Recovering kinetic energy during deceleration to extend driving range and improve efficiency
Explore the TechnologyKinetic Energy - As indicated, in conventional internal combustion engine vehicles, the kinetic energy of the vehicle is dissipated as heat during braking. However, the situation is completely different in electric vehicles. By controlling the electric motor to operate as a generator, the kinetic and potential energy of the vehicle during deceleration can be converted into electrical energy and stored back in the battery7 . This innovative technology is regenerative braking. For many interested in homemade electric vehicles, improving the efficiency of regenerative braking systems goes beyond mere technical curiosity to become a practical challenge of increasing driving range and minimizing energy consumption.
The core principle of regenerative braking is based on electromagnetic induction. When an electric vehicle accelerates or maintains constant speed, the electric motor converts electrical energy into mechanical energy to drive the wheels. However, when braking is required, this process reverses. When the driver presses the brake, the control system switches the motor to generator mode. This causes the vehicle's kinetic energy to rotate the motor/generator, generating electrical energy5 7 .
The generated electrical energy is transmitted to the battery through a power conversion device for storage6 . In this process, the regenerative braking system also produces a braking effect that slows down the vehicle. This allows energy that would have been wasted when using only conventional friction braking to be recycled into useful electrical energy.
The efficiency of a regenerative braking system is determined by several factors. The main factors are as follows2 7 :
Kinetic energy propels the vehicle forward
Driver presses brake pedal
Motor becomes generator, creating electricity
Electricity stored in battery for later use
The core of a regenerative braking system lies in the algorithm that determines optimal braking force distribution. According to research, differences were observed in the regenerative braking amount and final battery SOC value between algorithms applying an ideal braking force distribution curve and those applying proportional distribution7 .
Modern regenerative braking systems monitor various vehicle state information such as battery SOC, vehicle speed, and motor speed in real time and dynamically determine the regenerative braking amount and hydraulic braking amount according to these conditions2 .
To enhance the performance of regenerative braking systems, perfect harmony with mechanical brakes is essential. For this purpose, regenerative braking electronically controlled hydraulic modules have been developed.
These modules consist of proportional pressure reducing valves, accumulators, power packs, stroke simulators, etc., and seamlessly combine traditional hydraulic braking with regenerative braking2 .
Recently, electric booster (eBooster) systems have gained attention. This system integrally performs braking force assistance and regenerative braking linkage, and uses BLDC servo motors and linear actuators to replace conventional vacuum boosters4 .
This makes the transition between regenerative braking and friction braking smoother, consequently increasing the amount of energy that can be regenerated.
A domestic research team conducted a systematic study to quantitatively analyze the impact of regenerative braking on battery SOC7 . The purpose of this study was to establish the relationship between the regenerative braking amount and the final battery SOC value, and to compare how different braking algorithms affect regenerative efficiency.
The experimental results confirmed that for both braking algorithms, the mathematical model could predict the simulation results with low error7 . This means that the relationship between regenerative braking and battery SOC is quantitatively predictable and can contribute to the development of more efficient braking algorithms.
| Braking Algorithm Type | Regenerative Braking Amount | Final Battery SOC | Prediction Error Rate |
|---|---|---|---|
| Ideal Braking Force Distribution | High | High | Low |
| Proportional Distribution Algorithm | Relatively Low | Relatively Low | Low |
| Battery SOC State | Regenerative Braking Efficiency | Main Cause |
|---|---|---|
| Low (0-30%) | High | High energy acceptance capacity |
| Medium (31-70%) | Medium | Gradual decrease in energy acceptance capacity |
| High (71-100%) | Low | Low energy acceptance capacity |
| Speed Range | Regenerative Braking Efficiency | Main Cause |
|---|---|---|
| Low Speed (0-30km/h) | Low | Small amount of kinetic energy |
| Medium Speed (31-60km/h) | Medium | Moderate amount of kinetic energy |
| High Speed (61km/h+) | High | Large amount of kinetic energy |
For those who want to research regenerative braking system efficiency or apply it to homemade electric vehicles, we've compiled the essential elements.
Motors, Power Electronics, BMS
Control Algorithms, Simulation Tools
AI, Machine Learning, Predictive Control
Storage, Conversion, Management
Regenerative braking technology has established itself as an important technology for improving the energy efficiency of electric vehicles. Beyond simply increasing driving range, this technology aims for greater values of energy self-sufficiency and environmental protection. For those interested in homemade electric vehicles, improving the efficiency of regenerative braking systems is a journey that offers both the practical value of reducing energy consumption and the sense of technical achievement.
Regenerative braking technology still has immense development potential. With the development of more sophisticated algorithms, more efficient power conversion devices, and more accurate battery state estimation technologies, much more energy can be recovered than currently possible. This will ultimately contribute to creating truly sustainable transportation that minimizes energy consumption.
Regenerative braking is a key technology in the transition to sustainable transportation, recovering energy that would otherwise be wasted and making electric vehicles more efficient and environmentally friendly.