How Does Regenerative Braking Work?

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When referring to cars, energy efficiency refers to the number of miles you can get per gallon of fuel. Essentially, it’s the bang for your buck, and it’s very important to consumers, which is why the automobile industry has spent decades trying to maximize it. This is one of the main reasons that hybrid vehicles, such as the Toyota Prius, have come into prominence in recent years. So named because they are able to switch between gasoline power and an electric battery in order to cut down on fuel costs, manufacturers have equipped hybrid cars with dozens of features in order to maximize their energy efficiency.

One of the most effective methods for improving the fuel economy of a hybrid car is known as regenerative braking. As its name suggests, it is a type of technology that can “regenerate” your vehicle’s battery when you step on the brakes. But how does regenerative braking work? Is it really as effective as its proponents claim? Are there any downsides to it? Read on to find out:

Energy Efficiency: What You Need to Know

This article is about energy efficiency, so we should perhaps clarify what we mean by energy. The dictionary definition states that energy is simply the capacity to perform work. However, this means different things depending on the type of work that is to be performed.

When it comes to a hybrid car, there are several types of energy we’ll refer to. There is the electrical energy generated by the battery. This must be converted to mechanical energy to cause the axle of a car to generate torque, which is the force that causes the wheels to turn. The more torque your engine can generate, the more powerful your car will be.

A vehicle that can generate more torque and move the vehicle comparatively further with less fuel is referred to as efficient. If your vehicle utilizes a combustion engine to generate the torque that’s needed to move the car, some of that energy will inevitably be lost along the way. This is a simple fact of the laws of physics: there is no way to prevent some energy loss from occurring. Manufacturing is always seeking ways to cut down on that energy loss, decreasing the need for expensive fuel.

What Happens When You Pump the Brakes?

When you press the gas pedal on a traditional combustion engine vehicle, it pulls a throttle wire that increases the amount of air that is allowed to enter the engine. This increases the power and, in turn, the torque of your vehicle, causing the wheels to turn faster. Hybrid and electric vehicles use a digital controller to increase torque, but the outcome is the same: the car speeds up.

When it’s time to stop the car, you take your foot off the gas and apply the brakes. Of course, a single foot isn’t enough to stop a vehicle that’s moving upwards of 60 miles per hour, so your vehicle offers some mechanical help. A pressurized hydraulic system causes a brake drum to clamp the brake pads down on the wheels of your car (this is the reason your car has brake fluid, which needs to be replaced every once in a while). The friction created by this process causes the car to slow down and, eventually, come to a stop.

Anytime you apply the brakes to stop the car, however, you are essentially creating a conflict between two forces: the engine torque, which is trying to move the car, and the friction of the brakes, which is trying to stop it from moving. This means that the engine is still working, despite the fact that the car is beginning to slow down. This results in wasted energy: the power your engine generates is now being lost completely as heat energy. This means that every time you apply the brakes, you are losing precious fuel.

Enter Regenerative Braking

Car manufacturers have long sought ways to cut down on wasted fuel, and one ingenious method they have introduced is regenerative braking. The core concept is that a great deal of energy is generated—and then wasted—whenever you use the brakes on your car. Manufacturers wondered if it would be possible to recapture some of that energy and essentially put it back into the car for later use.

To really answer the question of how does regenerative braking work, you need to have an idea of how an electric generator works. It does so by transforming mechanical energy back into electrical energy: the physical turning of a rotor around an electric coil uses the induction principle to create voltage.

Regenerative braking works in much the same way. Instead of relying on traditional friction-based brake pads, regenerative brakes simply put the engine into reverse. The energy that is then generated—by the friction from the road, among other areas—causes voltage to be generated. This is then converted to electricity, which is immediately stored in your hybrid car’s battery cells. In turn, this will extend the range of the battery and allow your vehicle to be a great deal more energy efficient. Studies have shown it to be very effective, recapturing 70 percent or more of the lost kinetic energy.

Pros and Cons of Regenerative Braking

There are plenty of pros to regenerative braking: primarily, of course, is its ability to cut down on your car’s fuel usage. This will not only save you money on gas, but it will also extend the range of your car. This is important during long drives: the longer your vehicle can run, the less likely it is to run out of fuel entirely and strand you somewhere.

When it comes to downsides, there are very few for regenerative braking. There is a slight learning curve, depending on the technology that’s being applied in your car (you may have to figure out how to switch your regenerative braking system on).

You will also need to find a mechanic who understands how this type of technology works and is able to maintain it. For this reason, we recommend having all of your regular maintenance performed by your original dealer, such as Beaverton Toyota, as they will specialize in your specific make and model of the car and its unique parts.

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