Recuperating power: Charging a prototype Audi e-tron with kinetic energy

Recuperating power: Charging a prototype Audi e-tron with kinetic energy

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Enlarge / A full facet view of Audi’s prototype e-tron SUV.

Megan Geuss

COLORADO SPRINGS, Colo.—Final week, Audi invited a handful of journalists to go for a drive down Pike’s Peak, one in every of Colorado’s many mountain tops that rise greater than 14,000 toes above sea stage.

We rose earlier than daybreak and shuttled up the mountain to a frigid July dawn overlooking the world. Ready for us on the high had been 4 all-electric prototype automobiles, camouflaged in opposition to unscrupulous photographers. They had been new e-tron SUVs, outfitted for a European market however with aspirations of changing into Audi’s American reply to Tesla’s Mannequin X. With 248.5 miles (400km) of vary, a 95kWh battery, and dual-motor all-wheel drive, the automobile has the potential to be an electrical all-terrain car appropriate for ski journeys to Aspen.

Because the solar inched its method up over Kansas, my fingers started to freeze. The three:30am cup of espresso and the winding drive up the mountain and the skinny, dry air all conspired to make me begin feeling a bit sick. I hopped into one in every of these inscrutably embellished automobiles, hoping to take shelter from the high-altitude wind, and rapidly seen contact screens and paddle shifters and skinny, not-yet-legal-in-America side-view cameras protruding of the perimeters of the car the place mirrors must have been.

However the goal of this drive was to not speculate on options, MSRP, and EPA fuel-equivalent numbers (all of that’s nonetheless topic to alter on the US model of the car, which is able to doubtless be launched in 2019). As an alternative, we had been right here to expertise Audi’s newest engineering developments: particularly, the recuperation system that turns what would in any other case be kinetic power, created throughout coasting and braking, into electrical power. These options contribute to a full 30 p.c of the prototype e-tron’s vary.

Two braking programs

Regenerative braking and regenerative coasting are hardly new developments. However Audi’s engineers have spent important time optimizing the latter and getting it to work with the previous in a method that maximizes recaptured power and in addition gives a easy drive.

Regenerative braking

Audi’s e-tron SUV has two braking programs: an digital braking system and a traditional, friction-based braking system. The digital braking system normally responds while you’re merely tapping the brakes: this initiates the regenerative braking system and captures that kinetic power as electrical power.

Nonetheless, if you happen to apply extra power to the brake, the brake management system is aware of you are attempting to make a whole cease and initiates the usual hydraulic braking system. This hydraulic system will not seize any power for you, however it can convey your car to a whole cease.

The change occurs practically instantaneously, and, in our check drive, it was imperceptible to me.

“The management unit detects with how a lot power the driving force is miserable the brake pedal and calculates how a lot braking torque is required inside milliseconds,” an Audi press launch writes. “If the recuperation torque will not be ample, a displacement piston within the brake hydraulics generates further strain.”

Once we had been about midway down the mountain, our driver, engineer Oswin Röder, pulled off the highway to permit the passengers to stretch their legs and change seats. A compulsory brake-check station awaited us, the place a ranger normally makes use of a thermometer to see if you happen to’re vulnerable to burning out your brakes from all of the downhill driving. Audi’s prototype got here in at a cool 48°F (9°C). Röder later invited us to the touch the inside of the wheel on the brake rotor. I confirmed: all that kinetic power that will have develop into warmth had evidently develop into electrical power.

Regenerative coasting: Your automobile robotically is aware of how a lot to recuperate

Like with different battery electrical automobiles, Audi’s system also can recuperate power because it coasts, drawing on the car’s two electrical motors to create brake torque, which begins taking place as soon as you’re taking your foot off the accelerator. You’ve gotten a number of choices right here, too. You possibly can purely coast, which contributes nothing to regeneration. Or you possibly can manually recuperate power utilizing the automobile’s shift paddles, toggling between Degree 1 and Degree 2 settings, which modify how a lot drag there’s on the automobile’s coast.

Moreover, you possibly can set-it-and-forget-it with automated coasting recuperation. This setting attracts on the automobile’s sensors, together with a digicam up entrance, to find out if you happen to’re coming as much as a curve within the highway or a wall of site visitors on the freeway. The system then adjusts the aggressiveness of the regenerative coasting accordingly. The slowing motion of the brake torque on the electrical motors creates what Audi calls a “one-pedal feeling,” the place you possibly can gradual the automobile with out utilizing the brake in any respect. That comes from Audi, after all: not one of the journalists was allowed to drive the prototypes. We had been simply allowed to sit down in them.

Audi says that, with coasting and braking mixed, power is normally being generated throughout 90 p.c of all decelerations.

This appeared true in observe: earlier than the drive, the Audi crew cooked up a small app related to the car’s inner recuperation system, which confirmed us in actual time precisely when Röder was recuperating power, whether or not from the shortage of acceleration or from the brake, and when he was expending power in drive or when he hit the hydraulic brakes.

By the tip of our journey down the mountain, we had pumped roughly 11kWh again into the battery. An Audi press launch says that its regenerative braking system can recuperate as much as 220kW at a time if the driving force applies the brakes once they’re going roughly 60 miles per hour.

All through all this driving, the automobile is continually calculating whether or not the entrance or the rear axle needs to be contributing to deceleration probably the most. Often, the rear axle is the star of the present, however because the automobile takes a flip, it can intelligently transfer some regenerative drag torque to the entrance axle.

In fact, it is good to remember that that is nonetheless only a prototype car and a prototype car with EU specs at that (the specs will inevitably change for the US market, notably these side-view mirrors, barring a stroke of fine sense from the federal authorities).

A couple of notes about the remainder of the automobile, which is able to doubtless change

The drive final week was very targeted: journalists didn’t get to drive the e-trons, and practically each query about non-recuperation options on the automobile was met with the disclaimer that the reply is topic to alter. Extra particulars can be accessible when the SUV is formally introduced on September 17. Nonetheless, we will say that the aerodynamics of the automobile had been a main concern for Audi, to the purpose that these e-tron SUVs had specifically designed wheels that streamlined the hole between the wheel and the rim and specifically designed lettering, additionally for aerodynamic functions.

The side-view cameras additionally caught everybody’s eye. Though I was a skeptic about this, particularly after studying Ars feedback alongside the traces of “mirrors are a easy device, impervious to hacking, that has labored for 1000’s of years!” I now disagree. On this e-tron, the cameras’ fields of imaginative and prescient had been elegantly proven in a small triangular house contained in the side-view digicam’s door, and the picture was method higher than something you’d get with a mirror. Eradicating side-view mirrors does not do a lot for aerodynamic impact at regular passenger car speeds, however it does make freeway driving quieter, and that is a laudable aim.

Plus, good old school mirrors may be “hacked,” too: a good friend of mine was in school when an unknown drunken reveller roundhouse-kicked the side-view mirror off the driving force’s facet of her car. It is a cruder crime than hacking a digicam, however each are solved by ensuring you look over your shoulder while you change lanes (like you have to be doing anyway) in your strategy to the store to get it mounted.

Though we had been principally cruising the winding highway down the mountain slowly, we did get a second on the freeway as we returned to the resort exterior Colorado Springs. Right here, Röder stepped on the gasoline, and like all good electrical automobiles, the acceleration was instantaneous, and the journey was quieter than you’d discover in a gasoline car.

Lastly, sitting contained in the e-tron was very comfy. The inside local weather is augmented with a warmth pump that permits the automobile to recuperate warmth from the battery, yet one more nod to the effectivity of this car. Seats may be heated or cooled, and there was loads of house in each the entrance and the again for my legs and my laptop computer bag. So, as a passenger, the drive was nice. As a driver involved about vary and luxury, I am positive it will be even higher.

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