How to Choose the Suitable Vacuum Braking System for the Electrification Conversion of Wuling Rongguang Mini Bus?
When converting the Wuling Rongguang mini bus from internal combustion engine (ICE) to electric powertrain, one of the most critical safety systems to address is the braking system. Unlike traditional vehicles that use engine vacuum to power the brake booster, electric vehicles (EVs) lack this natural vacuum source. Therefore, selecting a suitable vacuum braking system—or more accurately, a brake booster solution—is essential for maintaining safe and responsive braking performance.
The 120kW 3-in-1 electric powertrain installed in the Wuling Rongguang mini bus features a PMSM motor with a peak power of 120kW and operates within a voltage range of 290–480V DC, making it a high-performance electric drivetrain. However, this alsomeans the vehicle no longer has an engine to generate vacuum for the brake booster. As such, an electric vacuum pump (EVP) or an electric brake booster (E-booster) must be integrated into the braking system.
- Understand the Braking Requirements
The first step is to evaluate the original braking system of the Wuling Rongguang. Most likely, it uses a vacuum-assisted hydraulic brake system with a brake booster powered by engine vacuum. After electrification, this vacuum source disappears. The replacement system must provide equivalent or better braking force and pedal feel to ensure driver confidence and safety.
- Choose Between Electric Vacuum Pump (EVP) and Electric Brake Booster
- Electric Vacuum Pump (EVP):This is a cost-effective solution that simulates the vacuum created by an engine. It works with the original vacuum brake booster. When the driver presses the brake pedal, the EVP activates to maintain the required vacuum level. It’s compatible with existing hydraulic systems and is relatively easy to install. However, it has moving parts and may require maintenance over time.
- Electric Brake Booster (E-booster):A more advanced and reliable solution, the E-booster (e.g., Bosch iBooster) uses an electric motor to provide braking assistance without needing vacuum. It offers faster response, regenerative braking integration, and better energy efficiency. It also enables advanced driver assistance systems (ADAS) like AEB (Autonomous Emergency Braking).
For the Wuling Rongguang mini bus, which may be used for urban delivery or passenger transport, safety and reliability are paramount. Therefore, an E-booster system is recommended for new electrification projects, despite higher initial cost.
- Compatibility with the Electric Powertrain
The braking system must be electrically compatible with the 385V platform. While the brake booster itself operates on 12V or 24V, the control signals (via CAN bus) should integrate with the vehicle’s overall control system. Ensure the selected system supports CAN communication for monitoring and fault diagnostics.
Additionally, the peak current draw of the EVP or E-booster should not overload the low-voltage power supply. Most systems consume less than 10A at 12V, which is manageable with a properly sized DC-DC converter.
- Redundancy and Safety
A reliable braking system must have fail-safe mechanisms. For example, if the vacuum pump fails, the driver should still be able to apply the brakes manually (though with increased pedal effort). Systems with dual vacuum sensors or backup pumps enhance safety. For E-booster systems, look for redundant sensors and fail-operational designs.
- Installation and Space Constraints
The Wuling Rongguang has limited engine bay space. Choose a compact EVP or E-booster that fits within the available area. Mounting brackets and wiring routing should be planned carefully to avoid interference with other components like the motor controller or cooling system.
- Maintenance and Durability
The system should have a long service life (ideally matching the 20-year design life of the powertrain). Sealed E-booster units typically require less maintenance than EVPs with mechanical diaphragms. Also, ensure the system is IP67-rated or higher to withstand dust and water in real-world conditions.
- Integration with Regenerative Braking
To maximize energy efficiency, the braking system should support regenerative braking coordination. The E-booster can blend hydraulic and regenerative braking seamlessly, recovering energy during deceleration. This requires coordination between the motor controller, BMS, and brake control unit (BCU) via CAN.
Conclusion
For the electrification of the Wuling Rongguang mini bus, a modern electric brake booster (E-booster) is the most suitable choice, offering superior performance, safety, and integration with regenerative braking. If budget is constrained, a high-quality electric vacuum pump with dual sensors and IP67 protection can be a reliable alternative. Either way, ensure full compatibility with the 120kW powertrain, proper CAN communication, and adherence to safety standards. A well-chosen braking system ensures not only compliance but also driver trust in the converted electric vehicle.
