Navigating Severe Cold and Heat – Do Electric Vehicles Deliver Reliable Performance?

In This Article

• How Temperature Generally Affects Electric Car Batteries
• How Temperature Specifically Affects EV Range
• Heat Pumps vs. Resistive Heaters in EVs
• 9 Ways to Manage Range in Extreme Weather Conditions

Electric vehicles can work in any temperature although they do work best in a sort of Goldilocks temperature range where the outside environment isn’t too cold to have an adverse effect on the battery capacity and isn’t hot enough to require air conditioning.

Electric vehicle range in extreme cold and heat may not be as dire as you expect though and, for the record, gas-powered vehicles aren’t immune from temperature extremes either. Still, it’s advantageous to understand how heat and cold impact EVs.

How Temperature Generally Affects Electric Car Batteries

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Overall, EVs can and do perform well in all types of weather. Some weather conditions, just like with gasoline-powered vehicles, do mean that EV owners need to pay a little closer attention to the way they drive and conserve battery energy.

For example, EVs work better in extreme heat than cold because cold enough weather will temporarily reduce the capacity of EV batteries. Turning on the air conditioning in hot weather, however, can also reduce overall range.

All of this is because electric car batteries are significantly more advanced than most of the batteries we run into in our daily lives, but they are still bound by the same basic laws of physics. That means EV batteries work in slightly mysterious ways to most of us.

The key to understanding temperature impact on EV batteries lies in remembering that, first and foremost, the battery must be able to effectively hold and discharge energy. That means a battery must not only be able to powerfully charge the car, it must be able to hold enough charges to use when needed in different driving situations.

The ability to hold those charges is referred to as ‘capacity’ or ‘storage capacity’. When those charges are used by the car, they are ‘discharged’ by feeding power to the EV’s motor.

When a battery is exposed to extremely cold temperatures, its capacity to store a charge can be diminished. According to one study, lithium ion battery charge capacity drops to about 77 percent at a testing temperature of 5 degrees Fahrenheit , and measured discharge capacity drops to 82 percent at the same testing temperature.

EVs use lithium ion (Li-ion) batteries. These are rechargeable, lightweight, and have a higher energy density than other types of rechargeable batteries. As a result, these batteries are smaller than those in gasoline-powered vehicles.

Although battery capacity typically increases as the temperature of the battery increases, extremely high external temperatures can actually cause deterioration and even lower the operational life of a battery. That degradation can cause an EV battery to perform less effectively.

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How Temperature Specifically Affects EV Range

Temperature issues don’t just affect the battery itself. It can also impact an EV’s overall range.

Temperature affects EV range from both a capacity and use perspective:

1. Low external temperatures can reduce the storage capacity of EV batteries, which means the EV can’t store enough battery charges to go as far as it normally would.
2. The drain from heating or cooling the interior cabin of an EV can reduce the available amount of stored energy needed to actually move a vehicle from point A to point B.

The effect of low or high external temperatures on battery storage capacity is an important factor, but it doesn’t fully account for the reduction in EV range seen in both low and high temperatures.

It turns out that driver and passenger comfort actually has a bigger effect on EV range because it takes a lot of power to heat or cool the cabin of an EV in extreme weather conditions. In fact, real-world testing has shown that EV range drops to about 54 percent when the ambient temperature dips to 5 degrees Fahrenheit. That reduction is usually due to the power requirements of running an electric heater in extremely cold conditions.

This is one area where gasoline-powered vehicles have an advantage, because internal combustion engines generate a lot of waste heat as a natural byproduct of operation. That makes it essentially free to heat a gas-powered car, while an EV instead needs to send energy that could have otherwise gone to increasing its range into running a heat pump or resistive heater.

However, gasoline-powered vehicles still experience troubles in extreme weather situations, too, including reduced fuel economy in cold temperatures due to other factors. According to the U.S. Department of Energy, gas-powered vehicle fuel economy drops by about 15 percent when the temperature dips to 20 degrees Fahrenheit compared to fuel economy in balmier conditions.


PHOTO:

Bailey Mariner

When extreme temperatures swing in the other direction, EV range reduction is entirely due to the energy costs of cooling the cabin. This is an area where gas-powered vehicles don’t have an advantage, because running the A/C in a gas-powered vehicle takes gas that could have otherwise been used to move the vehicle.

According to the U.S. Department of Energy, a gas-powered car can have its range decreased by over 25 percent when running the A/C in extremely hot weather. In comparison, the average EV can be expected to reach about 80 percent of its rated range in conditions where the ambient temperature is 104 degrees. In that particular situation, an EV is likely to beat a gas-powered vehicle in terms of retaining more of its range.

Heat Pumps vs. Resistive Heaters in EVs

Both resistive heaters and heat pumps can be used in EVs. The benefit of using a heat pump in an EV instead of a resistive heater is that heat pumps are simply more energy efficient.

Resistive heaters convert electrical energy into heat because they get hot when electricity flows through them. Heat pumps, on the other hand, essentially just move thermal energy from one place to another.

An air conditioner is kind of like a one-way heat pump that moves heat from the interior of a vehicle to the exterior, effectively cooling the interior in the process. Heat pumps are reversible, too, which means that one can be used to either raise or lower the temperature in an enclosed space.

In fact, according to one study available from the NHTSA, the range of an EV with a heat pump is about 30 percent greater than the range of an EV equipped only with a resistive heater when operated in extremely cold temperatures.

Heat pumps are typically capable of operating in EVs in temperatures down to about 25 to 30 degrees Fahrenheit, although efficiency does drop off the colder it gets. In even colder temperatures, it becomes more efficient to switch over to a resistive heater.

9 Ways to Manage Range in Extreme Weather Conditions

While it’s true that EV range can be reduced by both extremely hot and cold weather, there are a number of things you can do to improve the range of an EV in extreme weather conditions:

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1. Reduce the use of air conditioning in hot weather. Set the A/C at the highest temperature you’re comfortable with, and consider cooling off with other methods like a portable battery-powered fan and an ice chest full of cool drinks when going on long road trips.
2. Don’t use accessory systems unless you need them. All the systems in your EV draw power from the same batteries, so everything from using the entertainment system to turning on the headlights instead of just the running lights during the day can cut into your EV’s range. Keep nonessential use to a minimum to improve your range when you’re already needing to draw extra power to heat or cool the cabin.
3. Heat or cool your EV’s passenger compartment while it’s still plugged in. If you think ahead and get the cabin to a comfortable temperature ahead of time, you won’t need to burn through battery power once you’re on the road. If you can keep your EV in a garage, especially a climate-controlled garage, all the better.
4. Park in the shade when it’s hot out. You’ll still need to run the A/C during extremely hot conditions, but parking in the shade will keep the passenger compartment cooler and you won’t need to use as much energy to get comfortable.
5. Try to stick to economy mode if your vehicle has it. Most EVs have a mode like this that provides better battery life, and range, at the cost of performance.
6. Take it easy when starting and stopping. Sudden, hard acceleration takes a lot more power than accelerating slowly. On the flip side, your EV’s regenerative braking system captures a lot more power when you brake slowly, anticipating a stop early, than it does when you slam on the brakes at the last moment. Keep in mind that if you’re driving in extreme conditions, like ice or snow, that will also affect how long it takes you to stop.
7. Keep your cruising speed under control. Most EVs provide the best battery life, and longest range, when you keep your speed below 50 MPH. Efficiency, and range, drop off sharply after that.
8. Avoid charging your battery outside when the ambient temperature is extremely cold. Battery charging capacity drops off the colder it gets, so you start from a better place if your battery isn’t extremely cold during the charging process.
9. Keep your load light. Did you load up for a skiing trip or a day at the beach on the weekend? Driving around with all that extra weight all week will reduce your range. If you have a rooftop cargo carrier, consider removing it as well when it isn’t in use, as the extra drag will also reduce your range.

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