The argus slipped into the passenger seat of the Mercedes Vision EQXX, an electric prototype that has just traveled more than 1,000 km between France and Germany on a single charge. The opportunity to discover the secrets of its performance.
Promise kept! Last January, Mercedes unveiled the Vision EQXX electric prototype and announced a range of over 1,000 km on one charge. To do this, the manufacturer certainly relied on a large capacity battery (a little less than 100 kWh), but also and above all on an energy consumption of less than 10 kWh/100 km.
By way of comparison, an EQS 450+ with a 107.8 kWh battery and a 333 hp rear motor claims 726 km of autonomy and a consumption of 17.1 kWh/100 km in the WLTP combined cycle. Under the supervision of German homologation body TÜV Süd, the Mercedes EQXX has just reached Cassis, in the south of France, from Sindelfingen in Germany, on a single charge along a route of 1,008 km. A few days after its arrival, we slipped on board for a test drive.
The EQXX more accomplished than a simple prototype
More than a concept car or a rolling laboratory, the Mercedes EQXX is a car made for the road. It is a four-seater sedan approved for use on public roads, taking advantage of the few regulatory flexibilities granted to small series vehicles. On board, almost nothing reveals its experimental nature. We notice the aerators with a complex and futuristic design worthy of a concept car or the emergency cut-off control on the ceiling. But, apart from these few details, the cabin is similar to that of a mass production electric car. On the road, no unpleasant whistling, no jolts, and a neat interior finish intended to impress. We will come back to it.
The rear engine delivers its 245 hp (41 hp more than last January) with the vivacity specific to “zero emission” vehicles, under the close supervision of a very considerate ESP. The firmness of the seats and suspension is surprising at first, but it seems consistent with the apparent responsiveness of the steering. Because the EQXX is lively and turns flat. It is the engineer Julien Pillas, specialist in electric motors at Mercedes, who is at the wheel. On the winding roads of the hinterland of Nice as at the motorway toll exit, the latter does not hesitate to demonstrate the dynamic capacities of the car and does not hide his pleasure. However, according to the dashboard, consumption at the end of our trip remains close to 9 kWh/100 km. It’s time to ask our driver and his fellow engineers for a few explanations.
How the EQXX cuts through the air
The history of Mercedes is based (among other things) on a few vehicles that have enabled the brand to set milestones in terms of technical advances. The EQXX is among these according to the manufacturer, and its approval for the road is all the more remarkable. One of the crucial elements of its design is its aerodynamics. The car boasts a Cd (drag coefficient) of just 0.17. In 1938, the Mercedes W 125 which had beaten a speed record of 432.7 km/h with a V12 of more than 700 hp did just as well. But it was a single-seater whose four wheels were faired; the car resembling an airplane wing with a cockpit cut out of it. The 2013 Volkswagen XL1, produced in limited series, did manage to achieve a Cd of 0.19, but it was a small two-seater coupé with faired rear wheels. Today’s best mass-produced cars hover around 0.2.
The front bumper of the EQXX has very little openwork. The front brakes do without cooling ducts, the regenerative braking of the powertrain being able to ensure the vast majority of the decelerations required on a daily basis. Fine vents at the bottom and sides of the front bumper help to guide the air optimally. Behind the bottom vent is a flap that can change position on command to provide additional cooling via a radiator, the hot air then evacuating through the two openings in the hood.
The 20-inch rims are solid, their junction with the tires has been smoothed as much as possible with the help of Bridgestone, which has developed specific rubbers. And extractors are located behind the front fenders. The flag describes a receding curve towards the stern. The rear track is 50mm narrower than the front track. At the rear, a diffuser completes the flat bottom, and this automatically deploys at 60 kph. So despite its reasonable power, the car would theoretically be able to reach around 300 km/h at peak speed according to its designers.
A compact and dense battery for the future
If aerodynamics is crucial (62% of the energy used by a car is only used to counter the relative wind according to Mercedes), the weight is just as important. With 1,755 kg on the scale, or some 700 kg less than an EQS, the EQXX is not light for all that compared to a thermal equivalent. But its 495 kg battery still weighs almost 200 kg less than that of the EQS. It is also compact, measuring 2 m long, 1.26 m wide and 11 cm high.
Classic in its chemistry (lithium-ion), it benefits from cells offering an energy density greater than 400 Wh/l, but also from passive cooling using air which rushes in through the scoop of the front bumper. This configuration could be found on board the next generation compact electric Mercedes, which will be launched from 2025 on a new modular platform dubbed MMA. This would allow the manufacturer to offer small electric vehicles with a long range. Similarly, the voltage of 900 V to quickly recharge the battery of the EQXX (15 min for 300 km according to Mercedes) should find its way to mass production. This will also be the case at Stellantis, starting with the Peugeot 9X8 endurance hybrid.
The obsession with energy waste
The interior of the Mercedes EQXX gives pride of place to materials from recycling or sustainable sources. The seats, for example, are upholstered in white synthetic leather, contrasted by a few touches of pink gold characteristic of the Mercedes EQ models. But what impresses inside is the touch screen that occupies the entire width of the dashboard. These are not multiple monitors grouped together behind a single panel, but rathera unique 47.5 8K display diagonal inches.
Its presence seems to contradict the engineers’ search for energy sobriety. But its backlight comes from a strip of LEDs that turn on or off individually as needed; their consumption is almost nil behind a black element on the screen, which at the same time benefits the visual contrast. Sensors placed at the front of the car detect the direction and strength of the wind, making it possible to finely adjust the range displayed on the screen.
Still with the aim of chasing energy expenditure, the EQXX does not have retro cameras. The advantage of the latter over the Cx is only 0.001 while their cameras and screens consume energy while adding weight according to the engineers. Teddy Woll, head of aerodynamics at Mercedes, also points out that these devices are less effective than good old mirrors. On the one hand, their display accuracy will always be lower than what the human eye can perceive in a mirror. On the other hand, they suffer from a latency which, however small, can be important on the road.
TO READ. Autonomy of electric cars: the results of our tests
Finally, engineers worked to minimize friction, redundant functionality and other energy losses. It starts with the charging socket, which only accepts direct current, or with the tires which, while offering the more than satisfactory grip that we have observed, are studied for minimum rolling resistance. On the roof, 117 photovoltaic cells supply the 12 V battery dedicated to on-board accessories. This solution, already offered by a handful of other manufacturers, makes it possible to gain approximately 2% of autonomy according to Mercedes, which indicates that 95% of the energy of the traction battery reaches the driving wheels of the EQXX.
1,000 km between Germany and the French Riviera
Thus, the Mercedes EQXX which left Sindelfingen on April 5, 2022 at 7:00 a.m. arrived in Cassis the same day at 7:02 p.m. with approximately 15% charge remaining, or approximately 140 km. This represents a consumption of 8.7 kWh/100 km. At an average speed of 87.4 km/h and without exceeding 140 km/h, it traveled through the Alps, crossing Switzerland before taking the Saint-Gothard tunnel to reach Italy and finally fork towards France. . Only two stops were made on the way to change drivers. The Vision EQXX is not intended to be marketed and will continue to evolve, like the Mercedes C111 in its time. But the technologies it embeds will be gradually deployed in production cars.
