The global debut of the Audi e-tron is getting closer and the final real-world tests are being run to validate all systems. Of importance is the range possible on a battery pack with a full charge, something which is crucial in getting electrically-powered vehicles (EVs) accepted. ‘Range anxiety’ is something which many people have because they worry about running of electricity and being unable to find a charging station to ‘fill up’

Tests have already shown that the e-tron prototype can cover more than 400 kms on one battery charge and this is possible because its powertrain has a most innovative recuperation concept. This was proven in the Rocky Mountains of the USA where an e-tron prototype demonstrated how its recuperation system is variable and the most efficient among all the competitors.

On its 31-km downhill drive from Pikes Peak, the electric SUV fed so much energy back to the battery that it could even cover approximately the same distance again. The difference in altitude of about 1,900 metre provided the necessary conditions for this. The e-tron prototype can recuperate energy with up to 300 Nm of torque and 220 kW of electric power – more than 70% of its operating energy input. No production model has achieved this up to now.

Each kilometre downhill brings an additional kilometre in range as the recuperation system contributes to up to 30% of the electric SUV’s range. It involves both the two electric motors and the electro-hydraulically 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 e-tron prototype recuperates energy solely via the electric motors, without using the conventional brake – that covers over 90% of all decelerations. As a result, energy is fed back to the battery in practically all normal braking manoeuvres.

The driver can select the degree of coasting recuperation in 3 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.

The wheel brakes are involved only when the driver decelerates by more than 0.3 g using the brake pedal. They respond extremely quickly, thanks to a new electrohydraulic actuation concept. Audi is the first manufacturer worldwide to use this concept in a series production vehicle with electric drive.

What is fascinating about this Audi SUV with electric drive is not just its efficiency but also its performance. Its two electric motors have an output of 265 kW and develop 561 Nm of torque. They can deliver this peak performance for up to 60 seconds. This enables the vehicle to accelerate from standstill to the electronically-limited top speed of 200 km/h several times consecutively without output losses. The maximum drive torque is present within fractions of a second and provides enormous torque. By shifting from drive range D to S and fully depressing the right-hand pedal, the driver can activate boost mode. It is available for eight seconds. Here, the drive produces 300 kW of system output and 664 Nm of torque, making it possible to achieve a 0 – 100 km/h time less than 6 seconds, it is claimed.

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[Chips Yap]

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