Why does cold weather affect the range of an electric vehicle (EV) battery?

You may have noticed that your battery range drops during cold weather. Why does this happen? Was it the 5 pounds you gained over the holidays? Is your significant other hiding a large gift for you in the trunk? No and not likely. Recurrent, a website that reports on the health of EV batteries, notes that cold weather slows the chemical and physical reactions that make batteries work, specifically conductivity and diffusivity, leading to:

• Longer charging time
• Temporary reduction in range (the capacity, the amount of charge able to be stored by the battery, is lower), primarily due to the heating system. Since the energy for heating and cooling your car comes from the same battery that propels the car, use of climate control can pull charge away from the primary battery.

Internal combustion vehicle (ICV) engines are inefficient. Because of this the heat that is generated from the lost energy can be used to heat the cabin. EV engines generate less heat and this heat is used to warm the battery. To heat the cabin, energy needs to be sourced from the battery which will then reduce the range.

The Norwegian Automobile Foundation (NAF) conducted a test on the range of popular EV models driven during winter conditions and found that EVs lose on average about 20% of their range in colder weather and also charge more slowly. For individual models see their test results here. Recurrent also has their range report here.

In 2019, the American Automobile Association (AAA) reported that, on average, an ambient temperature of 20°F resulted in a 12% decrease of combined (city plus highway) driving range (when compared to testing conducted at 75°F). If the heater is then used to heat the inside of the vehicle, the average driving range is decreased by 41%.

What are strategies to help improve the EV battery range in cold weather?

Most EVs have a monitoring system that will keep the battery in a certain temperature range to help extend its lifetime. In addition, check to see if your car has a preconditioning feature which allows you to heat up the battery and cabin from an app on your phone. You can then turn this on while your car is still connected to a charger, which will help save battery power. If you do not have this feature, then try to remember to take the time to heat up your car while you are still plugged in. Also park your car inside a garage if possible.

• Utilize the seat/steering wheel warmers instead of the heater as these will use less power.
• Before charging your car in cold weather, warm up your car by driving around, especially if the outside temperature is below freezing. This will put less strain on the battery.

What happens when the EV battery fully loses all of its power?

Fortunately, you will not come to an automatic stop. In their test, NAF found that all EVs give plenty of warning before they run out of power, and you maintain driving comfort and speed even after the first warning. Their test also showed that most EVs maintain speed until the last few kilometers. Then the drivers all experienced a loss of acceleration and a limit on maximum speed. In some cars the heating automatically shut down.

What happens to an EV battery in hot weather?

Recurrent states that temperature affects the rate and efficiency of chemical reactions inside a battery. Higher temperature means there is more total energy in a system, so it leads to faster reactions across the board. This means that all reactions happen faster in high heat – both the ones that produce energy, and the  “unwanted” chemical reactions that make batteries degrade. AAA notes that, on average, an ambient temperature of 95°F resulted in a 4% decrease of combined driving range (when compared to testing conducted at 75°F). When using air conditioning, on average, an ambient temperature of 95°F resulted in a 17 percent decrease of combined driving range (when compared to testing conducted at 75°F).

What are strategies for improving the EV range in hot weather?

It is all about trying to keep the battery cool.  Try to cool the battery and cabin while plugged into a charger. Use the preconditioning feature if your EV has one.

The AC uses less battery power than the heater does — but drivers should focus on using it efficiently.

Ok, don’t stress…

You may be thinking oh great, more things to think about with EV ownership but you are likely already doing at least some of these things and the other recommendations are easy to employ. Don’t forget that EVs require minimal maintenance compared to ICVs which means no extra time spent on getting oil changes and other routine maintenance done. Now go check the trunk to see if maybe there really is a gift for you!

Do you have a question about sustainability or climate change? Let us know. Write to Darren at askdarren@acterra.org and maybe your question will be featured in our next “Ask Darren” feature!

Editor’s note: On October 25, this piece was corrected to remove an outdated link.