Electric vehicles have made people see the possibilities for sustainable development of the automotive industry in the future, and they have also filled people with anxiety about mileage. The Mercedes-Benz EQXX battery, although smaller than the EQS,000, can achieve a longer range of 1,000 kilometers. And all thanks to excellent aerodynamic design.
Driving forward is a battle against air resistance. From 100 km/h upwards, air resistance is the main factor hindering the car's travel, and this resistance is proportional to the square of speed: the seventh-generation Volkswagen Golf needs to use 7.6 kilowatts of energy consumption to overcome air resistance when driving on country roads. At a speed of 200 km/h, about 61 kW of energy is required.
Without considering other resistances, this alone can drain the battery of compact electric vehicles such as ID.4 after driving for 1 hour or 200 kilometers. As a result, Mercedes-Benz equipped the EQS with a 108 kWh battery with a body drag coefficient of 0.20. Under WLTP conditions, the EQS can travel up to 770 km.
More batteries are not the best solution
The 770 km cruising range is really good, of course, the more the merrier. Mercedes-Benz CEO Con linsong said to his senior developers: "Please fully demonstrate your capabilities!" "A vehicle that can be legally driven on the road and travels with a 4-passenger ride has a range target of 1,000 km per charge, but does not use a larger battery: the battery in the EQS weighs 692 kg and occupies the entire floor between the axles. Therefore, energy consumption must be reduced to single digits (less than 10 kWh/100 km), and the vehicle must have ultra-high efficiency. So it all went back to square one.
The question is how exactly to develop such an ideal streamlined car? Teddy Woll, head of Aerodynamic R&D at Mercedes-Benz, and Stefan Lamm, senior head of design, replied that colleagues in the departments of dimensional design, design and aerodynamics were required to work together and conduct relevant tests. According to Wall, it usually takes about a year just to finalize a new car. However, it took colleagues only 6 months to complete the training of the Vision EQXX.
Of course, always be "fair and constructive," Ram said. It's true that there are times when the body size can't be changed, so everyone needs to be prepared to make some compromises. "The resistance coefficient we set in the early stages was 0.15, which may even be lower." However, aerodynamicist Teddy Wall and designer Stefan Ram eventually agreed that even a drag coefficient of 0.15 could not be achieved. Ram vetoed the option of using too narrow and too long a rear. Although we have to make some compromises on the status quo, we must also propose better solutions. Wall sees such debates as not only exciting, but also fruitful. Therefore, it can be expected that the EQXX will use active components in the rear. The developers did not tell us whether the car would be as extreme as the 2015 Mercedes-Benz concept IAA. The concept car extends the rear by 39 cm with an expandable panel and features an active retractable diffuser at the rear to sort out turbulence in the air.
Both developers still remember very clearly that heated discussion about the rear wheel. "What we want is not an experimental car, but a car that is very close to mass production." Vehicles with narrower wheelbases don't look aesthetically pleasing enough, Ram said, and they can also negatively impact driving behavior. Wall stressed: "The stability of driving depends on the suspension on the rear axle, and perhaps no one wants to make it narrower except for us aerodynamicists." In the end, they found a satisfactory solution not only in terms of aerodynamics but also in terms of aesthetics: the body sidewalls were optimised with aerodynamics, while guaranteeing a sufficiently wide rear track.
Speed and range
Those who are concerned about driving performance may suggest that the EQXX should use its excellent aerodynamic advantages to achieve high speeds, but this is actually ignoring the most important goal: high range. As described at the beginning of the article, the Seventh Generation Golf overcame air resistance with twice the speed (200 instead of 100 km/h, wind resistance coefficient of 0.27) and 8 times the power (61 kW) to drive. The EQS has a better drag coefficient, but the front projection area is larger, consuming 52 kW at 200 km/h compared to 6.5 kW at 100 km/h, which is single digit. In actual driving, however, the EQS consumes more than 20 kWh per 100 km. The wind resistance coefficient of EQXX should be smaller than that of EQS, although it is also above 0.15.
A drag coefficient as low as 0.17 alone is still not enough to reduce energy consumption per 100 km to less than 10 kWh, so if driving for a long time, the cruising speed is preferably less than 100 km / h, and the maximum speed should not exceed 130 km / h.
Endurance and efficiency
But how can we further reduce driving resistance? The front projection area of the front of the car has the same effect on air resistance as the impact from the wind resistance coefficient and ground clearance. We know very well that the EQXX is not a very large SUV. Although there is enough space on the floor for larger batteries, this is a four-seater model with a body length of less than 5 meters. In this compact