If you plan to drive an EV in winter weather you’ll need to charge more often to avoid “being stranded by a dead battery.”
So sums AAA about its report on electric vehicle range, released this past week, which resulted in a very useful data set underscoring the reality of how EV range drops, especially at cold temperatures. As the organization concludes, on average, a 100-mile range at 75 degrees will drop down to just 59 miles on a 20-degree day, or 83 miles on a 95-degree day.
The organization however fumbles some of the broad takeaways for would-be electric-vehicle shoppers, using that fear-inspiring takeaway—the “stranded” part of course being what local news reports around the country have picked up on in recent days.
AAA should know better, as the messaging is out of sync with trends the organization itself noted in 2016. It had invested in a fleet of emergency roadside fast-charging-capable trucks, and then admitted, from its experiences over several years, that EV owners were seldom getting stranded, no matter what the time of year.
With the average round-trip commute somewhere around 32 miles, and most of today’s popular electric vehicles now offering an EPA-rated range of more than 100 miles, we see this realization as something that’s useful to know, but mostly moot.
Yes, you’ll have to plug in more often in the winter. Factors that come into play in range include the temperature of the battery, the interior temperature, driving habits, and the type of driving conditions. You grow to understand those quite soon after owning an electric vehicle.
Factors contributing to EV range - 2019 AAA study
AAA did however have some useful advice for EV owners before hitting the road: Make time to heat or cool the vehicle ahead of time (or park in a garage), and plan ahead. It added that those in mild or warm-weather places shouldn’t be discouraged.
The one thing AAA forgot to do is contextualize this against internal-combustion engines, which lose efficiency (and range) at lower temps, too—and thus they’re also more expensive to run in the cold. As put by the EPA: “Fuel economy tests show that, in short-trip city driving, a conventional gasoline car's gas mileage is about 12 percent lower at 20 degrees F than it would be at 77 degrees F. It can drop as much as 22 percent for very short trips (3 to 4 miles).”
As for why there’s such a drop in range from ICE to EV vehicles in cold weather, think of it this way: With internal combustion engines, we’re used to pre-paying for heat that we might or might not use. With electric vehicles, we save a lot, potentially, and the cabin warming is strictly optional.
In short, it amounts to a double-whammy: Electric-car batteries are adversely affected by temperature extremes, especially cold. And EV climate control systems significantly ramp up energy use.
Four EVs, many driving cycles
The research itself was done in partnership with the Automobile Club of Southern California’s Automotive Research Center (ARC) in Los Angeles, with the results based on those from a 2018 BMW i3s, 2018 Chevrolet Bolt, 2018 Nissan Leaf, 2017 Tesla Model S 75D, and 2017 Volkswagen e-Golf.
The study only tested one vehicle model per manufacturer, and it chose the specific vehicles for having an EPA-estimated range of 100 miles or more.
AAA conducted its range test in accordance with SAE J1634, at ambient temperatures of 20, 75, and 95 degrees F, running the vehicles in a closed facility and dynamometer, through a sequence of standard federal driving cycles, and included instrumented dynamometer and road-load factors. The vehicles were “soaked” at a new temperature for at least four hours before any testing, but it started each test within an hour of the cars being removed from charge.
It’s smart that AAA separated out range and efficiency, as at different temperatures the actual energy capacity of the battery can change.
The cold reality
It found that an ambient temperature of 20 degrees resulted in a 12-percent decrease in driving range and a 9-percent decrease in energy efficiency [actually MPGe, which we'll spare you from in this piece]. At 95 degrees there was a 4-percent decrease in range and a 5-percent decrease in energy efficiency.
The effects of those temperature extremes—especially cold—were greatly exaggerated with the use of climate control. The use of the heater at 20 degrees resulted in a 41-percent drop in range and a 39-percent reduction in energy efficiency, versus 75 degrees, and the 95-degree test showed a 17-percent drop in range and 18-percent drop in energy efficiency.
Percent change in combined range - 2019 AAA EV range study
Of the four cars, the i3s and Leaf included a heat-pump system for heating, with resistive heating for very cold conditions—although AAA noted that at 20 degrees, the resistive heating was likely utilized.
Across the battery of tests, it was the Nissan Leaf that was the least affected by that most taxing task (driving in 20-degree temps with the heat on), while the heat pump didn’t seem to help the BMW i3 as it was the most affected. At 20 degrees, the i3s range was reduced by 50 percent and combined MPGe efficiency was reduced by 46 percent.
2017 BMW i3 electric car during winter snow storm [photo: owner Chris Neff]
The study even dug into what each automaker says in the owner’s manual about hot and cold environments, finding some useful nuggets of good practice. For example, the Bolt EV’s manual noted: “Keep the vehicle plugged in, even when fully charged, to keep the battery temperature ready for the next drive. This is important when outside temperatures are extremely hot or cold.”
The Model S manual notes that for better long-term performance you should “avoid exposing Model S to ambient temperatures above 140 degrees F (60 degrees C) or below -22 degrees F (-30 degrees C) for more than 24 hours at a time.”
Absolute zero for EVs
Although some of what's in the AAA report feels akin to crying wolf, over a reality that owners will come to understand, there may be one crisis that the Polar Vortex narrowly missed. Chicago, our third most populous city, dropped to a record low of -23 on January 30, the week before its annual auto show. That same week, the National Weather service noted that big city had gone for 52 straight hours below 0 degrees F.
It’s weather that, by the numbers, comes close to what even manufacturers admit is downright disabling to electric vehicles. In the owner’s manual for the e-Golf, Volkswagen warns, for instance, that its battery will freeze and not be functional at all if left for two days at temps colder than -13 degrees F.
At an event last week adjacent to the Chicago Auto Show, Matthew Renna, Volkswagen’s vice president for e-mobility for North America, explained to Green Car Reports that while the team bringing VW’s MEB vehicles to market had looked at the possibility of offering battery chemistries that varied by market, they were for the most part faced with the reality that within each of the world’s major markets there’s a lot of temperature variance—and the automaker, for instance, doesn’t have any control over whether a Florida car is brought to Alaska.
The best-known instance of an automaker working quickly to change its battery chemistry to match real-world performance (and temperatures) came some years back, when Nissan Leaf battery packs in hot-temperature climates were both dramatically under-delivering on range and degrading rapidly. To answer that, Nissan introduced its so-called “lizard” battery for that, throughout the U.S.
To date, we’re not aware of an example in which an automaker saw how poor its cold-weather battery performance was and ordered some changes. Although after this winter—and this study—there’s definitely precedent for that.