Brake System Thermal Performance for Brazil Market Battery Electric Vehicles

The discussion in the braking industry that has been ongoing for over a decade now on how to specify brake systems for regenerative-brake intensive vehicle applications has intensified considerably in the past few years as the automotive industry ponders a future where electric vehicles become predominant. Major automotive manufactures have announced plans to create dedicated electric-only vehicle architectures, from which to offer a full range of electric vehicle configurations. The time to really figure out the translation of Voice of the Electric Vehicle Customer to technical requirements and brake system content is approaching very rapidly. One of the major design decisions in the brake system is the sizing of foundation brake components for thermal performance. There is no question that regenerative brakes can significantly reduce the demand on the friction brakes in normal usage, sometimes by a full order of magnitude or more. Brakes no longer need to be sized for everyday use, rather, the sizing is driven by “limit cases” such as failure of the regen system, a full state of charge in the battery at high elevation, or conditions of “de-rating” of regenerative braking due to drive motor and/or battery operating conditions including temperature. The present work takes an in-depth look at real world vehicle operating conditions that can drive high thermal loads to the brakes and proposes requirements and methodology for relating this to brake hardware selection. The methodology is illustrated through case studies and analysis, showing how brake temperatures are affected by changing from an internal combustion to an electric drive, and further showing how factors such as initial battery state of charge can have a significant effect on the brake temperatures.