Range of electric cars cut in cold, hot weather

The range of electric vehiclescan be greatly reduced, by up to 57% , depending on the temperature outside, auto club AAA says.

The AAA Automotive Research Center in Southern California found that the average range of an electric car dropped 57% in very cold weather – at 20 degrees Fahrenheit – and by 33% in extreme heat, a temperature of 95 degrees.

"We expected degradation in the range of vehicles in both cold and hot climates, but we did not expect the degradation we saw," said Greg Brannon, AAA's director of automotive engineering.

AAA conducted a simulation to measure the driving range of three fully-electric vehicles – a 2013 Nissan Leaf, a 2012 Mitsubishi iMIEV and a 2014 Ford Focus Electric Vehicle – in cold, moderate and hot weather. It tested the vehicles for city driving to mimic stop-and-go traffic between December and January, fully charging each EV, and then "driving" each on a dynamometer in a climate-controlled room until the battery was fully exhausted.

Brannon said two of the vehicles, the Mitsubishi and the Ford, were equipped with dedicated management of the battery temperature. "We were expecting that difference would yield differences in the optimal range of the vehicles in extreme temperatures," he said. "It did not."

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The likely reason: There's only once source of power in an electric vehicle – the battery. If battery power is being used to heat or cool the battery, it takes power away from the vehicle's range, he said.

The average electric vehicle battery range for each full charge in AAA's test was 105 miles at 75 degrees Fahrenheit. That dropped 57% to 43 miles when the temperature was held steady at 20 degrees. Warm temperatures were not as stressful but still delivered a lower average of 69 miles per full charge at 95 degrees, AAA said.

The three vehicles chosen were selected because they're the most wi! dely available electric cars in the USA, Brannon said. "For most Americans, where a round-trip commute is less than 40 miles, the range of the vehicle will not be a problem," he said. "However, if the temperature dips down and you want to take a drive to grandma's house, you might want to think about a charging station along the way."

Among AAA's recommendations: storing the electric car in a garage; monitoring recharge times in colder weather; preheating or cooling the car while it's plugged in to reduce battery drain, and using electric seat heaters to keep warm.

USA TODAY was unable to reach the carmakers for comment.