A guide to charging EVs in hot weather
Drivers have long known the effect that extreme cold can have on battery performance. Long before electric vehicles (EVs) were commonplace, many a car struggled to start on a brisk winter morning. Yet, now that we’re asking batteries to do far more than provide a kick-start and power accessories, the question of temperature’s impact on their performance has become much more salient.
As it turns out, cold isn’t the only weather extreme to consider when it comes to EV battery performance. Heat can also reduce driving range and cause long-term battery damage. The good news is that there’s a lot you can do to mitigate the effects of those hot summer drives on your EV battery.
Optimizing your car for summer driving comes down to how you’re charging your EV in hot weather, along with a few other factors. Here’s a look at how hot weather affects your battery—and what you can do about it.
How hot weather affects your EV battery
The lithium-ion batteries that power electric vehicles have an ideal operating range, with the sweet spot right around 70 degrees Fahrenheit. That’s where the chemical reactions required for your battery to provide power happen most efficiently. Coincidentally, it’s also where you’re most comfortable—and less likely to use heat or air conditioning that draws more power from the battery.
Most EV drivers are already familiar with the effects of cold weather on their batteries. According to data collected by Geotab, a car running in 20 degree temperatures with the heater on loses around 40% of its battery capacity, on average.
On the other end of the temperature spectrum, the impact is less severe but still notable. At 100 degrees, a typical EV battery drops to about 80% of its rated capacity. This difference is largely due to the fact that we don’t see nearly as extreme temperatures above 70 degrees as we do below it.
Heating your car requires more battery power in an EV than in a gas-powered car, as you don’t have the ready heat source of a hot engine. This puts greater demand on the battery in winter than in summer. It’s worth noting that extreme weather has a similar effect on driving range for both EVs and gas-powered cars, so this is no reason to put off that EV purchase you’ve been considering.
Tips for efficient EV charging and driving in hot weather
Clearly, it’s in your best interest as an EV driver to do everything you can to diminish the impact of heat on your car’s battery. Fortunately, there’s a lot you can do. Here are seven ways to improve EV battery performance in hot weather.
1. Consider the thermal management system before you buy
Because temperature control is so critical to battery performance, every EV comes equipped with a thermal management system designed to keep the battery at optimal temperatures. These come in one of two forms: active or passive thermal management.
A passive system is simpler and relies on convection to cool the battery, whether by air or phase change materials. This is a less costly setup and may be sufficient in milder climates. However, if you live in a climate with seasonal temperature extremes, you should consider an active thermal management system. This circulates liquid coolant around the battery for a much more effective cooling solution.
Before you buy an EV, consider your typical driving conditions and find out what kind of thermal management system the car has.
2. Don’t park in the sun
Every car—electric or not—soaks up heat when you park it in direct sunlight. Those scalding temperatures mean you’re already starting with a hot battery—and you’ll have to run the air conditioning that much harder to cool down. Neither of those situations is good for battery range, so be sure to park in the shade whenever possible.
3. Don’t charge fully
Although it may be tempting to max out your charge every time, this practice won’t do your battery any favors. Lithium-ion batteries perform best when you keep their charge level under 80%. Frequently charging past this level will increase resistance within your battery and accelerate long-term degradation. Unless you need more energy for a longer trip, there’s no need to charge your battery all the way.
At home, we recommend using convenient smart charging to manage your charge level so you don’t even have to give it a second thought.
4. Charge overnight
When it comes to charging an EV in hot weather, charging at night is ideal. By charging overnight, you avoid the extreme heat and put less pressure on the electrical grid. If your utility company offers discounted rates for overnight electricity use, you benefit even further by saving money on your electrical bills.
If you live in a hot, muggy summer locale, you may find your car is already uncomfortable when you set out for work in the morning. If so, you can make your commute more efficient by preconditioning your vehicle before you leave.
Start your EV a few minutes before your commute and run the air while it’s still plugged in. That way, you’ll get your cabin to a comfortable level without draining any energy from the battery, and you won’t need to run the air as much while you drive.
6. Turn down the A/C
For less frequent EV charging in hot weather, few things matter more than how much you run the air conditioning. One study by AAA showed that battery range dropped 11% more with the air conditioning on at 95 degrees than it did without A/C. If you want to optimize your EV battery in summer, run the air conditioning less often—and keep it on low when you do.
7. Take it easy
Similar to a gas-powered car, your driving style also affects battery performance. Hard acceleration increases energy demand, and slamming on your brakes diminishes the effects of your vehicle’s regenerative braking system. Ease up on the lead foot, and your battery will thank you.
On a similar note, consider what you really need to carry in your vehicle for your summer commutes. The more weight you add, the more strain it puts on your battery, so keep it light to get a little more out of every charge.
Optimize your EV in summer
Temperature extremes will always affect EV battery performance, but just how much they do is up to you. By implementing some best practices for charging EVs in hot weather—and staying smart about your summer driving habits—you can significantly improve your battery health in the heat.
One of the best ways to optimize your battery life in the summertime is to charge at home overnight. If you haven’t yet installed a home charger, now is a great time to take advantage of federal and state tax incentives. Check out JuiceBox, our flagship home EV charger, for faster and cleaner EV charging day or night.