Regenerative Braking Physics and Energy Recovery
Regenerative braking converts the vehicle's kinetic energy back into electrical energy by operating the drive motor as a generator during deceleration. When the driver lifts off the accelerator (or in one-pedal driving mode, which applies regeneration aggressively without a separate brake pedal input), the motor controller reverses the energy flow direction: instead of drawing power from the battery to apply torque to the wheels, the motor is driven by the rotating wheels, generating AC power that is rectified and fed back to the battery through the inverter. The efficiency of this energy recovery is significant. A well-calibrated regenerative braking system recovers 60–70% of the kinetic energy that would otherwise be dissipated as heat in friction brakes. In urban stop-and-go driving, regenerative braking can recover 15–25% of total energy consumption, extending range significantly compared to non-regenerative driving. Physical limits on regenerative braking torque: the motor's continuous current rating (generating too much regenerative current can exceed motor winding temperature limits), the battery's maximum charge current acceptance (particularly problematic when the battery is cold or near 100% SoC — if the battery cannot accept regenerated current, the regen must be limited to prevent over-voltage damage), and traction limits (regenerative braking torque, like friction braking, is limited by the tire-road friction coefficient — too much regen torque on a slippery surface causes wheel lockup, requiring the regen to be limited by the stability control system just as ABS limits friction braking).