The budding trend toward battery-powered cars is unfolding as new mainstream models from General Motors, Nissan and others proliferate rapidly in the U.S. market, introducing an alternative mode of vehicle operation, which drivers accustomed to gas pedal and brake may find unfamiliar.
The accelerator of a pure electric vehicle, operated by the right foot as in a conventional vehicle, no longer qualifies as a "gas pedal"- strictly speaking – since an EV doesn't use gasoline as fuel. Instead, an EV's pedal controls the flow of electricity in two directions: to propel the car and to slow it down.Likewise, a conventional brake, operated by the left foot, that relies on friction for stopping is needed far less – and sometimes not at all – to slow the car. Instead, EVs rely in varying degrees on so-called regenerative braking. This type of braking converts the kinetic energy of a vehicle into electricity to slow the vehicle down; the electricity produced serves to recharge the battery.
But the strength of regenerative braking offered by manufacturers and the way regeneration is controlled are as varied as the different types of EVs.
Nissan's second-generation Leaf EV, debuting in the U.S. in early 2018, comes equipped with a driving mode the automaker calls "e-pedal," a surrogate for a gas pedal and one of the more powerful regenerative formats among EVs on the market. In e-pedal mode, the driver is able to drive the new Leaf most of the time with just the right foot, using the friction brake sparingly or when a sudden stop becomes necessary.
Depressing Leaf's e-pedal propels the car; as soon as pressure from the right foot is reduced, regenerative braking begins.
"We didn't offer e-pedal on the first generation Leaf because our first EV was conceived to feel more like a normal gasoline-powered car," said Owen Thunes, a manager of Nissan's powertrain technical affairs.
In Nissan's first generation Leaf, introduced at the end of 2010, lifting one's foot from the accelerator produces a relatively light regenerative braking effect, measuring about 0.03 g (g being the force of the earth's gravity). The force of the regenerative brake on the new Leaf is rated at 0.2 g or about seven times the previous model, Thunes said. In additional to the e-pedal, the new Leaf also offers two settings for a more conventional driving feel, with less regenerative braking effect.
BMW's i3 is another EV with a relatively strong regenerative braking format. The German automaker has been tinkering with EV drive formats since 2011, discovering in surveys and testing that consumers reported a "strong passion" in favor of one-pedal vehicle operation made possible by powerful regenerative braking. I guess the use of regenerative braking, by extending the range of the vehicle, may subtly reassure drivers that energy is being conserved.
I borrowed an i3 from BMW to test for about a week over a number of different urban and suburban terrains and through various traffic situations in southeast Michigan, including slow commutes and on the Interstate at higher speeds. As with most EVs, the i3 operated quietly and delivered better-than-average pickup. Equipped with a 33 kWh lithium-ion battery powering a 125-kilowatt motor, i3's range is rated at 114 miles under normal conditions – fine for around town, dicey on longer jaunts.
In the first minutes behind the wheel of the i3, I found myself intuitively judging distances to the vehicle ahead and to stoplights and then adjusting speed and braking by either depressing the accelerator or lifting my foot slightly. An icon on the instrument panel indicated when electricity was being used to drive the vehicle and when the reverse was true, when deceleration was taking place and electricity was charging the battery.
The i3's instrument panel also indicated how many miles of range remained, a function of how much charge was left in the battery. But that number changed depending on how I was driving. When accelerating quickly, the computer in charge of calculating range estimated a lower number based on its observation that my driving style would use a lot of juice. When I drove more slowly and evenly, the estimated range remaining went up. (Unless you coast the i3 from the top of a tall mountain to the bottom, it's unlikely the regenerative braking alone can be sufficient to recharge its battery completely.)
I've tested GM's Chevrolet Bolt EV on a couple of occasions, a model notable because it outsells all other EVs in the U.S. and captured more than half the market for such vehicles in October. In addition to the regenerative braking applied when the driver's foot is lifted from the accelerator, Bolt features a hand-operated paddle on the left side of the steering wheel. Depressing the paddle produces about .3 g of regenerative force, enough to bring vehicle to a complete stop without the foot brake.
Bolt's paddle feature worked well. The only bit of awkwardness occurred when searching for the paddle while turning the steering wheel, such as when a driver would want to slow the vehicle while going around a curve. Since the steering wheel isn't in the same position as when the car is traveling in a straight line, the position isn't immediately apparent, necessitating use of the foot brake instead.
I expect that control functions will get better and better as the newest EVs come to market, which will happen at a pretty quick pace over the next few years.