When it comes to our cars, there is often a great deal we do not quite understand. How does the radiator keep the engine cool? We may not know this, but we do know to keep our coolant levels sufficiently full so it keeps doing whatever it does however it does it. Nowadays with electric cars and a changing transportation environment, there is even more to learn. No Fill Up has stayed on top of current advancements in electric car efficiency: there are emerging technologies that are changing the way our cars slow down and rebuild energy. Regenerative braking is one such technology.

regenerative braking

  What Is Regenerative Braking?

Regenerative braking is a modern technological innovation in the braking systems of electric trains and cars that incorporates regenerative brakes, or "regen" brakes, into the overall regenerative braking system.

Within traditional braking systems as we'll discuss, the energy generated from stopping a car is lost; however, in regenerative braking this energy is instead harvested and applied to acceleration.

The underlying purpose of regenerative braking is to effectively harness the energy of stopping our vehicles and apply it to an energy bank that can be drawn upon for acceleration.

To provide a basic understanding of the regenerative braking system, we'll explore the major steps. In an electric vehicle that is driven by a battery, energy flows through the battery into the wheels to propel your vehicle.

When the vehicle is braked, the energy that is generated through the braking is converted back into the batteries via the motor, which works as a generator of electricity.

Upon engaging the power again, the kinetic energy that was stored in braking is then available to be used for acceleration, creating a cycle of energy. We'll explore the process more in-depth in the following section.

  How It Works

Electric vehicles are powered through electric motors that are connected to the batteries. The batteries are typically charged through electric sources, but regenerative braking has presented a new means through which we can power our electric cars.

To propel electric vehicles, energy from the motor is transferred into the wheels to provide the essential kinetic energy to keep the car moving forward. When braking, the electronic circuits in the vehicle cut the power to the motors, then as the wheels brake they turn the motors.

When braking as the power is cut to the motors, the momentum and kinetic energy of the vehicle transfer through the wheels and back into the engine, producing kinetic energy.

This feedback cycle is made possible through the interplay between the electric motor and the circuits that govern the output or input of kinetic energy. Power from the motor generators flows back into the batteries, providing them with charge.

Through regenerative braking a percentage of the energy that would be lost by braking is instead returned to the batteries, making the system self-feeding through braking.

Electric Cars and Trains

Regenerative braking is used in different ways in different forms of transportation. Within the context of electric and hybrid cars, regenerative braking is used to charge the main battery pack.

Through the charging of the battery pack during use, the amount of time that the car can have between charges on the battery is increased.

This is a useful means of employing energy, and also reducing the necessity of remembering to plug the car in every night, or finding a location to park with a charging station, which depending upon the area you are in can be quite simple or a treasure hunt.

Electric trains that function through the use of overhead power lines function differently in their use of regenerative braking than electric cars.

Rather than sending energy back into batteries, electric trains instead return the energy produced through the regenerative braking system back into the power line itself to be used by all trains on the grid.

A typical electric train in the modern world is able to save about 15 to 20 percent of its energy through the use of regenerative braking systems. This novel means of harvesting energy from the regenerative braking system can save cities a significant amount in energy expenses.

Electric Bicycles

Regenerative braking technology is useful in bicycles as well, although applied in a slightly different way, and far less useful.

The primary means of energy production in regenerative braking in trains and cars is from the kinetic energy that build up from stopping an object with a large mass quickly when it has built up momentum.

Bicycles are not particularly bulky or heavy, and thus the benefits to of regenerative braking are minimal.

Further, the power is generated through an electric motor that is constantly engaged unlike most electric bicycles, so regenerative braking on bicycles amounts to a marketing feature more than a valuable source of converted energy.


One commonly used application of regenerative braking that seems entirely obvious now given what we're exploring but may previously have been surprising is elevators.

Elevators are heavy and bulky objects filled with people or inventory, also potentially quite heavy. As elevators come to a halt, they must apply brakes to cease the kinetic energy and momentum that they had achieved to begin moving.

Through regenerative braking in elevators, leading manufacturers claim that up to 75 percent of the energy normally used can be saved. Regenerative braking elevators can yield substantial returns for their investment.

Regenerative Efficiency 

The feedback cycle that is used with regenerative braking allows for power from the brakes to be fed back into the electric motor then into the batteries to achieve charge.

Is the feedback sufficient to completely power your car simply through ongoing braking and forward momentum? The simple answer is: no. Regenerative braking is a more gradual cycle than traditional braking, and so it takes greater time for the electric vehicle to stop, were it to rely upon regenerative braking alone.

This is not the case, since there are instances in which immediate braking is essential.

Given the importance of being able to brake and stop quickly in the event of a sudden change in operation, electric cars employ a combination of traditional friction brakes as well.

The friction brakes work in concert with the regenerative braking system, working more when sudden stopping is necessary and less when gradual braking is used.

Due to the contribution in braking of the traditional friction brakes, it is not possible for 100% of the energy produced from braking to be reclaimed by the regenerative braking system.

Regenerative Brakes vs. Traditional Braking System

Regenerative braking is of use in systems that are driven by electric motors. The ongoing engagement of the electric motor and the subsequent slowing thereof through a cycle of energy is essential to acquire the energy necessary out of braking to be regenerative.

Traditional vehicles however are driven by gasoline motors, and the braking of an automobile unfortunately does not randomly generate gasoline that we can then use to get more miles out of our car between fill-ups.

The source of power for the engine is the most essential difference between regenerative braking and traditional braking systems.

Traditional braking systems employ purely physical braking systems to bring our vehicles to a halt. There are brake pads or calipers mounted on the vehicle that clamp down in some manner or another upon the wheel, bringing the wheels to a halt and with them the vehicle.

Whether disc, caliper, or some other form of traditional braking system, what matters is that the brake pedal is depressed, and the pads clamp down upon the metal of the inner wheel, stopping the car through sheer physical force and momentum.

This places a great deal of stress on the suspension system, and as we'll see, wastes a great deal of energy.

The most significant difference between regenerative braking in contrast to a traditional braking system is energy efficiency.

When a car is stopped, a great deal of energy is effectively lost within a traditional braking system, as there is no means of absorbing the energy and translating it into power that could be used at a later time as with electric-engine driven vehicles. The energy is expended as heat.

This lack of energy efficiency however within-gasoline powered vehicles is inevitable, insofar as technologies have not adapted electric power into the system of traditional gasoline and diesel driven machines.


Regenerative braking is an intelligent means of harnessing energy that would otherwise be wasted and lost entirely. For electric cars, trains, and elevators, regenerative braking can save a vast amount of energy and resources.

Not having to charge your electric car as often will reduce your electric bill, in the same way that buildings using electric elevators with regenerative braking can save up to 75% of their energy costs from elevator operation.

Such investments are worthwhile and environmentally friendly.

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