”
When the temperature drops near freezing, a battery maintainer or trickle charger may not keep your battery alive. But it’s not the charger’s fault.
It’s that the weather is too cold.
“Batteries just aren’t as efficient in cold temperatures, whether they’re accepting a charge or cranking an engine,” Jeff said. “That’s when CCA or cold cranking amps really come into play. Those ratings say how much power they should give when it’s below freezing.”
Recharging your battery is a good idea at any time of the year to extend its life. However, that’s not easy when it’s 32 F. At that temperature, a typical battery is only 65% efficient, both at recharging and giving power. You need more voltage or more hours to recharge the same battery.
And you do need to recharge your battery. It’s a sensitive, sophisticated, electrochemical device. Its life depends on getting juiced up every now and again.
However, the colder it is, the harder it gets to recharge your battery.
In fact, your alternator may not be able to give your battery all the power it needs to spring back to life, unless you’re traveling a long distance.
How do you recharge your battery then?
Your best move is to visit a repair shop. If a battery test reports a significant weakness, your local shop will have the equipment to recharge your battery’s life.
Or if you’re scientifically and mechanically inclined and have a standard sealed lead-acid battery, you can get out a hydrometer and check the specific gravity to see if your battery needs recharging. You should not try to open an AGM battery because you shouldn’t have to.
In short, remove your car battery, open the vent caps and add deionized, distilled water. Then, test the specific gravity of the battery’s acid-water mixture to see that it’s fully charged, using the following table.
Battery State of Charge by Specific Gravity
Charge Specific Gravity
When the electrolyte mixture inside the battery is full and room temperature, you’ll be able to charge it easily and get more years of life out of your car battery.
If you have a frozen battery, here's what you should not do.
Basically, to avoid having a dead battery, get prepared before you have the cold come in. But what if it’s already too late?
What if the worst happens? Batteries aren’t as easy to freeze as ice cubes in a tray, but it’s still possible. What happens then? And what should you do about it?
First of all, remember that water expands as it freezes.
“So, what happens when you look inside when these things start freezing, the plates are going to start getting all deformed — and their plates start touching,” Jeff said.
There’s only so much space inside the plastic battery case. As water expands into ice, it’ll warp the lead plates and crack open the case. Even when the battery and its inner liquids thaw out, the battery has probably already formed into a short circuit. After all, it’s frozen solid, and the negative and positive plates have joined.
“Well, now you have a direct short in there,” Jeff said. “Then there’s a high probability you’re going to have what we call, ‘rapidly disassembling batteries.’ Especially if you’re trying to jump-start it.”
That means exactly what you think it does.
In that instance, don’t do anything with your battery if you suspect it’s frozen.
See the frost and cracked case on this golf car battery? The only thing this battery should start is a conversation. | Photo Jeff Barron
Don’t try to crank or jump-start your battery if your battery shows
- Frost on the terminals or plastic case
This warning is serious.
So serious that we wanted you to have an easy, catchy way to remember what to do if you have a frozen battery.
You know the popular winter song. Just sing it to these words.
What You Should Do With a Frozen Battery
A Frozen Parody
Let it go, let it go
Don’t jump or crank it anymore.
Let it go , let it go
Drop the hood and slam the door.
Ar-en’t meant to freeze.
Let’s call help, oka-ay?!
There’s a chance of rapid disassemblage anyway.
Let's make sure your battery is winter-ready
Fully charged batteries resist the cold better than weak, half-spent batteries. So, before your winter drive, take your car to any of these locations to get a battery test.
There’s nothing magical about predicting battery failure. Just ask one of these reliable technicians for a free battery test.