Recently the New York Times and American electric car maker Tesla got in a highly publicized war of words over a review of the Model S electric car. Amongst other contentious issues, the range of the vehicle didn’t meet the Times’ writers expectations.
Tesla, as well as throngs of alternative fuel fans, were quick to point out that any hybrid or electric vehicle tested in the cold will suffer from lower performance.
Almost all batteries will suffer similar side effects in the cold, but unlike in your laptop or phone, the change in a car’s range could be the difference between making it to your destination… or waiting for AAA.
WHY DO EVS SUFFER IN THE COLD?
The simple explanation is that batteries use a chemical reaction to provide power. Chemical reactions are slower in the cold, and the battery doesn’t produce the same electrical current that it can at room temperature. As a result, EV batteries have to work harder as the mercury sinks, reducing range.
Each vehicle’s range will differ in the cold and it’s hard to pinpoint exactly what to expect when dealing with a cold vehicle and driving range. The folks at TheCarElectric.com, a Consumer Electronics Advisory Group website specializing in EV news and advice, say a change of 10 degrees Fahrenheit can sap 50 percent of a battery’s output.
All EV batteries suffer from these issues. Hybrids do too, though due to smaller batteries the issue isn’t as severe. Also, hybrids are able to use their gasoline engine to warm the electric components.
Automakers are currently developing similar ways to achieve the same result in purely electric cars. For example, the Nissan LEAF is equipped with a battery heater that activates to help the car turn on if left unplugged in the cold. Without it, the battery would get too cold and the car wouldn’t start. This battery heater kicks in only when the Leaf is left in extremely cold weather (around 14 degrees Fahrenheit) and uses minimal power to avoid draining the battery.
HVAC IS THE ENEMY
“Since battery range is much more important in fully electric vehicles like the Toyota RAV4 EV, we employ a number of HVAC strategies to help preserve driving range,” says Toyota spokeswoman Cindy Knight. “The RAV4 EV has a pre-conditioning system that can be activated before you get in to drive, while the car is still plugged in and using household electricity.”
That can be set up either through a smart-phone app that is registered with the vehicle, or through the car’s infotainment display. Furthermore, the RAV4 EV features a few different HVAC modes to help make the car comfortable without killing the battery. While a “Normal” mode works just what is expected in any other car, the “Eco-Lo” and “Eco-High” modes are far more conservative in regards to energy usage.
“Eco-Lo balances cabin comfort with range improvement,” says Knight. “The blower level is slightly reduced and the compressor and electric heater operate at lower levels to reduce power consumption.” Additionally, the driver’s seat warmer is activated automatically and adjusted. The other setting, Eco-High, is much more serious about saving energy. “Eco-High maximizes driving range at the expense of cabin comfort,” says Knight. “It reduces the blower, compressor, and heater levels and does not activate the seat heaters.”
By using these different modes instead of the normal mode, the range of the Toyota RAV4 EV increases by 18 percent in Eco-Lo, and 40 percent in Eco-High.
Other EVs have features just like these, including the Nissan Leaf.
“For 2013, Nissan will be equipping all Leafs with a new hybrid cabin heating system that will keep the cabin warm while using significantly less energy than previous models,” says Nissan spokesman Steve Yaegar. This change might not make a big impact on the EPAs tested range, but Yaegar is confident that it will make a difference in real-world driving.
OTHER TIPS FOR THE COLD
“Generally speaking, the less use of HVAC, the better,” says Daniel Gray of MPGomatic.com. Gray’s site slogan is “Burn Rubber, Not Gasoline” and the site has a focus on fuel-friendly vehicles. He offered some tips on how to keep an EV going in colder weather.
“The defroster is a double-whammy, because it turns on the A/C,” he says. The best practice, according to Gray, is to turn it on, defrost and defog, then use it sparingly. Gray also advises owners to keep their car in a garage if possible.
In order to reduce the reliance on the HVAC systems, many EVs have seat warmers, and drivers are encouraged to use them.
“Seat heaters are much more efficient and faster at warming the driver and passenger than blasting the HVAC” says Knight.
CALCULATING THE COLD
It’s important to recognize that all EVs are sensitive to cold weather, and are going to suffer from reduced range in those conditions. Through new innovations and owner initiative there are ways to reduce the impact, but if you’re considering buying an EV for daily driving, and live in an area where it gets really cold, you may not find the vehicle’s range enough when the winter weather hits.