Four teams, one mountain, over 200 corners, and one mission! I’m standing on top of Pikes Peak in Colorado, one of the most famous mountains in the United States.For over 100 years, people have been flocking to the top of Pikes Peak, many of them for the hill climb race “Race to the clouds”. But today, I’m not here with the goal of racing to the top of Pikes Peak; I’m here to drive down it while saving as much energy as possible. It’s still dark as we begin the drive to the peak. Through the beams of the headlights of the Audi Q7, I can clearly see the wind blowing the fog away.
The Audi e-tron prototype in a recuperation test
Electric mobility has had an impact on many things, including the tradition of the Pikes Peak race. This time, Audi’s goal wasn’t to reach the summit first—it was to recover as much energy as possible on the descent using recuperation. Find out how much energy the Audi e-tron prototype fed back into the battery on this journey, and what really impressed blogger Des Sellmeijer at the finish...
Pikes Peak from a different perspective
Climbing towards the top at 4,302 meter above sea level, it’s not only the temperature that drops to just above freezing. The oxygen levels also fall to the point that we feel breathless after only a few steps. As we approach the top and the darkness slowly makes way for the first shimmers of dawn, we get our first glimpse of the vehicles for today’s mission: a pack of brand new Audi e-tron prototypes. Now it is our challenge to drive down the mountain and recuperate as much energy as possible using the new fully electric Audi.
What recuperation depends on
“We” are Team Red, made up of myself, Gregor Habermehl from the Motor Presse Stuttgart, and the Head of Audi Break Development for the new fully electric car. The latter sits at the wheel, while Gregor and I keep an eye on the iPad that shows us all current driving data in real time. For example, it can show us our driving route, whether we are coasting, or how hard we are braking. It also shows how many kilowatt hours we have recuperated with the Audi e-tron prototype. I learn something new right at the beginning of the drive: the amount of energy that can be recuperated during the descent depends not only on the car’s hardware and speed, but also its weight. Unfortunately, my joking suggestion to put a few rocks in the trunk doesn’t go over so well with the rest of the team. 😉
Foot off the accelerator to turn energy production on
We set off as the clock hits 6 a.m. The sun rises slowly and the clouds disappear, unveiling a stunning panorama. Silently, the e-tron prototype rolls away from the parking lot, requiring only a touch of the accelerator to reach the beginning—or the end, if you wish—of the Pikes Peak mountain road. From here, it goes downhill for the next 30 kilometers.
The Audi e-tron prototype can recover energy in two ways: by coasting recuperation—when the driver releases the throttle—and during braking. The recuperation system involves both electric motors as well as 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.
The result: every kilometer driven downhill adds about a kilometer of additional range.
Braking with the electric motor
Our descent, and the maximum recuperation challenge, begin. The slope is steep from the very beginning, and we have to reduce our speed with the conventional brakes. In 90 percent of all braking maneuvers, the Audi e-tron prototype uses the electric motor to decelerate. The means that the energy from all normal braking maneuvers is fed back into the battery.
The transition between electric and hydraulic deceleration is smooth, and I would hardly notice it if it weren’t for the fact that the iPad in my hands—my virtual cockpit—lights up red to notify me.Going downhill and acting like a small power-plant is nice, but I would love to see a bit of the e-tron prototype’s performance as well. So, on the flat sections, our Audi colleague puts his foot down and lets the 265 kW and 561Nm of torque from the two electric motors speak for themselves. And I am not disappointed. He fully depresses the accelerator pedal and shifts from drive range D to S, activating the boost mode. For a brief time, the drive produces 300 kW of system output and 664 Nm of torque. Enough for a sprint from 0-100 km/h in less than six seconds and a top speed of 200 km/h.
Brakes as cold as ice
Half-way down the mountain, we are stopped at a mandatory brake check. Here, park rangers check the brake temperatures of each car. If the brakes are over 300 degrees Fahrenheit (148 degrees Celsius) the driver has to park and let the brakes cool down before he is allowed to continue. The Q7 in front of us is measured at 146 degrees F (about 63 C) and is good to go. I wonder how hot our brakes must be—the iPad clearly shows that we used the brakes a few times to slow down for tight hairpins and after some of our sprints. The result surprises me.
Our brakes are only 53 degrees F (just over 10 C). This confirms that virtually all energy used to slow the car down was converted back into our range. The recuperation system contributes to up to 30 percent of the electric SUV’s range. This gives the e-tron prototype a WLTP range of over 400 kilometers on a single battery charge.
Winner in recovery
Now we are keen to find out how well we did compared to the other teams. We continue down the winding mountain road that takes us through the forest and past lakes on our way to the finish. At the end of the road, which is actually the beginning in most cases, we stop the recording on the iPads and hand them over for comparison with the other teams.
We did the 30 kilometer-long stretch in 1 hour and 16 minutes; not exactly a world record. But during the 1,940 meter elevation drop—from 4,301 meters down to 2,361 meters above sea level—we had the highest total recuperation of all time: 10,267 kWh. Not surprisingly, though, we also burned the most energy while accelerating—so the overall efficiency award goes to the yellow team.
Take charge: Audi e-tron prototype – recuperation test
The Audi e-tron prototype combines enormous power and high efficiency. With a system output of up to 300 kW, the full-size SUV with a fully electric drive accelerates from zero to 100 km/h (62.1 mph) in less than six seconds. In the WLTP test cycle, it covers more than 400 kilometers (248.5 mi) on one battery charge. One important factor for the long range is the most innovative recuperation concept among the competitors. The electric SUV proved this with an impressive performance at Pikes Peak.Read more
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