Chevy Volt in Winter
Luke Ottaway's picture

EV Battery degradation in extreme temperatures might not be as bad as AAA says

AAA announced yesterday that electric vehicle range is significantly reduced in hot and cold weather. However, their tests are no substitute for real-world data.

It is well-known that the performance of lithium-ion batteries is affected by temperature. The AAA Automotive Research Center set out to find out the extent of these thermal effects by testing three popular electric vehicles: the Nissan Leaf, Ford Focus, and Mitsubishi iMIEV. What they found was rather unfortunate for supporters of EVs.

The test vehicles were driven on a dynamometer simulating city driving conditions in a climate-controlled room at 20 degrees, 75 degrees, and 95 degrees Fahrenheit. The average range of the vehicles was 105 miles at 75 degrees, but it dropped a shocking 57% to just 43 miles at 20 degrees and 33% to 69 miles at 95 degrees. According to Greg Brannon, the director of automotive engineering at AAA, "We expected degradation in the range of vehicles in both cold and hot climates, but we did not expect the degradation we saw."

Don’t hit the panic button just yet. It is known that cold and hot weather shorten EV range – below about 68 degrees Fahrenheit, battery life decreases linearly with temperature. Some Leaf drivers in extremely hot climates, particularly Arizona, have seen drastic drops in range due to the air-cooled battery of older and current Leaf models. Nissan is addressing this issue. However, cold and hot weather performance depend on many factors and vary in the real world. Driving style and use of heating or air conditioning significantly impact range.

Back in December, Green Car Reports published data from FleetCarma, a company that tracks data from fleet managers and private owners. They monitored more than 7,000 Nissan Leaf trips to determine real-world range and found that the average range at 25 degrees Fahrenheit was approximately 60 miles, or about a 21% drop from the ideal range of 76 miles. Even at 0 degrees the average range was still only 37% less than ideal at 48 miles. With temperatures of 95 degrees, the average Leaf range was about 56 miles, or a 26% drop from the range at ideal temperatures between 60 and 75 degrees Fahrenheit.

In short, there is no substitute for real-world data. AAA may have done the best they could to simulate actual results, but they did not release information about the use of climate control within the vehicles and used the EPA’s “stop-and-go” drive cycle, which appears to mean the UDDS cycle that represents one out of five cycles that the EPA uses to officially calculate estimated range. And as all EV drivers know, driving style affects that number significantly as do features like heated seats that use less energy than a conventional heater.

So take note of AAA’s results, and be mindful of the effect of temperature on your vehicle’s range if you own an EV. But every vehicle’s battery is different and everybody’s driving habits are different, so it would be more helpful to track your vehicle’s range yourself.

If you own an electric vehicle, what is your experience in extreme weather? Let us know in the comments section.

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Comments

Greetings Luke. Could you please expand a bit as to the how's and why's of battery charge rate, storage capacity and why the stored energy retention drops in cold weather? I do know that in my decade of living off grid ( Solar Panels, Trace Inverter,Trojan Deep Cell Battery, controller and 3 phase diesel generator:) my storage " charge" retention halved in winter weather condition; Despite the batteries being temperature controlled( to a certain extent.) A bit of science? Thanks.
I believe that it has mostly to do with the rate at which the chemical reactions can occur. Since the electricity is released via movement of electrons through the electrolyte from one electrode to the other (the electrons are produced from the aforementioned chemical reactions), when the temperature drops the chemical reactions don't occur as quickly and reduce current carrying capacity. The name for this phenomenon is the Arrhenius Law. With reduced power output, the vehicle demands cause the battery to work harder and reduce its capacity.
Perhaps Arrhenius resided in warmer climes. Seriously folks. As recommended by all battery and EV manufacturers garage your car in the winter.
Well, even if you garage your car, you still have to drive on streets and highways that are going to be at ambient temps. An acquaintance of mine who is into EV's and plug-ins (a Leaf and several Honda Insights) will leave his Leaf parked during the winter because the range is significantly diminished. He lives out in the country.
I discussed those FleetCarma results here on TN as well. Lively topic. http://www.torquenews.com/1080/new-data-canada-shows-cold-weather-range-loss-nissan-leaf-and-chevrolet-volt
The 2013 LEAF has a very efficient Heat Pump for cooling and heat. When I compare our 2013 Focus to the LEAF the Focus uses 3-4 times more energy than our LEAF and cuts range much more with climate control on here in the Phoenix area. The LEAF has the most efficient Heat Pump I have seen. Heat shortens the life of a battery of any kind. So Nissan has a new Desert battery I like to call the Lizard battery that can take the heat with no cooling and have long life. It should be released in about April of 2014.
This owner of a 2015 Leaf would note that the heat-pump AC is not standard on the base S. We bought the vehicle used (lease turn-in? with 14,500 miles), and it has an inefficient compressor AC and non-LED head-lights.
Everyone should know AAA belongs to the AAAMA with big auto and has tried to stop nearly every car advance like seat belts, better bumpers, etc for 5+ decades. They should not be a source of info because they have proved they can't be trusted. Winter range reducing in EV's is about the same as gas cars. Facts are drag load like tires, diff lube, etc go way up in cold weather. As for heating, cooling loads EV's are pre heated, cooled before you get in them lowers the energy needed plus you are not in the EV long enough to use much power for these. Facts are in winter EV's are more reliable than trying to start a gas car that then has a while to warm up making it's worse pollution, mileage/fuel waste. Just that energy in an EV likely get you all the way to work!!