Alliy Sahagan coasted in a 2017 Nissan Leaf into the Gunnison County Electric Association (GCEA) warehouse in Gunnison, Colo. on the electric vehicle equivalent of running on fumes. Just minutes earlier, the Leaf’s dashboard told her the car had zero miles left and a 9% battery charge.

Sahagan was returning from what was supposed to be a 25-mile test drive on a minus 5-degrees Fahrenheit January morning. When she left the electric utility company’s warehouse, she didn’t notice the battery level was at 63%.

Sahagan knew GCEA operating guidelines warn battery electric vehicle (BEV) operators to expect up to a 40% reduction in vehicle range in Gunnison’s subzero winter weather.

“In my haste, I neglected to follow some of my own EV prep preaching,” says Sahagan, who oversees the association’s BEV loan program, which includes the Leaf, a Chevy Spark model and two other hybrid-electric vehicles.

She has since used this story as a cautionary tale to help people remember the dos and don’ts of operating electric vehicles during the winter.

Battery Science

According to the University of Michigan’s Energy Institute, the batteries on electric vehicles are much like human beings — they prefer the same temperature range of 60 to 80 degrees for optimal performance. As a result, charging should take place at temperatures above freezing.

As the temperature drops, the battery’s electrolyte fluid flows more sluggishly. At temperatures below freezing, charging the battery without first reducing the charge current causes the battery to become less mechanically stable and more prone to sudden failure, warns RELiON manufacturer of a low-temperature lithium iron phosphate battery.

According to RELiON, under normal conditions, the battery’s lithium ions are soaked up by the porous graphite in the anode, or negative terminal, much how a sponge soaks up water.

Below freezing, however, the anode doesn’t efficiently capture the lithium ions. Instead, many lithium ions coat the surface of the anode, restricting the flow of electricity and causing the battery’s capacity to drop.

Low Temp Advice

For BEV operators, these recommendations will help maximize performance and range:

• Always use a battery management system to recharge an electric vehicle battery, particularly during extreme cold and hot weather. The system will protect the battery from damage by appropriately regulating the charge rate in extreme temperatures.

• Whenever possible, avoid running an electric vehicle below 20% charge, particularly in winter. Unless you can warm up the battery using a block heater or parking in a heated garage, the BEV may need that power to warm itself up to where it can accept a charge.

• Use an application associated with publicly available charging stations to locate them along your route to recharge the battery.

• Remember that most charging stations are designated Level 2, which means it could take up to several hours to get a full charge. Need a faster charge? Look for “DC fast charge” or Level 3 charging stations. While few in numbers at this stage, these stations can recharge batteries in as little as 30 minutes.

• Wind speed can also greatly impact BEV range.

• When the battery is low, or the vehicle isn’t running, be sure to limit the use of or shut off unnecessary accessories that will continue to drain the battery and reduce range.

• The capacity of BEVs to receive charges can vary, particularly in extreme temperatures, which will affect recharge times.