Energy recuperation is hugely important to electric vehicles.
To prove how well the technology has come along, Audi invited me to ride along in a prototype Audi e-tron driving down from the summit of Pikes Peak.
Audi have not yet officially revealed the e-tron, but they disclosed the specs on the European Market Prototype that I rode in down the mountain – Disclaimer: THIS IS A EUROPEAN PROTOTYPE. Not only is it pre-production, but it is pre-production for a different market. While this prototype felt and looked very production ready, there is still plenty of time to tweak things before the reveal on September 17, 2018.
That being said, the model we were riding in had a 95kWh battery pack and two electric motors that combined for a total power output of 300kW – roughly 400 horsepower. Audi claims this setup will deliver the e-Tron to 60 MPH in 6.1 seconds.
Here is the challenge: take a battery depleted e-Tron from the top of Pikes Peak and drive it to the bottom, trying to regenerate as much battery as possible along the way.
Crunching the numbers
My ride started with 62% battery remaining and 151km of range left, according to the trip computer. The amount of battery we recuped was all up to the driver’s ability to navigate Audi’s regenerative brake settings. Fortunately, my driver was Marko Hörter who was the project manager on the e-Tron’s brake integration team. Seeing how he lead the project that would play a large part in how much energy we got back, I figured I was in good hands.
The e-Tron can send power to either axle if it deems it necessary. But, in normal driving conditions, the E-Tron appropriates 75% of its power to the rear axle, because the rear motor is larger. As a result, 75% of regenerated energy also comes from the rear axle.
The Audi e-Tron has three regeneration modes. There is ‘Coast’ mode, which minimizes regen when off the accelerator pedal, mode 1, and mode 2. Mode 2 has the most aggressive regenerative braking setting when taking your foot off the go pedal. I should note, the e-Tron can be driven with one foot, as the regenerative braking will bring it to a complete stop. Though, the decelerating force from simply lifting off the accelerator is nothing compared to a Nissan Leaf or BMW i3. This is because the Audi E-Tron uses regenerative braking as the main stopping force behind the brake pedal.
Different approach to braking
Audi did some research and learned that only 10% of brake applications would require a braking force hard enough to necessitate using the actual brakes. Unless you exceed 0.3g of braking force, the e-Tron solely utilizes regenerative force to brake the car, resulting in less energy wasted as heat in the brake pads.
We reached the half-way point down the mountain, Glen Cove, where the Pikes Peak organization has a mandatory brake check set up. The average car usually has a brake temp somewhere around 150 degrees Fahrenheit by this point. If the brakes are hotter than 300 degrees, drivers are asked to park and wait for their brakes to cool down before proceeding. I asked the park ranger what the hottest temp he recorded was, “somewhere around 800, 900 degrees”, he said.
How were the e-Tron’s brakes? They measured a cool-to-the-touch 45 degrees Fahrenheit. The concrete measured 32 degrees. Basically, Marko had not touched the physical disk brakes outside of parking the e-Tron once or twice. Regen was the only force keeping us from flying 2,000 feet to our demise. If you are wondering why I said “cool-to-the-touch”, I literally touched the brake disks, and they were cold.
Completing the Journey
We continued on our merry way down the mountain until we reached the gate, marking the end of our test route. In total, we drove 18 miles, lost 6,350 feet in elevation and gained a significant amount of range. By the bottom, our range had jumped from 151km to 260km (94 to 162 miles). That means we gained 3.72 miles of range for every mile we drove downhill.
Audi gave us a large iPad that displayed realtime data streamed from our car during the run. After completing our downhill portion, we were given a readout that said we recuperated 12kWh of battery in total. That works out to roughly 12.6-percent battery regenerated over the course of the run.
Audi have still not released a whole lot of information about the 2019 Audi e-Tron. We will surely find out a lot more come September 17, when Audi has plans the car’s official launch.
We will be covering the Audi e-Tron as it gets closer to launch. Stay tuned to TFLcar.com for all the latest news, views & real-world reviews and, of course, more videos on the 2019 Audi e-Tron!