Braking Energy
Braking energy is the mechanical energy that must be removed when a vehicle slows down or descends.
Where the energy goes
For a level-road slowdown, the main change is in kinetic energy, which depends on vehicle mass and the square of speed. A descent can add gravitational potential energy, while aerodynamic drag and rolling resistance remove some energy before the brakes do.
Friction brakes convert their share of braking energy mainly into heat in the discs, drums, pads, and surrounding air. Regenerative braking routes part of the mechanical energy through the motor and inverter toward the battery. The energy stored in the battery is smaller than the mechanical energy removed because tyre, drivetrain, electrical, and battery losses remain.
Braking energy is measured in joules or watt-hours and should not be confused with braking power. Energy is the total amount handled during an event; power is the rate at which it is handled at a particular moment. Two stops can involve the same energy but very different peak power.
For formulas, gradients, and the limits on recoverable energy, see Regenerative-Braking Calculations.