You’ve probably heard car reviewers talk about “one-pedal driving” when discussing electric vehicles. But what exactly does that mean? Certainly electrics still have two pedals, an accelerator and a brake. Although most of the time a one-pedal-capable EV is described as sporty and fun, there are some drawbacks.
- High levels of regenerative braking, enough to slow and stop the car quickly, make one-pedal driving possible.
- One-pedal EVs can be more engaging for enthusiasts, similar to cars with manual transmissions.
- More regenerative braking increases electric vehicle range.
- One-pedal operation must usually be selected by the driver, although systems differ.
- Aggressive regenerative braking can be upsetting to passengers.
- One-pedal operation may not work when the temperature is very cold or the battery is full.
Where Did One Pedal Driving Come From
Not long ago, cars had three pedals, with an accelerator, brake and clutch. Manual transmissions demanded that extra pedal. The vast majority of today’s cars shift themselves, reducing the pedal count to two. Normally, both pedals are operated with the same foot, your right.
In some electric vehicles, however, there’s little need to use the brake. The regenerative braking system activates immediately after lifting off the throttle, bringing the vehicle to a quick stop all on its own. This is what’s referred to as one-pedal driving. As with so many aspects of electric vehicles, we have Tesla to thank for this new paradigm. Its original Roadster pioneered the concept of one-pedal driving.
How Does Regenerative Braking Work
Other early electrified vehicles, notably hybrids such as the Toyota Prius, blended the force of regenerative braking with the actual friction brakes. This made the driving experience similar to that of a conventional vehicle. It was thought that customers would reject EVs if they didn’t mimic the behavior of familiar vehicles with internal combustion engines. Take your foot off the accelerator in a conventional car and it coasts, with only mild engine braking slowly bringing it to a stop.
The Tesla Roadster, however, drove radically differently. The acceleration provided by its electric motor was breathtaking, but what really interested sports car enthusiasts was the way it decelerated immediately after letting off the accelerator pedal.
This is because in an electric vehicle, the drive motor or motors are directly coupled to the wheels. As soon as the wheels are not being driven, they begin driving the motor, turning it into a generator. That force of momentum from the wheels regenerates electricity, charging the battery, and is referred as “regenerative braking.”
Is One Pedal Driving Easier
Tesla engineers tuned the Roadster to recoup as much energy as possible during deceleration, in part to extend its range to the utmost maximum. The byproduct of this strategy was that the car decelerated automatically, almost as rapidly as it accelerated. It made for a very fun car to drive!
But this can also create a nausea-inducing ride for passengers, if the driver isn’t practiced at controlling the braking force with the accelerator pedal. Drivers need to be careful in their application of the accelerator, or else the jerky, back-and-forth acceleration and deceleration creates a potentially unpleasant sensation. It takes some getting used to in order to drive a one-pedal electric vehicle smoothly. An experienced drive meters out the braking force by still pushing on the throttle pedal. It’s essentially the opposite of the brake pedal, with the less you’re pushing on the throttle, the harder the car is braking. Once drivers get the hang of it, however, they can even time their stops so that no braking with the brake pedal is required.
Current Tesla products have two levels of brake regeneration. The standard setting provides high levels of regeneration and a low setting permits more coasting during regeneration that makes it easier to drive the car smoother. Other EVs have an adjustable regeneration level, notably Hyundai’s Ionic and Kona electrics, so drivers can decide when they want the one-pedal experience.
Why Won’t My Regenerative Braking Work
Regenerative braking isn’t the same as friction braking. EV’s still have friction brakes, which convert kinetic energy of the car’s momentum into heat in the brake rotors. Regenerative braking converts this same kinetic energy into chemical energy in the batteries. But the batteries need to be able to accept the energy, or regenerative braking doesn’t work.
This means that there are two obvious situations where regenerative braking is compromised. The first is if the battery is already full. Fortunately, electric vehicles are programmed to leave a buffer such that a “full” battery can still take some charge. The second is if the battery is cold, which makes it more resistant to charge and risks damaging the battery if too much current is applied too rapidly.
For this reason, Tesla limits regenerative braking until a battery is at operating temperature. This causes the car to drive slightly different, but only on extremely cold mornings and only if the car has been parked unplugged.
One For You
Even those drivers who aren’t interested in sportiness may find one-pedal driving desirable. The feeling of being in control increases while in one-pedal mode, as the vehicle is immediately responsive to your right foot. Used regularly, it can extend the life of brake pads almost indefinitely. That alone should make the prospect of a one-pedal EV attractive.