by Alaska’s rugged and frozen interior, where it can get as cold as minus 50 Fahrenheit (minus 46 Celsius), is not the place you’d expect to find an electric school bus.
But here’s bus No. 50, with a cartoon horse decal on its side, quietly traversing some 40 miles of snowy and icy roads every day in Tok, ferrying students to school not far from the Canadian border.
It works normally on the daily route. But cold temperatures rob electric vehicle battery life, so the No. 50 can’t go on longer trips or to Anchorage or Fairbanks.
It’s a problem some electric passenger vehicle owners and public transit workers are finding in cold climates around the world. At 20 degrees F (minus 7 degrees Celsius), electric vehicles just don’t go as far as the ideal 70 degrees. Part of it is that keeping occupants warm with traditional technology drains the battery.
So longer trips can be difficult in colder weather. Transit authorities like Chicago, which has committed to converting its entire bus fleet to electricity by 2040, must take emergency measures to keep electric buses charged and on schedule.
Some carmakers and drivers fear that lower battery range in the cold could limit the acceptance of electric cars, trucks and buses at a time when transport emissions must be cut sharply to tackle climate change. There is hope. Scientists are racing to perfect new battery chemistries that don’t lose as much energy in cold weather as current lithium-ion systems.
Also, cars equipped with efficient heat pumps do not lose as much range in the cold.
“It’s a problem to have batteries in cold weather and we have a pretty cold climate, one of the coldest in North America,” said Stretch Blackard, owner of Tok Transportation, which contracts with local schools.
When the temperature hits freezing, his cost to operate Tok’s electric bus doubles. Tok has some of the highest electricity prices in the country.
In the coldest weather, from 0 to minus 10 F (minus 18-23 C), the electric bus costs about $1.15 per mile, compared to 40 cents per mile for a diesel bus, Blackard said. The cost of the electric bus drops to 90 cents a mile when it’s hot, but he says the cost makes it unviable and he wouldn’t buy another one.
Many owners of personal electric vehicles also find that long distance travel in the winter can be difficult. Electric vehicles can lose anywhere from 10% to 36% of their range as cold weather hits at least a few times each winter in many US states.
Mark Gendregske of Alger, Michigan, said it starts to get serious when temperatures drop into the 10-20 F (minus 7 to minus 12 C) range. “I typically see more than a 20% degradation in range as well as charging time,” he said while recharging his Kia EV6 in a shopping mall parking lot near Ypsilanti, Michigan. “I go from about 250 miles of range to about 200.”
Gendregske, an engineer for an auto parts maker, knew the range would be reduced, so he said, with programming, the Kia EV still gets him where he needs to go, even on a long drive.
Some owners, however, did not expect such a large drop in winter. Rushit Bhimani, who lives in a northern suburb of Detroit, said he sees about a 30 percent lower range in his Tesla Model Y when the weather gets cold, from 330 miles per charge to as low as 230. “They should clarify that,” he said. while loading up just south of Ann Arbor on a trip to Chicago.
About three-quarters of this EV range loss is due to keeping occupants warm, but speed and even highway driving are factors. Some drivers go to great lengths not to use much heat so they can travel longer, wearing gloves or sitting in heated seats to save energy.
And sure, gasoline engines can also lose about 15% of their range in the cold.
The loss of range has not slowed EV adoption in Norway, where nearly 80% of new vehicle sales were electric last year.
Recent tests by the Norwegian Automobile Federation found that the models really differ. The relatively affordable Maxus Euniq6 came as close to its advertised range as possible and emerged as a winner. It finished just 10% short of the advertised range of 354 km (220 mi). The Tesla S was about 16% percent below its advertised range. At the bottom: Toyota’s BZ4X, which topped out at just 323 kilometers (200 miles), nearly 36% short of its advertised range.
Nils Soedal, from the Federation of Motor Vehicles, calls the issue “no problem” as long as drivers take it into account when planning a journey. “The big issue is really having enough charging stations along the road” and better information about whether they’re working properly, he said.
Temperatures ranged from just below freezing to minus 2.2 F (0 to minus 19 C) during the test, over mountains and along snowy roads. The cars were driven until they ran out of juice and stopped.
Recurrent, a US company that measures battery life in used electric vehicles, said it conducted studies monitoring 7,000 vehicles remotely and came up with findings similar to the Norwegian test.
CEO Scott Case said many EVs use resistance heating for the interior. The ones that do best are using heat pumps.
Heat pumps draw heat from outside air even at low temperatures, and have been around for decades, but have only recently been developed for cars, Case said. “That’s definitely what should be in all these cars,” he said.
Inside batteries, lithium ions flow through a liquid electrolyte, producing electricity. But they travel more slowly through the electrolyte when it cools and don’t release as much energy. The same thing happens the other way around, slowing down charging.
Neil Dasgupta, associate professor of mechanical engineering and materials science engineering at the University of Michigan, likens it to spreading cold butter on toast. “It just becomes more resistant to cold temperatures,” Dasgupta said.
General Motors is among those working on solutions. With the tests, engineers can make changes to battery and heat management in existing cars and learn about future models, said Lawrence Ziehr, project manager for energy recovery in GM’s electric vehicles.
Last week, GM sent a squadron of electric vehicles from the Detroit area to Michigan’s frigid Upper Peninsula to test the effect of cold weather on battery range.
Despite stopping to charge twice along the way, a GMC Hummer pickup, with about 329 miles of range per charge, made the 315-mile trip to Sault Ste. Marie with only about 35 miles to go, barely making it to GM’s testing facility. After finding a defunct charging station at a grocery store, the engineers went to a nearby hotel to get enough juice to complete the trip.
And in universities, scientists are working on changes in chemistry that could make the loss of cold weather a thing of the past.
The University of Michigan’s Dasgupta says they are developing new battery designs that allow ions to flow faster or enable fast charging in the cold. There are also chemical batteries such as solid state that do not use liquid electrolytes.
He expects the improvements to make their way from labs to vehicles in the next two to five years.
“There really is a global race to increase the efficiency of these batteries,” he said.
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David Keyton contributed from Stockholm, Sweden. Krisher reported from Chicago and Sault Ste. Marie, Michigan.
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