Andrew Moseman has covered science, technology, and transportation for publications such as The Atlantic, Inverse, Insider, Outside, and MIT Technology Review. He was previously digital director of Popular Mechanics and now serves as online communications editor at Caltech. He is based in Los Angeles. Read MoreRead More
Why It’s Hard to Build EVs for Range Instead of Power
If you want an EV with great range, just drive slowly.
The last gas car I owned was underpowered. Equipped with a four-speed stick shift and an undeserved spoiler, the 1994 Ford Escort eked out all of 100 horsepower. It got you there, but it huffed a little on the way.
My current vehicle has no such struggles. The Tesla Model 3 accelerates happily thanks to its 269 horsepower, a figure that lives toward the lower end of modern EVs. It zips away from a red light thanks to the physics of a battery-powered car.
“The nice thing about electric vehicles is, they can provide full torque at zero speed, which internal combustion vehicles can't do. And that's one of the reasons why they have those improvements in terms of acceleration,” says Heath Hofmann, a professor of electrical engineering at the University of Michigan who has consulted with companies including Tesla.
The tale of my two cars is the story of the last half-century of auto engineering. Carmakers got good at delivering more power, so much so that someone behind the wheel of a family car today has as much horsepower at their feet as some sports cars of the late ‘80s and early 90s. Americans came to expect it. And now, in the burgeoning EV space, automakers chase Tesla’s success in selling electric vehicles on muscle and sex appeal by cranking out a new slate of EVs with lightning-fast zero-to-sixty times.
The green machines meant to reduce our transportation carbon emissions have become speed demons. But the specter of Americans driving mostly amped-up, super-heavy electric vehicles that are more dangerous to everyone around them has led many experts — including the chief of the National Transportation Safety Board — to fret about the direction of the EV revolution. It’s enough to make you wonder whether the swole EV could, or should, be tamed.
All that quickness comes in handy during a highway merge, sure. But like a lot of current combustion cars, the new electric vehicles are overpowered for daily driving situations, capable of acceleration bursts and top speeds that are impractical or illegal on public roads. At the same time, they also have a range problem. Extending how far they travel per charge would enhance driving quality of life, allowing people to drive further, and use their energy for ancillary applications, with less anxiety about running out.
Could the car companies churn out EVs that are optimized to go far instead of fast? Well, they could. Hofmann explains that an EV’s power depends not only on how much energy it can draw from the battery at a given time, but also on its drivetrain components, especially its electric motors. The most straightforward way to rein in an electric vehicle — to emphasize range and battery life at the expense of acceleration — would be to give it smaller motors that simply wouldn't allow for inefficient, aggressive driving. It’s (roughly) analogous to putting a smaller engine in a combustion car as opposed to a snarling, gas-guzzling block.
There are a couple of problems with that, though, starting with the car market. Last week, GM CEO Mary Barra said that electric cars under $40,000 still aren’t profitable, which is why there are so few. Vehicles that command prices above that mark are typically big, powerful machines, not economy cars whose zoom-zoom has been curtailed. Americans won’t pony up for wimpy cars.
Hofmann says there’s also an engineering quirk to consider. It turns out, he tells me, that larger electric motors tend to be more efficient than smaller ones. As a result, you might actually save a little energy by having big motors in your car, but using them conservatively, than by installing small motors that constrain your lead-footedness.
This leads us back to a familiar axiom: It’s not the car, but the driver. Much of the old wisdom about efficient driving is as true for EVs as it was for gas-burners: Driving slower saves energy, as does properly inflated tires, maintaining a constant speed instead of frequently stopping and starting, and turning down energy-sucking applications like climate control. Many new EVs reveal this truth in real time: They calculate exactly how many miles of battery life you cost yourself by driving 10 mph over the speed limit or running the air conditioning at full blast.
Speed is the big one, Hofmann says. Given that larger motors can be more efficient than small ones, the best thing to do for promoting EV range and efficiency may be to give drivers the power and hope they use it cautiously. The top-down way to make EVs go farther and drive safer would be for governments to change speed limit laws or mandate vehicles be electronically prevented from exceeding certain speeds, which unearths draconian memories of the “I Can’t Drive 55” 1970s and 80s.
It works. When I’ve driven my own EV on slower state highways — and stuck to the speed limit — I’ve been taken aback by how much I stretch the battery. That doesn’t mean a nation of speed limit flouters would happily comply.
“Really, if you wanted to force the cars to be efficient, you would limit them to go no faster than 55 miles an hour, right? Not too many people are gonna be okay with that,” Hofmann says.