Electric Car Range in Cold Weather

http://www.motherearthnews.com/green-transportation/electric-car-range-in-cold-weather-zb0z1204zmat.aspx

Electric Car Range In Cold WeatherWhere I live, we have bitterly cold winters. I’ve been told that electric cars don’t handle cold weather well. Is that true? Do some models do better than others?  

Electric car battery range is better in warmer climes, because in cold weather, chemical reactions happen more slowly. A drop of just 10 degrees Fahrenheit can sap 20 to 50 percent of a battery’s charge, depending on the system. According to Sherif Markaby, who directs Ford’s electrification program, batteries “are similar to people, as they both achieve maximum performance working under moderate, unchanged temperatures.” A warm battery can better accept charging from the regenerative braking system. Ford (for the Focus Electric) and GM (for the Volt) address this problem with a liquid temperature management system, which warms the battery pack as the car is charging. 

I drove the Volt during a chilly week in the cold winter of 2011, and traveled 28 miles before the gas engine kicked on to recharge the batteries. The Volt’s standard range is estimated to be 35 miles before it switches to gas power. 

Tony Williams, a San Diego-based Nissan Leaf owner, has created a range chart (see it at My Nissan Leaf) that is proving quite useful to other drivers of the all-electric car. According to Williams, at 70 degrees Fahrenheit, a Nissan Leaf with a full charge traveling at 55 mph will have 89 miles of range. But — and this is just one person’s experience — Williams’ calculations show that the car will lose 1 percent of range for every 2 degrees the temperature drops. For many drivers, that would translate into only 65 miles of real range available during a cold winter. 

Electric car battery range and performance isn’t the only issue in cold weather: Electric cars don’t have alternators to generate electricity. That means that the heater is a direct drain on the batteries — almost as dramatic as the drive motor itself. According to Williams, the Leaf’s heater can draw 1.5 to 3 kilowatt-hours (kwh) of electricity in an hour of use, and that’s a big dent when the battery stores only 24 kwh. 

Nissan estimates that at 14 degrees with the heater running, the Leaf’s range is 62 miles. 

Automakers are working on these problems. Their approach looks like a stopgap until a more efficient cabin heater is developed. Nissan introduced a standard cold-weather package for the 2012 Leaf that aims to reduce use of the climate control system with heated seats, a duct to direct warmth to the back seat, temperature management for the battery, and heated steering wheel and mirrors. Volt and Leaf owners can help their range by pre-warming the battery and the cabin while the car is plugged in . 

Patrick Wang, a Volt owner in the San Francisco area, saw his 40 miles of range drop to 34 miles when the temperature hit 40 degrees in northern California. His cold-weather driving tips include reducing cabin temperature to 68 and running the gas engine to warm up the cabin, then reverting to electric mode with the heater set to low. 

— Jim Motavalli, Author of High Voltage: The Fast Track to Plug In the Auto Industry

Photo courtesy Tesla Motors