Tips to Keep Electric Car Batteries Healthy in the Heat

Reader Contribution by Plugincars
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Reposted with permission from PluginCars.

Temperatures in many U.S. states are reaching record-breaking highs this summer, making even the most normal of everyday activities unbearable for all but the most hardened heat-loving Americans.

Like humans, electric car battery packs prefer moderate temperatures rather than extreme ones. What can you do to keep EV batteries happy in unbearable weather?

Avoid Extremes of Use

Just like any other battery pack, passing current in and out of your car’s battery pack will warm it up. The higher the current passing through the battery pack — either in or out — the quicker the pack warms up.

It’s worth noting too that as the battery pack reaches 20 percent full or less, its cell voltages start to drop dramatically. Since electrical power equals voltage times current, the current drain on the battery pack will increase as the pack voltage drops to maintain the power levels demanded by the car. This will in turn heat your car’s battery pack up — not exactly what you want when it’s already in the triple digits outside.

To keep your electric car battery pack as healthy as possible and as cool as possible, it’s best to avoid heavy acceleration and running your vehicle down to a low state of charge.

Charge Smart

As we’ve just explained, passing high currents through your car’s battery pack will cause it to heat up far more quickly than passing low currents through it.

Because the CHAdeMO quick charge and Tesla Supercharger stations rely on extremely high current flows to quickly replenish the battery packs on cars like the Nissan LEAF or Tesla Model S to 80 percent full in less than 30 minutes, think twice before using them when the mercury is reaching for the sky.

The same is true for 100 percent or ‘range’ charges in hot weather. As a battery pack reaches a full state of charge and its internal resistance rises, it becomes harder and harder to push electrons into the battery. In turn, this puts additional stress on the battery pack and increases the rate at which it heats up.

Consequentially, if you know you only need an 80 percent charge to reach your destination, setting your car to stop charging at 80 percent will put less strain on it and help it stay healthy in hot weather.

Park Smart

With the sidewalks in some cities hot enough to give pedestrians second degree burns, you need to make sure that your car gets just as much shade as you do. Where possible, park in the shade out of direct sunlight, as this should help your car’s battery pack stay cooler than it otherwise would. In addition, you’ll find your car far more pleasant to return to.

Keep Your Car Plugged In

While some cars like the Nissan LEAF and Mitsubishi i rely on passive forced air cooling to keep them cool in hot weather, others — such as the Tesla Model S, Chevrolet Volt and BMW ActiveE — use sophisticated thermal management systems with liquid coolant.

By closely monitoring the pack temperature, these fully-automated systems work by pumping refrigerant around the battery pack to keep them operating at peak efficiency. If your car is not plugged in, they will use some battery power to keep the pack cool. If your car is plugged in, they will generally run from mains power.

If your car uses an active thermal management system, it’s a good idea to keep it plugged in whenever possible in hot weather, to maximize range and keep the battery pack as cool as you can.

Photo by Nissan