Mercedes-Benz Vision EQXX First Ride: Mercedes’ Megameter EV

Behold the most efficient Mercedes ever: the Vision EQXX. On Tuesday, April 5, this experimental concept car drove 626 miles—or 1,007 km, just over a megameter—from its birthplace in Stuttgart, Germany, up and over the 6,900-foot Gotthard Pass in Switzerland to the French Riviera on a single 100-kWh battery charge. The car averaged 56 mph by strictly adhering to all speed limits, peaking at 87 mph on a no-limit stretch of autobahn. They made two 15-minute bio-break stops, arriving in Cassis having consumed only 88 percent of the battery with 87 miles of range remaining (certified by German TÜV authorities). We traveled to the Nice design center that penned the exquisite EQXX to learn how this impressive feat was accomplished and to get a sense of how close the forthcoming EQC sedan might come to achieving similar results.

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Prioritizing Efficiency Efforts

The overarching goal set for the EQXX team was to achieve a single-digit kWh/100 km consumption figure (9 kWh/100 km=233 mpg-e). The Riviera Run yielded an overachieving 8.7 kWh/100 km (241 mpg-e). The team prioritized its efforts proportionately to the forces acting on such an electric compact sedan at speed: 62 percent of the energy expended goes to overcome aerodynamic forces, 20 percent to overcoming the vehicle's weight and rolling resistance, and 18 percent goes to drivetrain losses.

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Lowest Drag Without Fender Skirts

Aero was obviously the development team's No. 1 priority, and wheels are a huge problem (front wheels typically create one-third of a sedan's aero drag). The easiest (and ugliest) way to fix this is by faring the wheels into the bodywork with skirts or spats, but the team in Nice managed to minimize wheel drag with very smooth, unvented wheel covers, by specifying the tire sidewall contours and demanding all labeling be carved into the rubber, not embossed on it, and by insetting the rear wheels almost 2 inches relative to the fronts, putting them in the "wind shadow" of the front wheels. The considerable plan-view taper of the greenhouse makes possible those sensuous rear shoulders that mask this "design don't" (it also benefits aero), but at considerable cost to rear seat shoulder room.

The next biggest aero advance (good for 0.01 Cd) is the rear diffuser, which extends almost 8 inches and drops down 3 degrees at speeds above 35 mph to work with the rest of the sharp edge that rings the tail of the vehicle to manage airflow separation and minimize drag-inducing turbulence. The rest of the story is more conventional: smooth underbelly and A-pillars, smaller, more aerodynamic mirrors, an underbody "cooling plate" that rejects heat directly to air passing under the car, meeting most of the vehicle's cooling needs so the conventional radiator need only be used for climate control or extreme heat. That's fed by shuttered openings in the lower grille that exhausts air through hood vents. The end result: a drag coefficient below 0.17 and a frontal area of 2.10 square meters for a total drag reduction of 29 percent relative to the EQS sedan (0.20, 2.51 sq m).

Weight Savings

Mercedes claims the EQXX tips its scales at 3,870 pounds—a bit less than the 3,902-pound single-motor Tesla Model 3 Long Range we weighed in 2017 with a smaller 75-kWh pack. A more energy-dense battery pack that relies on passive cooling is partly responsible. At 1,091 pounds including the one-box charger/controller, it weighs about the same as a Model 3's actively cooled 75-kWh pack. The body structure employs a megacasting in the rear that, unlike the one in the Tesla Model Y, features "bionic design." The team utilized ZBrush "digital sculpting" software (like Disney/Pixar used to render Shrek) to shape this megacasting, as well as the cast front shock towers, die-cast rear shoulder-belt anchors, and the 3-D-printed aluminum windshield wiper motor support. These parts only feature metal where mechanical stresses require it, with lightening holes where no stress flows. Where necessary, these holes are covered by UBX polymer panels produced from post-consumer waste. There are also composite springs, a carbon-fiber rear motor carrier, and aluminum brake rotors.

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Motor/Battery Optimization and Solar Roof

Mercedes has yet to divulge full specifications on the EQXX's battery and motor, except to say that they operate at 900 volts to further reduce amperage, cabling size (and mass), and overall system losses. The battery still utilizes nickel-manganese-cobalt chemistry employing high-silicon anodes and is said to deliver 95 percent of input energy to propulsion (90 is more typical). The 241-hp Mercedes-developed eATS 2.0-based motor employs a novel stator winding leveraging Formula E technology that places more copper near the rotor for greater power and efficiency. The roof and rear window area are covered in 19.4 square feet of 25 percent efficient photovoltaic panels intended to largely power the infotainment and other non-propulsion systems, extending the car's range by up to 16 miles on a sunny day.

Riding Along in the EQXX

As engineering development vehicles developed from scratch in 18 months go, this one seemed uncannily production ready. Its 47.5-inch 8K-resolution pillar-to-pillar micro-LED (not OLED) screen rendered dazzling navigation info, with an intuitive interface and zero-lag responsiveness. Five different data-visualization tech screens displayed oodles of engineering and eco-coaching info in sharp gamer graphics. The sun's angle of incidence and wind direction are used to precisely forecast solar energy gain, and the aerodynamic effects, the road grade, and traffic forecast help estimate instantaneous range remaining throughout the journey.

And the navy and white interior design is concept-car eye-popping while demonstrating a host of new eco-friendly materials (bamboo-based carpet, vegan "leather" from cactus and mushroom materials, and textiles spun from E. coli-produced faux silk) appear to meet luxury expectations right now. The level of noise and vibration could use a tiny bit of work, but the suspension soaked up bumps with reasonable comfort, and the car cornered nice and flat. Performance seemed roughly on par with that one-motor Tesla Model 3. On the downside, the low-energy, "personal listening" headrest speakers didn't deliver Burmester fidelity, the back seat is laughably unusable, one must duck under the low door frames, and we didn't get a peek in the trunk.

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Might the Next C-Class Be a Megameter Mileage-Master?

The EQXX is sized like the forthcoming MMA-architecture C-Class, but a production version won't go as far on 100 kWh. Simply raising the roof and widening the rear track and/or greenhouse sufficiently to provide a competitive rear seat will erode much of the EQXX's aerodynamic superiority. Engineers describe the EQXX technology as a third production-ready now, one-third coming soon, and one-third completely experimental. We wonder whether unvented wheels and aluminum rotors can pass braking durability testing in a production car. The passively cooled battery is limited to 100 kW charging power, which may not be deemed commercially sufficient. And finally, it must lose another few drag counts each for putting rain gutters on the A-pillars and making the mirrors comply with size and rain-shedding requirements. But we'll call it a huge win if it looks at least a little like this—inside and out—and goes 450 miles on 100 kWh.