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Electric vehicles and winter weather

Nissan Leaf and Chevrolet Volt
Nissan Leaf and Chevrolet VoltNissan and General Motors

Plug-in electric vehicles like the Nissan Leaf and Chevrolet Volt have been getting a great deal of attention recently but one thing we haven't seen much of is images of EVs in winter weather. There is a good reason for that, electric vehicles can suffer a significant range reduction in cold weather.

Even the most advanced lithium ion batteries available today have only a tiny fraction of the energy density available from a gallon of liquid fuel like gasoline or diesel. That's why the 660 pound, 24 kilowatt-hour battery in the Leaf can barely provide the same roughly 100 mile range as about 20 pounds (approximately three gallons) of gasoline. The smaller 16 kWh (of which 10.6 kWh is usable) battery in the Volt offers about 25-50 miles of electric driving depending on the conditions.

Fuel economy has always been widely variable depending on the driving conditions and driving style and that is particularly true for EVs. Every major automaker producing an EV acknowledges that range will drop in cold weather. The question is why?

While internal combustion vehicles consume more fuel in cold weather for a number of reasons including increased aerodynamic drag from the low temperatures, no matter what the temperature, an engine always produces a lot of waste heat. The coolant used to manage engine temperatures always flows through a heat exchanger. When the mercury dips and drivers turn up the interior temperature, a flap is opened that allows air to flow through the heat exchanger and warm up. Other than the electrical load from a ventilation fan, there isn't any significant additional load on the engine when heating the car and fuel economy isn't really affected.

An electric vehicle on the other hand doesn't have this source of "free heat energy" (insofar as wasted energy can be considered free) so it has to use an electric resistance heating system. That heating system is drawing power directly from the battery and in turn reducing the driving range. In cold weather it can take about as much energy from the battery to heat the cabin as it does to propel the car at constant speed. That's why GM lists the Volt range as low as 25 miles in cold weather and as high as 50 miles in more moderate conditions. Similarly Nissan acknowledges that winter driving will bring the Leaf range down to the low 60 mile region.

Automakers have taken a number of steps to mitigate this problem but it will never go away completely. The Volt comes standard with heated seats because it takes significantly less energy to keep passengers comfortable when the heat is transferred directly to their backsides than it does to warm the entire cabin. Both the Leaf and Volt also feature the ability to preheat the car on a timer while it still plugged in to charge, thus using power from the grid and keeping the battery full. It takes less energy to maintain the temperature than it does to heat it up.

Electric vehicles still work very well in cold weather, they just can't do it as long and they will suffer more in terms of range than a traditional internal combustion engine vehicle.

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