One of the primary criticisms faced by electric vehicles (EVs) is their limited range and slower recharge speeds compared to internal combustion engine (ICE) vehicles. This stems largely from the significantly lower energy content of EV batteries when compared to a conventional fuel tank.
There are typically two approaches to extending a car's range. The first, and simpler method, is to increase the capacity of the fuel tank. While this is usually straightforward and cost-effective for fuel-powered vehicles, it poses considerable challenges and expenses for electric vehicles. The second method involves optimizing various vehicle parameters, including aerodynamics, rolling resistance, and weight reduction.
Mercedes-Benz's EQXX achieved an impressive range of 1,008 km on a single charge, with an energy consumption rate of just 8.7 kWh per 100 km while maintaining an average speed of 87 km/h. Mercedes accomplished this feat by incorporating a highly efficient battery and a streamlined vehicle design. Let's explore how they achieved such remarkable efficiency.
The Mercedes-Benz EQXXAerodynamics
Aerodynamic drag is the primary energy consumer in any vehicle. While this drag is minimal at speeds below 60 km/h, it becomes a significant factor at highway speeds. The Mercedes-Benz EQXX boasts a drag coefficient (Cd) of 0.17 and a frontal area of 2.12 m², resulting in a total drag area of just 0.36 m²—remarkably low. For comparison, the Mercedes-Benz EQS, which ranks among the most aerodynamically efficient cars on the market, has a total drag area of 0.5 m², or 39% higher than the EQXX.
Wind tunnel testing of the Mercedes-Benz EQXXMercedes-Benz achieved this efficiency through targeted design measures. The EQXX features a waterdrop shape, 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 enclosed to enhance aerodynamic efficiency, as they account for up to a quarter of a car's total drag. At a typical highway speed of 130 km/h, the EQXX requires just 14 PS of power due to these aerodynamic innovations—an astonishingly low figure.
At 130kmh the Mercedes-Benz EQXX needs just 14PS because of low aerodynamic dragPowertrain
Mercedes-Benz claims an impressive 95% efficiency from the EQXX's powertrain, from battery to wheels. In this power flow, there are three sources of energy loss: power electronics, the motor, and the gearbox. Achieving this level of efficiency requires each of these components to exceed 98% efficiency, a feat currently unattainable in mainstream automotive manufacturing.
The motor is likely a synchronous type, probably utilizing permanent magnet technology. Due to their high efficiency, the power electronics and motor demand minimal cooling, enabling the incorporation of on-demand cooling systems—both aerodynamic and liquid—to further reduce drag and power consumption. The maximum power output of the motor is 180 kW (245 PS), with torque figures still undisclosed but estimated to be around 400 Nm.
The compact powertrain of the EQXXBodywork
In the pursuit of efficiency, lightweight construction is crucial. Although electric vehicles utilize regenerative braking, during highway driving, its contributions are minimal. The EQXX has an unladen weight of 1,755 kg, a remarkable achievement given that its high-voltage battery alone approaches half a tonne.
The EQXX's body incorporates aluminum, martensitic steel, and carbon fiber reinforced plastic, with forged magnesium wheels. Notably, aluminum brake discs have been employed for the first time, providing a lighter alternative to traditional steel discs.
This combination of aluminum brakes and magnesium wheels significantly decreases the car's unsprung mass, enhancing acceleration and ride comfort. The materials selected are lightweight yet exhibit high stiffness and rigidity, ensuring structural integrity.
The design incorporates bionic principles, utilizing materials optimally to prevent excess weight. Inside the vehicle, sustainable and lightweight materials are used extensively. Additionally, solar cells on the roof are designed to power low-voltage devices such as the infotainment system, air blower, and LED headlights, contributing up to 25 km of range on sunny days—though modest, this feature contributes to overall efficiency.
The rear aluminum construction of the EQXXHigh Voltage Battery
The EQXX utilizes a high-voltage battery with a net energy capacity of 100 kWh and weighs nearly 500 kg. Employing a cell-to-pack architecture (where cells are not organized into modules), this battery is air-cooled and features a carbon fiber top lid. These innovations contribute to its reduced weight, making it 30% lighter and occupying 50% less volume than the high-voltage battery found in the EQS.
The EQXX also marks a first for Mercedes-Benz with its >900V architecture, enabling rapid charging from compatible DC chargers—though passive air cooling limits this capability.
In electrical power systems, increasing voltage or current can enhance performance. Opting for current may necessitate thicker cables, adding weight and size to the vehicle. Therefore, raising voltage is the more efficient choice.
Additionally, the EQXX integrates a different anode material than the EQS, incorporating a high-silicon anode that greatly enhances energy density, achieving 200 Wh/kg—making it the most energy-dense high-voltage battery currently available. The carbon fiber lid and air cooling help to ensure this compact battery design is feasible.
Mercedes-Benz EQXX high voltage batteryWhile the EQXX remains a concept vehicle, the technology utilized could soon be seen in future Mercedes-Benz production models, playing a pivotal role in the advancement and establishment of e-mobility.
