Yes, frigid weather may reduce your EV battery range. Here's how to prepare

Recent news reports out of the U.S. have recounted the problems Tesla owners have faced during the extreme cold weather across North America, including loss of battery power, extended recharging times and long lines at charging stations.

Yes, freezing temperatures can have a significant impact on an electric vehicle's battery, but experts say there are ways to mitigate the effects of extreme cold.

Why does the cold weather impact EV battery power?

The technical explanation for the loss of power has to do with the lithium ions that produce electricity in an EV battery. When it gets cold, they flow more slowly through the liquid electrolyte and release less energy.

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Seattle-based Recurrent, a company that tests and analyzes electric vehicles, explains on its website that EV engines are more efficient than internal combustion engines (ICE) because the former don't generate "waste heat."

However, the waste heat in ICE cars can be used to warm the vehicle's interior in cold temperatures. 

EVs need to produce that energy themselves, meaning "the heaters that keep the car warm generally draw energy from the high-voltage battery, reducing how much capacity is left for driving," the Recurrent website said.

How much does cold weather affect an EV's battery power?

Some EVs can lose up to 30 per cent of their range in freezing temperatures, according to Recurrent. 

In its latest report, based on data from 18,000 vehicles, Recurrent found that 18 popular EV models maintained an average of 70.3 per cent of their range in freezing conditions. But that performance varied depending on the model. For example, the report found that the range of the Audi E-tron fleet dropped about 20 per cent, compared with the Chevy Bolt (32 per cent) and Tesla Model S (55 per cent).

Consumer Reports conducted its own tests and found the cold weather can have a significant impact even before the temperature drops to freezing. Their tests found that the range starts to drop at 4 C. Cold weather, it found, can drain about 25 per cent of range when driving at higher speeds of just over 110 km/h.

"There's validity to the concern that you are going to lose some range in the really cold weather," said Cara Clairman, president and CEO of Plug'n Drive, a Canadian non-profit organization that seeks to answer consumer questions about electric vehicles.

She said range loss is less of a concern in more recent models compared to older models.

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But Clairman pointed out that while vehicles may lose some range, most drivers on a typical day aren't driving anywhere near the top of their vehicle's range, which for most is between 400 and 500 kilometres on a full charge.

"Let's say you might lose 20 per cent. That's only an issue for you if that particular day you're driving 350 kilometres," she said. "So just keep in mind it's probably not an issue for most people."

How much longer do cars have to be charged in cold weather?

The vehicle controls the charging rate, not the charger, meaning when temperatures are low, the EV's software reduces its charging power to help avoid stressing the battery, according to the website of Electrify America, a U.S.-based organization promoting zero-emission vehicle adoption.

EVs can take longer to charge when it's cold partly because most are designed to boost their battery temperatures when the thermometer drops, Alex Knizek, manager of automotive testing and insights at Consumer Reports, told CBS MoneyWatch.

"This power to do so comes from the battery itself, reducing range," Knizek said. "This also has an impact on charging speeds. If the battery is too cold, it will charge slower and may need to heat itself up before the charging speed can increase."

This can result in a doubling of charging time, or even a tripling in some older EVs.

How can EV owners offset the impact of cold weather on their battery?

Albert Gore III, executive director of the Washington, D.C.-based Zero Emission Transportation Association, said EV owners should consider "preconditioning" their vehicles before use.

"A great feature of nearly every EV on the market now is that it's very easy to use your phone to turn on the heat five minutes before you get in the car," he said. "That doesn't just make the car more comfortable, it also helps to precondition the battery, and that will extend your range, depending on what type of vehicle you have."

While preconditioning is available with most EVs using your phone's app or by setting up a departure time, some vehicles also offer a "winter weather" feature that is specially designed to keep battery temperatures in an ideal zone so they are always ready when you start to drive, according to Recurrent.

Gore's organization recommends plugging the vehicle in and running the heating system for 20 to 30 minutes before taking it for a drive.

As well, he said drivers should plan to charge more frequently during colder weather, staying between 20 per cent to 80 per cent of charging range.

"Also, try to ensure that if you're going to leave your car parked for a while, that you're leaving it with more than 20 per cent range on the battery," Gore said.

Recurrent suggests that once the vehicle is on the road, drivers should turn down the cabin heater and use seat warmers and a heated steering wheel to stay warm. These features use less energy and provide targeted heat, giving you more battery capacity to travel. 

As well, if possible, owners should store their EV plugged in with a maximum charge setting of 70 or 80 per cent, Recurrent said. That way, the car can pull energy from the wall to keep warm, rather than using the battery. Otherwise, you may return to a lower battery capacity than expected.

Recurrent said EV owners could also consider equipping their vehicle with a heat pump, which is newer technology that can help preserve range when it's cold. This feature is standard in some EV models and optional in others.

On-board heat pumps draw warmth from outside (even when it's cold) and run it through a condenser that raises the temperature, allowing for warm air to be pumped into the cabin, Recurrent says on its website.

Anna Stefanopoulou, a professor of mechanical engineering at the University of Michigan, said heat pumps use electricity in a much more efficient way.

"It's like an air-conditioning system, you would turn it on when you need it," she said.