Lately, Tesla has been keen to emphasize the performance of its cars on snow and ice, tweeting out a video of the Model 3 swashbuckling about a winter proving grounds and running a promotion in which customers can win the chance to drive on a frozen sea in Finland. Elon Musk is right to show that electric motors and their digital controls can provide great traction and control, but EV drivers have other factors to consider in winter weather: How far they can go, and how long it will take them to recharge.
Cold temperatures can hurt both, especially when it gets as severe as Winter Storm Jaden, which has triggered states of emergency across the country and will subject more than 70 percent of the US population to subzero temperatures over the next few days. That’s because the lithium-ion batteries that power EVs (as well as cellphones and laptops) are very temperature sensitive.
“Batteries are like humans,” says Anna Stefanopoulou, director of the University of Michigan’s Energy Institute. They prefer the same sort of temperature range that people do. Anything below 40 or above 115 degrees Fahrenheit and they’re not going to deliver their peak performance. They like to be around 60 to 80 degrees. As the temperature drops, the electrolyte fluid inside the battery cells becomes more sluggish. “You don’t have as much power when you want to discharge,” says Stefanopoulou. “The situation is even more limited when you want to charge.”
Modern cars are designed to take that into account, with battery thermal management systems that warm or cool a battery. But while an internal combustion engine generates its own heat, which warms the engine and the car occupants, an EV has to find that warmth somewhere else, either scavenging the small amount of heat that motors and inverters make or running a heater. That takes energy, meaning there’s less power available to move the wheels.
Additionally, to protect the battery—the most expensive component of an EV—the onboard computer may limit how it’s used in extreme low temperatures. The Tesla Model S owners manual warns: “In cold weather, some of the stored energy in the Battery may not be available on your drive because the battery is too cold.” Tesla adds a snowflake icon next to the range indicator to show it might be impacted. Typically, an EV will cover around 20 percent fewer miles in cold weather versus beach weather.
When it comes to putting electrons into the battery, freezing weather hurts in two regards. It limits regenerative braking, so the car recoups less power and drivers can’t rely on one-pedal driving. And charging, particularly fast charging, will be limited to protect the battery. Experienced EV owners are well used to these quirks, but forums show new EV buyers are still struggling with them.
Don’t despair—there are workarounds. First, don’t let the battery get too low—make sure you always have a 20 percent charge or so. If you want to power up in subzero temperatures, the car may need that reserve to warm the battery enough to start the process. “Don’t think that being near an outlet to charge will get you out of trouble,” Stefanopoulou says. And when you are plugged in, take advantage of that power supply to precondition the car, warming both the interior and the battery, before zooming off. Vehicles like Teslas, and the new Jaguar I-Pace electric, will let you do that from afar via an app.
Meanwhile, researchers like Stefanopoulou are working on smart solutions to maximize the cold weather coping capacity of cars. If the navigation system is programmed to head to a fast charger, the computer can make sure the battery is nice and warm by the time it arrives there. And in a recent paper, Stefanopoulou suggests a battery could discharge some of its precious energy when it’s cold, to keep itself warm. That sounds counterintuitive when range is already limited, but driving on a cold battery, with high resistance, when current demands to the motors are also high, is more wasteful.
In the longer term, scientists are working on solid state batteries that don’t have liquid inside and won’t be so sensitive. But they’re still at the lab stage, so figure five to 10 years before you get to see one in your garage. But by adding some smarts, researchers are figuring out how to make EVs as predictable and drama free as possible to own, “so we can remove last bits of customer acceptance issues,” says Stefanopoulou. Meaning drivers can get their adrenaline highs from the icy lake course, instead of the plunging range meter.