What is Regenerative Braking Efficiency?
Regenerative braking is a critical technology in modern electric vehicles (EVs) and hybrids. It allows a vehicle to recover a portion of its kinetic energy during deceleration, converting it back into electrical energy stored in the battery. The efficiency of this process is the ratio between the energy successfully stored in the battery and the total kinetic energy lost during the braking event.
How to Use the Calculator
To determine the efficiency of your vehicle's recovery system, you need four key data points:
- Vehicle Mass: The total weight of the car, including passengers and cargo (in kilograms).
- Initial Speed: The speed at which you began the braking process (in km/h).
- Final Speed: The speed after braking. If you came to a complete stop, this is 0.
- Energy Recovered: The amount of energy reported by your vehicle's telemetry as captured during the event (in Watt-hours).
Understanding the Science
The theoretical kinetic energy lost is calculated using the formula: 1/2 × mass × (initial velocity² - final velocity²). Since speed is often measured in km/h, we convert it to meters per second for the calculation. The energy recovered is then compared against this change in kinetic energy. Note that 100% efficiency is physically impossible due to losses in the electric motor, inverter, battery chemical resistance, and mechanical friction.
Frequently Asked Questions
Why is my efficiency low? Efficiency can be affected by external factors like cold battery temperatures, high states of charge (where the battery cannot accept more power), or aggressive braking that engages traditional friction brakes.
What is a good efficiency rating? Most modern EV systems achieve between 60% and 80% regenerative efficiency under optimal conditions.