By Paul Homewood
Hoping to increase the appeal of their battery-electric vehicles, automakers have begun rolling out an assortment of "long-range" models, such as the Tesla Model 3, Chevrolet Bolt EV, Jaguar I-Pace and Nissan Leaf Plus.
Under ideal conditions, these products can deliver more than 200 miles per charge and, in some cases, even 300. But as many owners discovered last week as winter storms slammed much of the country, cold weather conditions do not qualify as "ideal." A new AAA study finds that when the thermometer drops to 20 degrees Fahrenheit, range falls by an average of 41 percent on the five models it tested.
"We found that the impact of temperature on EVs is significantly more than we expected," said Greg Brannon, AAA’s director of Automotive Engineering."
Some EV drivers — including this correspondent — recently found that range can drop by half when the mercury tumbled into negative territory. But the AAA study appears to be the first to have used standard, repeatable methodology to confirm the problem and compare the effect of winter temperatures on different models.
There were several surprises that emerged from the research, according to Brannon, starting with the fact that the impact on range was pretty much uniform among all five of the battery-electric vehicles AAA tested: the BMW i3s, the Chevrolet Bolt EV, the Nissan Leaf, the Tesla Model S and the Volkswagen e-Golf.
"It’s something all automakers are going to have to deal with as they push for further EV deployment because it’s something that could surprise consumers," said Brannon.
Different factors can affect the loss of range, he and other experts have noted. Simply turning on the electric vehicles, or EVs, AAA studied in 20 degree weather revealed a 12 percent loss in range. On a vehicle like the Chevy Bolt, with an EPA rating of 238 miles per charge, that would drop range to 209 miles. But that part of the test assumed operating the vehicle with neither cabin heat or even seat-heaters turned on.
Using climate control revealed an even bigger surprise, according to Brannon, as range dipped by an average 41 percent — which would bring an EV like the Bolt down to just 140 miles of range.
The problem is that unlike a car with an internal combustion engine that can warm the cabin with waste heat, EVs have to tape into their batteries to power the climate control system.
Part of the problem, said the AAA director, is that "lithium-ion batteries like the same sort of temperatures that we do, around 70 degrees."
Much below that and the chemistry used to store energy runs into various problems. Among other things, battery components develop increased resistance that limits how much power they can hold, as well as how fast a battery pack can be charged or discharged, explained Timothy Grewe, chief enginer for electric propulsion systems at General Motors.
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February 8, 2019 at 04:48AM