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AAA: EV HVAC use in frigid temperatures causes substantial drop in range

New research from AAA finds that when the outside temperature hits 20°F (-6.7 ˚C) and the HVAC system is used to heat the inside of an electric vehicle, the average driving range is decreased by 41%. This means for every 100 miles of combined urban/highway driving, the range at 20°F would be reduced to 59 miles.

AAA conducted primary research to understand the effects of ambient temperature on the range and equivalent fuel economy of five battery electric vehicles (BEVs) sold throughout the United States: the BMW i3, Chevrolet Bolt, Nissan LEAF, Tesla Model S 75D and the Volkswagen e-Golf.

Testing was performed according to guidelines established in SAE International standard J1634, Battery Electric Vehicle Energy Consumption and Range Test Procedure. Evaluated ambient temperatures included 20°F, 75°F and 95°F.

Key findings included:

  • In isolation, hot and cold ambient temperatures resulted in modest reductions of driving range and equivalent fuel economy. Driving range and equivalent fuel economy reductions slightly differ due to the temperature dependency of both the recharge allocation factor (RAF) and battery discharge capacity.

    • On average, an ambient temperature of 20°F resulted in a 12 percent decrease of combined driving range and a 9 percent decrease of combined equivalent fuel economy (when compared to testing conducted at 75°F).

    • On average, an ambient temperature of 95°F resulted in a 4 percent decrease of combined driving range and a 5 percent decrease of combined equivalent fuel economy (when compared to testing conducted at 75°F).

  • HVAC use results in significant reductions of driving range and equivalent fuel economy.

    • On average, HVAC use at 20°F resulted in a 41 percent decrease of combined driving range and a 39 percent decrease of combined equivalent fuel economy (when compared to testing conducted at 75°F).

    • On average, an ambient temperature of 95°F resulted in a 17 percent decrease of combined driving range and an 18 percent decrease of combined equivalent fuel economy (when compared to testing conducted at 75°F).

  • Depending on ambient temperature, HVAC use results in a significant monetary cost increase. For example, the study found that the use of heat when it’s 20°F outside adds almost $25 more for every 1,000 miles when compared to the cost of combined urban and highway driving at 75°F.

Thus, when colder temperatures hit, AAA urges electric vehicle owners to be aware of a reduction in range and the need to charge more often to minimize the chance of being stranded by a dead battery.

The appeal of electric vehicles continues to grow since a greater variety of designs and options with increased range have come onto the market. As long as drivers understand that there are limitations when operating electric vehicles in more extreme climates, they are less likely to be caught off guard by an unexpected drop in driving range.

—Greg Brannon, AAA’s director of Automotive Engineering and Industry Relations

The research clearly shows that electric vehicles thrive in more moderate climates, except the reality is most Americans live in an area where temperature fluctuates. Automakers are continually making advances to improve range, but with this information, drivers will be more aware of the impacts varying weather conditions can have on their electric vehicles.

—Megan McKernan, manager of Automotive Research Center

Previous AAA research has found that interest in electric vehicles continues to gain momentum with 20 percent of drivers saying they would likely go green when considering their next vehicle purchase. With lower-than-average ownership costs, increased driving ranges and the latest advanced safety features, AAA believes there is a strong future for electric vehicles.

To help “green” car shoppers make an informed choice, AAA conducts independent, rigorous test-track evaluations of plug-in hybrids, hybrid and fuel-efficient, gas-powered vehicles and releases the results every spring in its annual Green Car Guide.

Comments

mahonj

EVs in cold places should have small diesel or kerosene heaters.
This might sound retrogressive, but it is reasonable because while the efficiency of an ICE engine can be 20-35% (or less) in real use, a simple heater can be 90% efficient.
All you are trying to do is generate heat form an energy rich source - shouldn't be that hard.
Electric engines are so efficient that there is very little waste heat to be used to heat the cabin, hence the use of a diesel fuelled heater.
You wouldn't need to worry about catalysts or NOx reduction because you should be able to burn it cleanly if you don't need to create explosions.

Arnold


Metho burner (as long as the flames aren't too distracting) ? Reminiscent of the solid fuel or 12v glove warmers used by motorcyclists and heated suits for aeronautical.
Several designs that target heating zones have shown substantial energy savings.
Alternatively a cold weather cabin baffle might be a viable option or accessory especially as we now see rear vision mirrors replaced by camera and crazy as it may seem even forward vision need not be through glass.

While high efficiencies are accompanied by low heat losses I wonder if the same battery and motor cooling circuits cannot economically supply sufficient or at least supplementary heat even though those systems have their own preferred temperature range.

Herman

Not new news to most of us, and the reason I ditched an early ~75mi EV (that I loved) and switched to a PHEV. 38 miles doesn't get you much usefulness when there's no backup, no charger handy late-Dec through March bad days.

The reailty of EV life for most current US owners (read: west-cosaters, where the majority live) is temperate climate, a greater-than-normal garageful of cars from which to choose, and destination charging in many places. There really isn't much concern, hot or cold days. But it's an unwelcome surprise for less-aware folks who've tried to make a 1-2 car family switch to BEV's living in colder climes with less-developed charging infrastructure. Really, if car-sharing were as imminent as it's touted, this problem could be solved sooner than the Advanced Battery of Tomorrow in places where 1-2 months of chill limits utility of EVs.

Having said that:
If you're burning enough fuel to provide heat, you could burn a little more and generate power from an ICE to supplement the battery. (See: ERDTT)

MJ Grieve / AHEAD Energy 501c3

A small, near-zero emission APU is a huge enabler for practical EVs in sub-freezing weather. The key questions are: what fuel? and what APU technology? I’d argue for Propane/DME/Ammonia as a trio of low pressure gaseous fuels - based on no evaporative emissions, low cost tank and refueling infrastructure, long shelf life and near zero emission potential (both in burner modes and CHP modes). Ammonia is the zero carbon emission option, of course. For larger APUs, a small high CR internal combustion engine can target 45% fuel to electric efficiency. For very small APUs for urban cars, a small SOFC (5-15 kW) can target 60% or more, with inherently zero emissions and nearly silent operation.

Davemart

Or simply go the FCEV option which don't have the problem.

Paroway

Yes, buy a FCEV and no problem, because you can't go anywhere anyway without a network of fueling stations.

Lad

How about a cold weather portable (removable) factory heater kit consisting of a third battery charged by the car's system and a resistive heater all integrated properly in the car? How about a factory option: a larger battery and heater for the cold weather climates? Burning fossil fuel is my last choice.

HarveyD

EVs need 120 to 150 kWh to operate in very cold weather areas. Theo Taxis went bankrupt with a mixed fleet of 87 new EVs because too many hours were used to recharge the batteries 3 to 4 times a day.

A fleet of long range FCEVs would have a much better chance to survive.?

mahonj

@Harvey, definitely.
Question is: could you use EVs in summer and PHEVs in winter, or do you need PHEVs all year round ?

gryf

AAA has reminded all that EV require more battery energy in cold weather, something well known for the past decade when the first short range EV appeared.
This is great advertisement for Eberspaecher, Bosch, Borg Warner, and Mahle. These companies make Thermal Management systems for EV. The latest Audi e-tron also has a sophisticated thermal management system (https://www.e-tron.audi/en/highly-efficient-recuperation-aerodynamics-thermal-management-10676) nothing like a 2011 Nissan Leaf - which is not unlike early ICE autos which did not get good heaters until the 1930s.
If you want to go full high tech you could go with a Thermal Storage system (check out
"Design and Testing of a Thermal Storage System for Electric Vehicle Cabin Heating " DOI: https://doi.org/10.4271/2016-01-0248, https://www.sae.org/publications/technical-papers/content/2016-01-0248/preview/). Mahle was involved with this research.
Eberspaecher has been involved with vehicle heating systems since 1933 and still has a product line of fuel operated cabin heaters. They even produced a PTC (Positive Temperature Coefficient) heater for Nissan (ref: https://www.greencarcongress.com/2017/04/20170406-eberspaecher.html)
Also, GCC did a post in 2015 about "Bosch presenting a new heat-pump EV thermal management system at IAA . . .", ref:https://www.greencarcongress.com/2015/09/20150908-boschiaa.html.

HarveyD

Trouble with EVs in very cold (snowy) weather is not only a matter of keeping batteries warm but the electricity required to defrost windows and keep passengers in the temperature comfort zone and the extra energy to propel the vehicle through deep snow and frequent traffic jams etc.

If you live in a cold weather area, you are better off with an extended range quick refill FCEV or a PHEV with larger batteries or a BEV with 120 to 150 kWh battery pack.

Acceptable extended cold weather range PHEVs and BEVs are too heavy with current low performance batteries and use too much energy to move around.

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