As you’re driving, the battery supplies the vehicle with power based on your input via the throttle. When you remove your foot from the throttle, the power supply is cut off from the vehicle, meaning you’ll gradually lose power as the vehicle begins to slow down With electric cars, the motor begins to run backwards, capturing the created excess kinetic energy similar to how a generator uses friction. This captured energy used to slow down the vehicle is then stored back in the battery, meaning you’ve slowed your vehicle down and taken back some of the charge you used all at the same time.