How hot or cold weather affects electric vehicle range

Electric vehicles (EVs) differ significantly from gasoline-powered vehicles in many ways, but one of the less obvious differences is how extreme temperatures affect their driving range.

All vehicles lose range in very hot or very cold weather — after all, it takes more gas to heat an icy car — but EVs are especially vulnerable due to battery chemistry and the engineering environment. That doesn't mean they can't drive in bad weather, just that EV owners should take some precautions and plan ahead to avoid unexpected drops in mileage. We looked at how much EVs are affected by outside temperature, why it happens, and what you can do about it.

Measuring EV range in extreme weather

To understand how extreme weather affects driving range, the American Automobile Association (AAA), in partnership with the Automobile Club of the Automotive Research Center of Southern California, tested five electric vehicles with a minimum EPA-estimated driving range of 100 miles (161 kilometers). Real-world driving conditions are simulated using a dynamometer that provides tightly controlled ambient temperature in an enclosed test cell. To determine the effect on driving range, scenarios in cold and hot weather conditions (with or without air conditioning) were compared to driving scenarios with an outdoor temperature of 23.9°C.

  result:

When air conditioning is not used, the estimated driving range of electric vehicles is moderately affected by hot and cold temperatures compared to tests conducted at 23.9°C. The use of air conditioning resulted in a significant reduction in mileage.

-12% mileage reduction at -6.7°C

-6.7°C with heater (thermal air conditioner) mileage reduction -41%

-4% reduction in driving range at 35°C

-17% reduction in mileage with air conditioning at 35°C

These results mean that, on average, an electric car can travel 83 miles (133.6 km) with the air conditioner on at 35°C for every 100 miles (161 km) driven at 23.9°C, with the heater running at -6.7°C. It can only travel 59 miles (95 kilometers) without it. For example, an electric vehicle with a range of 240 miles (386.2 kilometers) might be able to travel between Los Angeles and Palm Springs on a fully charged battery in mild weather, but not in a 35°C heatwave with the AC on. Its range will be reduced by about 40 miles (64.4 kilometers), and the driver will need to charge it at least once during the trip.

Gas-powered cars are also losing mileage

-6.7 ℃ cold start mileage reduction -11%

-6.7℃ hot start reduction -6%

35 ℃ with air conditioning to reduce -17%

Electric vehicles are not particularly unsuitable for extreme temperatures. Tests at Argonne National Laboratory found that gasoline vehicles also experience a loss of range, although the phenomenon is often referred to as "decreased fuel economy."

When the weather is very cold, an oil-fired engine must burn extra fuel to bring the engine up to operating temperature - this is known as a "cold start". Engine fluid is also less efficient when it is cooler. When it's really hot, they have to burn extra fuel to keep the air conditioner running. In fact, on a percentage basis, gasoline cars suffer nearly the same loss of mileage at 35°C as electric cars with the air conditioning on.

Why EV range drops in extreme weather

Reason 1: Batteries don't like extreme temperatures

Like any automotive component, high-capacity lithium-ion batteries in electric vehicles have an optimal operating temperature range. As the temperature decreases, the diffusion, conductivity and reaction rate within the battery cell decrease. This results in increased voltage disturbances and heat generation, consuming energy that would otherwise propel the vehicle. At very low temperatures, additional energy may be used to heat the battery to prevent damage.

Also, at high temperatures, a cooling system must be run to prevent the battery from overheating. This also uses extra energy, which reduces driving range. Aggressive driving results in more heat generation, which increases the cooling demands of the battery.

Reason 2: Air conditioners consume a lot of electricity

In AAA's tests, the 2 largest drops in EV mileage occurred when the air conditioner was on. Anyone who's ever paid utility bills on a hot summer or cold winter day knows that air conditioners and space heaters consume a lot of electricity.

Using heaters (thermal air conditioners) at sub-freezing temperatures produced the largest drop in mileage. Unlike gasoline-powered cars, where the engine generates heat that can be used as a byproduct of combustion to heat the cabin, electric cars must run a separate electric heater.

  what can you do

• Efficiency (and savings): Electric vehicles (EVs) feel the effects of the weather better because it takes longer to recharge the battery than to fill the tank, but they have the advantage of being more cost-effective because every kilometer Electricity is cheaper than gasoline. AAA's research found that driving an electric vehicle for 1,000 miles (1,609.3 kilometers) with air-conditioning at an outdoor temperature of 35°C increases its electricity bill by about $8 (51 yuan) compared with a temperature of 23.9°C. By comparison, a gasoline car with an average U.S. fuel consumption of 23.6mpg would cost an extra $21 (134 yuan) for gasoline (this is a calculation made at relatively low gasoline prices).

• Plan Ahead: Check the weather forecast before a long trip to see if you're traveling in hot or cold weather. If so, plan to use the charging stations more frequently and map out the charging stations you will be using and the distances between them.

• Warm up or cool down before unplugging: While still connected to the charger, take time to warm up or cool the interior of the vehicle. This allows the battery to save more power for driving.

• Turn the air conditioner down a bit: Using a heater or air conditioner in cold or muggy weather is unavoidable, but if you want to extend your driving range, use them in moderation. Just like a room thermostat, set the air conditioner to a comfortable temperature.