TOK, Alaska – Alaska’s rugged and freezing interior, where it can get down to minus 50 Fahrenheit (minus 46 Celsius), is not where you’d expect to find an electric school bus.
But here is the No. 50 bus, with a cartoon horse decal on the side, leisurely traveling around 40 miles of snowy and icy roads each day in Tok, ferrying students to school not far from the Canadian border.
It works well on the daily route. But cold temperatures rob electric vehicle batteries of their travel range, so the No. 50 can’t make long trips to the field, or to Anchorage or Fairbanks.
It’s a problem some electric passenger vehicle owners and transit officials are encountering in cold climates around the world. At 20 degrees F (minus 7 C), EVs simply don’t go as far as they do at the ideal 70 degrees. Part of that is because keeping passengers warm using traditional technology drains the battery.
Longer journeys can therefore be difficult in very cold weather. Transit authorities like Chicago, which has pledged to convert its entire bus fleet to electric by 2040, must take extraordinary steps to keep electric buses charged and on schedule.
Some automakers and drivers worry that poor battery life in the cold could limit the acceptance of electric cars, trucks and buses, at a time when transport emissions need to drop sharply to fight climate change. There is hope. Scientists are racing to perfect new battery chemistries that don’t lose as much energy in cold weather as today’s lithium-ion systems.
In addition, cars equipped with efficient heat pumps lose less 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 reaches zero, his cost of running Tok’s electric bus doubles. Tok has one of the highest electricity prices in the country.
In the coldest weather, 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 around 90 cents a mile when it’s hot, but he says the costs make it unusable and he wouldn’t buy another one.
Many personal electric vehicle owners also find that long winter drives can be difficult. Electric vehicles can lose between 10% and 36% of their range, as cold spells occur 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 to 20 F (minus 7 to minus 12 C) range. “I typically see over 20% degradation in range as well as charging time,” he said while charging his Kia EV6 in a 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 range would decrease, so he said with planning, the Kia EV always gets it where it needs to go, even with a long drive.
Some owners, however, had not expected such a significant drop in winter. Rushit Bhimani, who lives in a suburb north of Detroit, said he sees around 30% less range in his Tesla Model Y when the weather gets colder, from what’s supposed to be 330 miles per charge to as low as 230. “They should clear that one up,” he said, charging 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 a lot of heat so they can travel farther, wearing gloves or sitting in heated seats to save energy.
And to be sure, gasoline engines can also lose about 15% of their range in cold weather.
The loss of range has not slowed the adoption of electric vehicles in Norway, where almost 80% of new vehicle sales were electric last year.
Recent tests by the Norwegian Automobile Federation revealed that the models really do vary. The relatively affordable Maxus Euniq6 came close to its advertised range and was named the winner. It only finished about 10% short of its advertised range of 220 miles (354 km). The Tesla S was about 16% below its advertised range. Bottom: Toyota’s BZ4X, which only achieved 323 kilometers (200 miles), almost 36% below its advertised range.
Nils Soedal of the Automobile Federation calls the problem “no problem” as long as drivers take it into account when planning a trip. “The big problem is really having enough charging stations along the road” and better information on how well they are working, he said.
Temperatures ranged from zero to minus 2.2 F (0 to minus 19 C) during the test, over mountains and along snow-covered roads. The cars were driven until they ran out of juice and came to a stop.
Recurrent, a US company that measures the battery life of used electric vehicles, said it conducted studies monitoring 7,000 vehicles remotely and found similar results to the Norwegian test.
CEO Scott Case said many electric vehicles use resistance heating for the interior. Those who are more successful use heat pumps.
Heat pumps draw heat from outside air, even in cold weather, and have been around for decades, but only recently have they been developed for automobiles, Case said. “It’s definitely what needs to be in all these cars,” he said.
Inside the batteries, lithium ions pass through a liquid electrolyte, producing electricity. But they travel slower through the electrolyte when it’s cold and don’t release as much energy. The same thing happens in reverse, which slows down the charge.
Neil Dasgupta, an associate professor of mechanical engineering and materials science at the University of Michigan, likens it to spreading cold butter on toast. “It just gets tougher at lower temperatures,” Dasgupta said.
General Motors is among those working on solutions. By testing, engineers can make changes to battery and heat management in existing cars and learn for future models, said Lawrence Ziehr, project manager for energy harvesting on GM electric vehicles. .
Last week, GM sent a squadron of Detroit-area electric vehicles to Michigan’s chilly Upper Peninsula to test the impact of cold weather on battery range.
Despite stopping twice to recharge along the way, a GMC Hummer pickup, with a range of about 329 miles per charge, made the 315-mile trip to Sault Ste. Marie with only about 35 miles remaining, barely enough to reach GM’s test facility. After finding a broken charging station in a grocery store, engineers drove to a nearby hotel to get enough juice to complete the trip.
At universities too, scientists are working on chemical changes that could make cold weather loss a thing of the past.
Dasgupta from the University of Michigan says they are developing new battery designs that allow ions to flow faster or allow fast charging in the cold. There are also battery chemistries such as solid state that do not use liquid electrolytes.
He expects the improvements to move from labs to vehicles over the next two to five years.
“There really is a global race to increase the performance of these batteries,” he said.
David Keyton contributed from Stockholm, Sweden. Krisher reported from Chicago and Sault Ste. Mary, Michigan.
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