Can’t Take the Heat: How hot weather can affect EV range

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Most gearheads are aware that temperature extremes during winter months can scupper the total driving range of an electric vehicle. In fact, this quirk is often highlighted by proponents of gasoline-powered cars as to why EVs will never truly take off in certain parts of this country. And, to a degree, they may have a point.

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But according to the boffins at Automotive News, extreme heat can have similar effects.

Referencing a study completed by an analytics company in Seattle, ambient temperatures of over 100 degrees Fahrenheit (38 Celsius) can significantly sap range from an EV’s battery. The group has apparently tested thousands of machines in various climates, observing some of them shedding up to 31 per cent range when the mercury climbed over 100°F. Testing carried out in the less extreme temps of 90°F/32°C saw a range loss of roughly five per cent.

The reason, as always, is the current technology found in battery chemistry. A tech director from the University of Michigan explained to Automotive News that triple-digit temperatures can cause a breakdown of something called the “passive emission layer” on the battery anode, creating consumption of the unit’s liquid electrolyte. It is also well known that running ventilation systems in an EV (for either heating or cooling) can impact range as well since some of the battery’s juice is being diverted to cabin comfort instead of propulsion. The energy has gotta come from somewhere.

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This author just spent a week on a road trip in the American southwest, experiencing firsthand how baking in near 50-degree Celsius heat with single digit humidity can affect a gasoline-powered car. Economy was less than impressive, thanks to a constant running of air conditioning, to say nothing of the machine’s cooling fans which routinely sounded louder than a Huey over Huế, though range was certainly not cut by a third.

While the prodigious rate of gasoline consumption rankled, at least it was easy (and quick) to refuel and hit the road. That same statement cannot be said — yet — for electric cars, though that doesn’t seem to have put a damper on sales of Teslas and other EVs which your writer saw appear on streets in the flaming southwest like kudzu in a cornfield.

Here’s the good news: this research shows the scale of range depletion is more logarithmic than linear, meaning sane temperatures near the 30°C mark do not abuse batteries at headline-screaming levels. Progression with the development of solid-state batteries will also help, since it is generally accepted some solid electrolytes are less sensitive to wild temperature swings than liquid ones.

Still, it’s cause for thought, especially with meteorologists suggesting our planet sizzled to a global average heat record last month.