Automotive supplier Continental has introduced its ‘Green Caliper’, a brake caliper and disc designed specifically for EVs. It saves up to five kg of unsprung weight per wheel and further improves efficiency by reducing residual brake force after releasing the pedal.
The Green Caliper is designed with EVs in mind and optimizes weight and efficiency by looking at the specific braking characteristics of an electric vehicle. According to Continental, the electric motor takes over 80% of all EV decelerations and recuperates the kinetic energy. But the conventional brakes are still needed in emergency stop situations, with more performance required due to the higher mass of battery-electric vehicles.
Less weight, more stopping power
Therefore, these EV-specific brakes need to sap less energy when they’re not required but perform better in rare situations when they are. To achieve this, Continental has developed a smaller caliper design with thinner brake pads, reducing weight, which works in conjunction with a larger, thinner brake disc.
This design saves up to five kg per wheel, improving efficiency and ride due to its unsprung weight, while the larger brake disc enables the caliper to decelerate harder due to the longer lever arm. Of course, this also assumes the EV has larger wheels that fit the Green Caliper brake system – the example Continental uses compares a 375 x 9 mm brake disc to a more standard 330 x 30 mm disc.
Ready for production
Further efficiency is gained by actively retracting the brake pads after braking, reducing residual braking force after the pedal has been released, and thus reducing energy usage. In a regular car, this design would result in grabby brakes, which overheat after heavy use, for example, by going down a mountain road in a fully-loaded car during the family holidays.
In an EV, however, the electric motor recuperates most of the work, while a brake-by-wire system can ensure a smooth transition between regen and disc braking.
Continental says the Green Caliper design is ready to be integrated into electric vehicle design, with a lead time of two to three years before it reaches the road. It’s not the only EV braking innovation out there, with Hitachi showing a hub motor design that integrates the brakes.