Regenerative Braking in Hybrid and Electric Cars: How Do They Work?

Have you ever wondered whether regenerative braking in hybrid cars and electric cars operates in the same way? While the principle is largely the same, there are important differences in the setup and how the system functions. This article will explore the similarities and differences, highlighting the nuances of regenerative braking in both hybrid and electric vehicles (EVs).

How Regenerative Braking Works in Both

At its core, regenerative braking is a process that converts kinetic energy from the motion of the car into electrical energy that charges the vehicle's battery. This energy conversion happens when the electric motor-generator (MG) acts as a generator, slowing down the car by opposing the motion of the wheels.

In both hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs), the electric motor-generator is connected to the wheels. When the battery is part of the circuit, the motor-generator produces electricity that is stored back into the battery, thus regenerating the energy.

Powerful Regenerative Braking in High-Performance Vehicles

The performance of regenerative braking in many HEVs and BEVs can vary significantly depending on the vehicle's design. In high-performance models like the Tesla Model 3 and Model Y, regenerative braking is so effective that the friction brakes are barely used. On my Model 3 and Model Y, which are both dual-motor performance models, I rarely use the friction brakes; the brake disks are almost completely undamaged after 5000 miles.

Compare this to my previous Lexus RX450H, which featured motor/generators on both the front and rear wheels but had relatively weak regenerative braking. The weak regeneration was primarily due to the use of a CVT (continuously variable transmission), which was tuned to behave like a traditional car when braking.

Setup and Functionality

The system setup significantly affects the functionality of regenerative braking in HEVs and BEVs. In many hybrids, regenerative braking starts immediately when you lift your foot off the accelerator, whereas in most EVs, it begins as soon as you apply the brakes. This difference is due to the design of the vehicle’s electronic control systems.

EVs, with their powerful electric motors, can produce a much higher regenerative braking effect. The big difference is that in certain hybrid setups, there is a secondary mode where the motor/generator can use the engine as a brake, a feature not available in BEVs due to their smaller battery size and constant connectivity to the motor-generator system.

Driver Control and Coasting

There are some nuanced differences in how drivers engage regenerative braking in hybrids versus BEVs. HEVs often feature an advanced computer-controlled system that seamlessly balances the use of regenerative braking and friction braking, providing a smooth "brake feel" to the driver. In contrast, BEVs are designed to use regenerative braking primarily by releasing the accelerator pedal, with friction braking controlled by the brake pedal.

This difference in control can lead to a feature in BEVs known as "one-pedal driving," where the driver can control the vehicle's deceleration entirely through the accelerator pedal, eliminating the need to use the brake pedal at all.

Conclusion

While the fundamental principle of regenerative braking is the same in both hybrid and electric vehicles, the differences in setup and functionality can significantly impact the way it works in each type of vehicle. Understanding these differences can help drivers optimize their use of regenerative braking and enhance the overall driving experience.