Exploring the Mercedes-Benz EQXX: A Concept Car Revolutionizing Electric Efficiency

One significant criticism of electric vehicles is their limited range and slower charging speeds compared to internal combustion engine (ICE) cars. This discrepancy primarily stems from the considerably lower energy content of their batteries compared to traditional fuel tanks.

To enhance the range of any vehicle, there are generally two approaches. The first, and simpler, method involves increasing the capacity of the fuel tank. While this is typically easy and cost-effective for fuel-powered cars, it proves to be much more challenging and expensive for electric vehicles. The second approach focuses on optimizing various aspects of the vehicle, including aerodynamics, rolling resistance, and weight reduction.

The Mercedes-Benz EQXX achieved a remarkable 1,008 km on a single charge, with an energy consumption of 8.7 kWh per 100 km and an average speed of 87 km/h. To achieve this feat, Mercedes-Benz incorporated a large battery and optimized the vehicle’s overall efficiency. Let’s explore how they accomplished this.

Aerodynamics

The primary energy consumer in any car is aerodynamic drag. While this drag is not as significant at speeds below 60 km/h, it becomes the most energy-intensive factor at typical highway speeds. The EQXX boasts a drag coefficient (Cd) of 0.17 and a frontal area of 2.12 m², which results in a total drag area of just 0.36 m², exceptionally low when compared to other models. For example, the Mercedes-Benz EQS, one of the most aerodynamically efficient vehicles currently available, has a total drag area of 0.5 m²—39% larger than that of the EQXX.

Mercedes-Benz achieved this impressive efficiency through targeted design measures. The car features a streamlined waterdrop shape, with a 50 mm narrower rear section, on-demand aero cooling, an elongated tail, and a blend of active and passive aerodynamics. The 20-inch wheels are fully covered to enhance aerodynamic efficiency, as they can contribute up to a quarter of a car's total drag. At a common highway speed of 130 km/h, the power requirements for the EQXX are only 14 PS, an astonishingly low figure.

Powertrain

Mercedes-Benz claims an impressive 95% efficiency for the powertrain, from the battery to the wheels. In the power transfer process, three components contribute to energy loss: the power electronics, the motor, and the gearbox. Achieving such efficiency requires that each of these components exceeds 98% efficiency, a feat not currently attainable in mainstream automotive production.

We can make an educated guess about the motor, likely a synchronous type and probably permanent magnet-based. The motor and power electronics, due to their high efficiency, necessitate minimal cooling. The concept of on-demand (aero and liquid) cooling is employed to further reduce drag and power consumption. The motor is rated for a maximum power output of 180 kW (245 PS), with an estimated torque of around 400 Nm.

Bodywork

To achieve efficiency, lightweight construction is essential. Although electric vehicles benefit from regenerative braking—capturing more kinetic energy the heavier they are—this benefit is negligible during highway travel. The unladen weight of the EQXX stands at 1,755 kg, a notable achievement considering that the high-voltage battery alone weighs nearly half a tonne.

The EQXX is manufactured using aluminum, martensitic steel, and carbon fiber-reinforced plastic, with its wheels crafted from forged magnesium. A pioneering feature of this vehicle is the use of aluminum brake discs, which are lighter than conventional steel discs.

This combination of aluminum brake discs and magnesium wheels significantly reduces the unsprung mass of the car, enhancing both acceleration and ride comfort. All materials used are characterized by their lightness while maintaining high stiffness and rigidity.

Bionic principles have been adopted in the construction process, employing materials only where necessary to avoid excessive use. This philosophy extends into the vehicle's interior, where sustainable and lightweight materials are utilized. In an effort to further improve efficiency, solar cells are integrated into the roof. These cells power low-voltage consumers, such as the infotainment system, air blower, and LED headlights, providing an additional 25 km of range on bright days—though modest, this feature is significant for record-breaking attempts.

High Voltage Battery

The high-voltage battery utilized by the EQXX has a net energy content of 100 kWh and weighs approximately 500 kg. It adopts a cell-to-pack architecture (without modules), is air-cooled, and features a carbon fiber top lid. These attributes contribute to its lightweight design, making it 30% lighter and occupying 50% less volume compared to the high-voltage battery used in the EQS.

Additionally, the EQXX incorporates a >900V architecture, which facilitates ultra-fast charging with supported DC chargers, although passive air cooling currently restricts this capability.

It is generally possible to enhance electrical power either through voltage or current. Choosing the "current" method often incurs a weight penalty due to thicker wiring, making it more sensible to increase the voltage instead.

Mercedes-Benz has also introduced a different anode material compared to the EQS, opting for a High-Silicon anode in the EQXX. This innovation has significantly increased the battery's energy density to 200 Wh/kg, making it the world's most energy-dense high-voltage battery. The carbon fiber lid and air cooling contribute to its compact design, allowing it to be seamlessly integrated into a smaller structure.

Although the EQXX is currently just a concept, the technology utilized in this vehicle holds the potential to be implemented in future Mercedes-Benz production vehicles, which is crucial for advancing e-mobility.