Regenerative Braking and How it Works

One of the current buzzwords in the automotive industry is “regenerative braking.” Typically, this term comes up whenever the discussion turns to hybrid gas-electric vehicles, which employ this kind of advanced braking method to slow the vehicle as well as to supply power to the battery pack. But regenerative braking isn’t limited to hybrids alone. Indeed, electric vehicles and soon some mainstream models will include this technology.

A tale of two brake systems

Step on the brake pedal and a whole lot of kinetic energy is used to stop a vehicle. With traditional brake systems, that energy simply disappears. That’s unfortunate because if lost energy was somehow captured and converted into electricity, it could potentially recharge a car’s battery and power at least some of the onboard equipment.

When the first hybrid gas-electric vehicles were under development, that’s exactly what the engineers had in mind — capture wasted energy. After all, with a big battery pack storing electricity, it would need something besides the gas engine to help replenish the battery, in this case an electric motor. Furthermore, with the engine no longer powering the motor alone, overall fuel usage would also drop.

So, what’s the difference between brake systems?

In your typical vehicle, the traditional braking system creates friction with the brake pads and calipers, which ultimately slows or stops a vehicle. Friction is also created as the wheels slow down on the road.

On the other hand, with regenerative braking, the system that drives the vehicle does some of the braking. If you simply let up on the accelerator, the car begins to slow down as the engine works in reverse. Apply the brake and it’ll come to a stop faster.

Regenerative braking: drilling down

Earlier, we touched on some of the components comprising a regenerative braking system. One of those components is the electric motor. In a hybrid system, the motor takes kinetic energy, which is heat, and converts it into electricity. That electricity is typically sent to the battery through an inverter where it’s stored for later use.

The stored electricity will eventually be used to help power the hybrid vehicle. This is where systems vary by manufacturer, but in most cases, the electric motor taps the battery system to propel the vehicle at low speeds. Once you hit a certain speed or if more power is detected, the gas engine kicks in and the electric motor shuts off. However, under hard acceleration — such as when entering a highway, the engine and motor may work together to move the car.

In electric vehicles, you’ll find two or more electric motors as there’s no gas engine present. One motor is placed on the axle driving the vehicle, while the other serves in the traditional capacity of collecting kinetic energy and converting it to electricity.

Beyond hybrids and electric vehicles

Conventional hybrid vehicles, whether they also utilize plug-in power or not, and full electric vehicles, are the two main options for regenerative braking. Research by manufacturers reveals that regenerative braking systems are as much as 70% efficient, according to Electrek (a recognized electric vehicle news source). This doesn’t mean your driving range increases by 70%. Instead, upwards of 70% of the kinetic energy that would have otherwise been lost can now be used.

So, what about using regenerative braking in cars that aren’t hybrids or electric vehicles? Wouldn’t that be an efficient way to utilize kinetic energy for other purposes, perhaps to power certain systems?

It sure would! GM tried it as far back as 2009 with the Saturn VUE, utilizing a system that captured energy and used it to supplement the engine’s power, but not for providing propulsion on its own. Although the overall fuel economy improved, this so-called “mild hybrid” system didn’t go far enough.

Today, a handful of new vehicles are utilizing mild hybrids, including certain versions of the 2019 Ram 1500 pickup truck. The Ram’s system is especially interesting as the automaker layers a 48-volt electrical system on top of the standard 12-volt system. Thus, in equipped models, the Ram’s system supplies a boost of power that includes kinetic energy when accelerating. The result is a truck that’s faster off the line, with increased payload and trailering capacities.

Mild hybrids also power components such as the starter generator that replaces the alternator. It might also send power to operate the lights, navigation and audio systems.

Arriving soon

Regenerative braking certainly does have its benefits, but there are some disadvantages too. For one, regenerative braking adds to the cost of a vehicle. For another, braking often feels awkward for drivers who sometimes complain about the “spongy” feel.

Fortunately, the two disadvantages become much smaller as manufacturers reduce costs through newer and more cost-efficient systems and improve braking feel with these same new systems. Finally, you’ll also save money on the car’s brake system as pads and rotors last longer.

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