The scenario: Each kilometer downhill brings around an additional kilometer in range
At 4,302 meters (14,115 ft), Pikes Peak looms high in the southern Rocky Mountains. Where Walter Röhrl won the world’s most famous hill climb in the Audi Sport quattro S1 back in 1987, it is the Audi e-tron prototype that is now causing a sensation with its recuperation system that is variable and thus the most efficient among all the competitors. On its 31 kilometer (19 mi) downhill drive, the electric SUV feeds so much energy back to the battery that it can cover approximately the same distance again. The difference in altitude of about 1,900 meters (6,233.6 ft) provides the necessary conditions for this. The Audi e-tron prototype recuperates energy with up to 300 Nm of torque (221.3 lb-ft) and 220 kW of electric power – more than 70 percent of its operating energy input. No series production model has achieved such a value up to now.
The recuperation concept: from freewheeling to a one-pedal feeling
The recuperation system contributes to up to 30 percent of the electric SUV’s range. It involves both the two electric motors and the electrohydraulically integrated brake control system. For the first time, three different recuperation modes are combined: manual coasting recuperation using the shift paddles, automatic coasting recuperation via the predictive efficiency assist, and brake recuperation with smooth transition between electric and hydraulic deceleration. Up to 0.3 g, the Audi e-tron prototype recuperates energy solely via the electric motors, without using the conventional brake – that covers over 90 percent of all decelerations. As a result, energy is fed back to the battery in practically all normal braking maneuvers.
The driver can select the degree of coasting recuperation in three stages using the steering wheel paddles. At the lowest stage, the vehicle coasts with no additional drag torque when the driver releases the accelerator pedal. At the highest stage, the electric SUV reduces the speed noticeably – the driver can slow down and accelerate using only the accelerator pedal. This creates the one-pedal feeling. There is no need to use the brake pedal in this deceleration scenario.