In hindsight, it’s not surprising the Mitsubishi MiEV EV I drove barely made it to 50 miles rather than its rated 62 miles (100 km). It was a dark and chilly if not stormy early December night and that killed the range. When you drive an EV, “your mileage may vary” includes cold weather as well as hard acceleration and late braking. As temperatures dip below freezing, you could lose 25% of your electric vehicle’s precious range. Batteries are less efficient in cold weather, they don’t regenerate as well, and electric heating for the cabin, seats, and windows drains your range, too.
The same thing happened when I drove a Tesla Model S. With the 85 kWh battery, the Tesla is good for around 250 miles. During the afternoon with temperatures above freezing, the discharge rate indicated I wasn’t far off from that kind of efficiency. Driving at night as temperatures fell into the 20s (0C to -5C), I found the range fell noticeably faster than the distance gauge suggested at the start of the trip.
None of this should be surprising. The 12-volt batteries on mainstream cars are prone to failure in the first cold weeks of winter. A battery is a chemical reaction that gives off electrons, or power. When it’s cold, the reaction slows down in both directions, discharging and charging. See, there was a reason to pay attention in chemistry class. You can keep a chemical reaction going by applying heat, which is one way to get more energy out of a battery — but that can be a complex equation, if the energy to heat the battery comes from the battery itself.
How cold weather affects EV range
A cold battery is not as receptive to regeneration. Trying to charge at the same rate that’s possible during warm weather can shorten the battery’s life. The Nissan Leaf uses an electric heater to keep the battery warm; the energy comes from the battery, although the energy expended to heat the battery is outweighed by the additional power that becomes available. Tesla uses waste heat generated by the electric motor. It’s efficient once there’s waste heat available but that takes time.
There’s even more drain from cockpit-warming: using electric heat in the cabin, on the seats, and defrosting the front and bind windshields. Combustion engine cars give off enough waste heat to quickly warm the cockpit without hurting range. In both the MiEV and Tesla, as I saw range dropping, I dialed back the heat and put on a parka and gloves.
Researchers are looking into different battery electrolytes that would be conducive to quick charging without compromising conductivity. EV makers could also make thicker, less conductive window glass and better insulate the car. Both would also reduce road noise.
How to maximize the range of your EV
If you have a garage, park your EV there since it’s warmer than outside. Arrange charging to continue until you’re ready to leave. Use the preheat functions while the car is still connected to the charger; most EVs offer that as a feature of their smartphone apps.
If you can stand it, turn off the heat while driving, or dial it back. A fleece jacket and thin gloves are your friends. Even the infotainment system draws power and I’ve been in EVs that wanted to power down the head unit to conserve power. With its small battery pack, the MiEV was especially susceptible to the cold.
Cold weather is also the reason to consider ordering the extended range battery pack, even if it adds $ 10,000 or more to the price of your EV. Better you get nicked once by the price and enjoy longer driving distances than you remember all the little compromises made regularly to keep your EV going.
The problem of cold cars has existed for years. Air-cooled Volkswagens and Porsches took longer to heat the cabin than cars with water-cooled engines. The air-cooled cars used a heat exchanger wrapped around the exhaust pipe. Heat took a long time to arrive and when the heat exchangers weren’t perfectly sealed, the smell of exhaust gas and burning engine oil might invade the cockpit.