Braking Story: A Single Pedal To Drive Your Car

Riding a bicycle is a very good form of exercise. You pedal, you brake, you pedal again. The calories burnt to provide the energy required to move the bicycle is what keeps you fit. But did you know that the energy that moves the bicycle is lost when you apply the brakes?

You see, in conventional brakes, most of the energy of the moving vehicle is lost in the form of heat. What if we could conserve this energy? Or at least recover a part of it and maybe use it to power the vehicle yet again. Well that is what is being done now, using a system called ¡®regenerative braking¡¯. Used in electric and hybrid cars, regenerative braking is able to conserve some of the energy released during braking and transfers it back to the car¡¯s battery, thus increasing the range of the vehicle. Efficient, right?

Now Honda is taking it a step further. It is making it sort of a mandate in its upcoming (and first ever) electric car - Honda E. A concept car for an urban commute at first, Honda E has finally taken shape into a production car, a car that will come with a single pedal system.

Honda E (Image: Honda)

Single pedal system - How does it work?

As can be guessed from its name, a single pedal system bestows most of the operations associated with driving a car on a single pedal - the accelerator. To be clear, such electric cars will have a dedicated brake, only that it won¡¯t be used much because the regular braking will be performed just by lifting your foot from the accelerator.

The working is quite simple actually. You press on the pedal to accelerate and when you have to brake, you simply lift your foot off it. In essence, a single pedal system uses regenerative braking to work. So as soon as you lift off your foot from the pedal, the regenerative braking kicks into action, thus slowing down the car for you.

To understand the workings of regenerative braking, let us recall the concepts of an electric motor and a generator. An electric car is powered by an induction motor, which rotates to move the car forward, i.e. it converts electrical energy into mechanical one. Interestingly, the same motor can also act as a generator, producing electricity from mechanical energy.

At the time of braking, the electric supply to the motor is cut and instead, the mechanical energy of the car powers the motor (now acting as a generator) to produce electricity, which is then fed back to the battery and thus helps in extending the range of the car.

Regenerative braking conserves energy for the battery, while in frictional braking, all the energy is lost in the form of heat. (Image: Bosch Mobility Solutions)

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Better than the conventional system?

The primary benefit of the single pedal system is the regenerative braking system it employs. While it does recharge the battery every time you brake, keep in mind that it also starts braking on its own every time you take your foot off the pedal.

Now take an example of a car moving at 60 kmph. In a conventional vehicle, leaving the pedal would mean that the vehicle will coast close to the speed until the friction and air drag eventually bring it to a halt. So even if you want to cruise at a steady speed, you can lift your foot off the pedal intermittently.

In a vehicle like the Honde E though, where lifting your foot from the pedal would initiate the regenerative braking, the car will come to a halt much faster than the previous instance. There is no doubt that some energy will be conserved through the braking and added back to the battery. But you will also need the same (practically more) energy to get the car moving at the same speed again i.e. if the speed drops to 40 kmph within 10 seconds of lifting your foot, you will have to accelerate yet again to reach back at the 60 kmph mark.

Now the question here is whether the energy conserved during the drop from 60 to 40 kmph is greater than that required to accelerate the car back to 60 kmph. It will not be, as even the best of the regenerative braking systems are able to conserve not more than 60% of the energy released during braking, as some of it is bound to be a part of aerodynamic and friction losses.

How a single pedal system works

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It should, however, be noted here that several Tesla owners (as Tesla cars also employ a single pedal system for regenerative braking) have mentioned that Tesla cars can coast easily. In fact, so much so that there have been no complaints about coasting at a speed from any of the Tesla users to date. For that, the amount of pressure applied to the pedal will have to be constant. Meaning, the neutral position for the pedal becomes the angle at which it already is at a particular speed. Any further pressure would accelerate the car, spending the battery¡¯s energy. Releasing the pressure will initiate regenerative braking, gaining energy for the car.

More importantly, regenerative braking is not effective as conventional braking through friction. This is exactly why any electric car with regenerative braking also comes with conventional brake modules.

For those who are still uncomfortable with the idea, know that all the cars employing the regenerative braking system offer the option of setting the regen braking as per the user¡¯s needs. Meaning, you can set the regen braking to the point of 0 kmph, or to a specific speed like 10 kmph, after which you will have to brake manually. You can even stop it altogether, controlling the braking of your car entirely on your own.

The regenerative braking constitutes all the braking torque at high speeds. As the car comes to a halt, the friction brakes take over with transfer of torque, a process called

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A unique concept?

Not really. While the single pedal system and regenerative braking might sound like futuristic solutions, they have been in use for a while now. BMW pursued the concept with its first EV pilot program back in 2008, using it in Mini E, Active E and then the production models of i3.

Even Chevrolet introduced it in its Bolt EV in 2016, with an option to toggle the amount of braking applied by the regenerative system through pedal shifts behind the steering. Nissan boasted of an extension of this system with its latest iteration of the ¡®Leaf¡¯, wherein the hydraulic brakes of the car kicked into action as soon as the foot is taken off the pedal.

All models of Tesla also come with such a system. Tesla owners can also control the amount of braking applied through the regenerative system through a simple dabble on the infotainment.

With the Honda E using the single pedal system, the relatively untouched mode of driving is set to gain momentum. The anticipation for the electric car is high and with its dedicated make for a city commute, such a system will attract a lot of attention from a lot of drivers who might have been sick with controlling multiple pedals in traffic by now.