Winter can be harsh on your car battery, battery fluid can freeze, the engine will be hard to start, and your car might drain faster in cold. Even an expensive fully charged battery won’t be able to perform its best in cold temperatures. But that raises the question, does a battery drain faster in cold?

Your car battery doesn’t actually drain faster in cold, it’s just that cold causes the battery to have less voltage and capacity than normal, making it seem like it’s draining faster. Although your car can consume up to 2x more power to start in cold, which can definitely “drain” the battery.

This might come as a surprise, but “drain” is not an appropriate word to describe what you’re experiencing with your car. At startup, yes, your battery will drain because the most taxing use of a battery is while cranking, which cold weather can increase by 2x. But apart from that, your battery isn’t draining, what is actually happening is. Since the colder the battery, the lower the voltage/capacity, while increasing the required power to start the engine. It will seem like your car is drawing more power (which can definitely still be the case, as you will likely have more electronics on in winter, like a heater, charger, headlights, etc.) when in reality, your battery just doesn’t have the same capacity and voltage in cold as it has in on a warm day. According to aaa.com, At 32°F, the car’s battery loses about 35% of its strength. And at 0°F, it loses up to 60% of its strength while your engine requires nearly twice as much power to start.

Why Do Batteries Drain Faster In Cold?

In Short: Batteries “drain” faster in cold because:

  • Reduced capacity and effectiveness due to slower chemical reactions
  • Engine oil gets thicker, which can make the engine be more difficult to start
  • More electronics are used in winter, straining the battery.
Voltage/Ah loss in cold Graph

Slower Chemical reactions

Cold temperatures make molecules move slower and collide less, this is true for virtually everything, including the battery. When the battery is cold, it won’t be able to supply enough current to keep up with the demand. To make matters worse, your capacity will be decreased too, this will be felt especially hard if your battery was already old and was starting to lose its capacity due to age. As the battery drains, its voltage goes down quicker than a warm battery and continues decreasing with lower temperatures, this gives you the feel of “draining”, when in reality, energy doesn’t go anywhere, it’s just that your car cannot use voltage lower beyond a certain point, which cold weather accelerates. The graph above can help you understand. 

Engine Oil Gets Thicker

Engine oil gets thicker when cold, especially if you’re dealing with straight-weight oil that doesn’t have different viscosity ratings for cold and hot weather. This can make the engine more difficult to start, which can cause the starter motor to draw more amperage, eating up the battery capacity even more at startup.

Electronics

The thing that actually “drains” your battery is probably the electronics you are using in winter. Because with cold weather and early sunsets comes the need to use a heater, headlights, etc, more often. Unless you have some high-performance alternator, your charging system can struggle to keep up. This can be felt even harder if your car battery was already suffering from old age.

One thing to keep in mind is that, when a battery is not in use, it will slowly lose its charge as a result of leakage between the terminals, which is another reason your battery can be draining. You may be surprised, but cold weather can actually help preserve battery charge since chemical reactions are slower. So a battery that is refrigerated can last twice as long as the one at room temperature.

How To Prevent Your Battery From Draining In Cold

In Short, to keep your battery from draining in cold you need to make sure:

  • The battery is healthy and without corrosion.
  • Keep your battery fully charged to prevent the battery from freezing.
  • Put your battery in a thermal blanket (battery warmer)
  • Use a block heater which should come with most modern cars.
  • Alternatively, you can park your car in a garage, away from wind and snow.

Assess Your Battery 

Keeping your battery healthy is very important, especially in winter, Make sure that:

  • It isn’t old
  • Is functioning properly
  • Does not have corrosion
  • Does not have dirt

Batteries aren’t made equally. Some last anywhere from 3-5 years, while some can reach up to 10. It is important to check it before we continue as having an old or ineffective battery can severely hurt your performance in winter. 

If it is time for a new battery, make sure it is the same size, voltage, and terminal location/orientation. If you’re unsure, check your owner’s manual or do a quick google search.

Related: How To Tell If a Car Battery Is Bad

Showing battery corrosion

Corrosion and dirt also play a big role in battery health, as corrosion and dirt can hurt your performance just as much as an old battery. Low temperatures increase electrical resistance and thicken engine oil, when you have corrosion/dirt it can add up to the resistance, making your battery work even harder. If you notice white powder or something that looks like dead skin or dirt, clean it. Fortunately, you don’t need a special cleaning spray or fancy tools (although you can definitely still use them). All you need is a moist rag, some baking soda, water, and a toothbrush:

  • Cover the battery terminals with soda
  • Pour some water on each terminal.
  • It should react and start bubbling
  • Use a toothbrush or a bristled brush to scrub the corroded area.
  • Clean the remaining with a rag
  • If you need to, you can repeat the same processes for battery cable ends.

Make sure to regularly check the battery to keep your battery running smoothly in winter

Keep your battery charged

If your battery is fine, one of the best things you can do is keep your battery charged. According to Interstate Batteries, a fully charged battery will not freeze until -76F, while a fully discharged battery could start to freeze at around 32F.  This doesn’t necessarily prevent your battery from draining in cold, but this makes sure it doesn’t die sooner than you think. Although as explained, a cold battery will definitely die faster than a warm one.

Put Your Battery In a Thermal Blanket

A battery blanket (also known as a battery warmer) is an insulated wrap for a vehicle’s battery. Some are electrically heated, while some are not. If heated, it is the BEST and most efficient way to keep a battery from draining in cold weather. A battery blanket can prevent:

  • Battery fluid from freezing
  • Slow chemical reactions
  • Slow charging times

Battery blankets are cheap and very easy to install while making your life in winter much easier. It is a great addition for anyone living in or experiencing cold climates.

Related: Can You Put a Different Size Battery In Your Car?

Use a Block Heater

Showing what a block heater is

A block heater will keep your engine oil warm when cold, making your vehicle easier to start and draw less power when starting, preventing your battery from draining when cranking. Most cars nowadays have a block heater included in the standard specification or as an “extra option” of your vehicle.

Park Your Car In a Garage

If you don’t want to get a battery blanket or a block heater, you could always park your car in a garage to avoid wind and snow. Although if your garage isn’t heated, there’s nothing it could do about the cold. But it should be slightly warmer in your garage than outside. Now if you combine a battery warmer, block heater, and a garage. You will have an ultimate setup to survive cold weather and prevent your battery from draining in cold. 

Unplug Electronics

This might seem like a stupid idea, but it can actually work. If your battery isn’t fully charged and is suffering from cold weather, it may be a good idea to turn off/unplug the electronics you have. When your battery isn’t fully charged and has decreased capacity/voltage due to cold, your car might struggle to start even more as your car cannot use voltage/capacity lower beyond a certain point, which electronics could accelerate.

Drive For 10+ Minutes

Once you have done everything/some of what we listed above you will be able to more easily start your car and prevent drain in winter, after which it is important to drive 10 minutes or longer to keep your battery going. Each time you start your car it uses about 5 to 10% of the capacity, which won’t be recharged back after a short trip, which can cause premature failure of the alternator.