Efficiency is the key to everything - Insight Mercedes-Benz Drivetrains & Efficiency: the short version

Mercedes-Benz is emphasising its claim to leadership in drive systems, including those planned for the future. Customers will be able to choose between two innovative powertrains in the upcoming vehicle architecture. The forthcoming CLA will be available as a highly efficient electric car and as an economical hybrid.

Mercedes-Benz has set new standards in terms of efficiency with the VISION EQXX technology platform. The company is now incorporating the findings from this project into its series-production vehicles. Leading the way is the new all-electric CLA, as the first model to be based on the Mercedes-Benz Modular Architecture (MMA). The centrepiece of this versatile and flexible vehicle architecture is the so-called skateboard chassis, a floor assembly designed primarily for electric cars, including the corresponding drive and chassis components. The body design varies, however: in the newly defined entry-level segment, Mercedes-Benz is planning a family of four models in total. In addition to the CLA as a four-door saloon, these include a shooting brake and two SUVs.

The company will also rely on intelligent modularity with a scalable skateboard design for future model families in other segments. Because Mercedes-Benz is striving for a leading role in both electric driving and vehicle software, the company has massively increased its development activities in these areas. This includes the recent opening of the eCampus in Stuttgart-Untertürkheim as a competence centre for the development of cells and batteries for the future electric vehicles of the brand with the three-pointed star. The aim is to develop innovative chemical combinations and optimised production processes for high-performance cells with "Mercedes-Benz DNA" and thus reduce battery costs by more than 30 percent in the coming years.

Parts of the development and testing of the new MMA models have taken place in the Electric Software Hub (ESH). This building in the Mercedes-Benz Technology Centre (MTC) in Sindelfingen brings together numerous software, hardware, system integration and testing functions under one roof. The entire electrical/electronic integration process of vehicle development is reflected within the ESH. This ensures that all new hardware and software components interact smoothly.

The first MMA model

With its outstanding energy efficiency, the highly flexible MMA architecture marks the next step into the electric future of Mercedes-Benz. The new powertrain incorporates the many years of engineering excellence of the brand with the three-pointed star. This applies equally to the high-voltage components and to mechanical components such as transmissions. The Electric Drive Unit (EDU 2.0) is the first of a new generation of electric drive units from Mercedes-Benz. The highly integrated units form an intelligent modular system.

With the main drive on the rear axle for optimum traction and driving characteristics, Mercedes‑Benz is now introducing a drive layout familiar from the mid-size and luxury classes to the entry-level segment. The 200-kW electric drive unit with a permanently excited synchronous machine (PSM) on the rear axle was developed entirely in-house by Mercedes-Benz engineers. The high-performance power electronics are equipped with a silicon carbide (SiC) inverter for particularly efficient energy utilisation. Transmission control and inverter are highly integrated in a single component. The drive unit is built in Untertürkheim, where Mercedes‑Benz has developed many innovative drives over the years.

The EDU 2.0 reconciles the conflicting goals of maximum torque, top speed and exemplary efficiency, especially in real driving conditions. This is because the high torque ensures dynamic driving performance. It is also helpful when negotiating mountain passes or towing trailers. Another strength is the extraordinary compactness of the EDU 2.0, which benefits the interior dimensions and the volume of the rear boot.

The 4MATIC models also have an 80-kW drive unit on the front axle. In the interests of efficiency, this is also equipped with a next-generation inverter with silicon carbide (SiC) and designed as a permanently excited synchronous machine (PSM). The front electric motor acts as a “boost” drive. Depending on the driving situation or driving programme, it is only switched on when the corresponding power or traction is required. This task is performed by the Disconnect Unit (DCU), which Mercedes-Benz is now using for the first time in the entry-level segment.

For greater efficiency, the DCU can decouple the electric motor on the front axle at lightning speed when the load is low, so that the electric motor and parts of the transmission are at a standstill. This reduces front axle losses by 90 % and increases the range. In the case of the Concept CLA Class, this would correspond to a range of more than 750 kilometres (WLTP) (1). With an energy consumption of just 12 kWh/100 km, the Concept CLA Class would be the ‘one-litre car’ of the electric age.

Mercedes-Benz is using 800-volt electrical architecture for the first time. The system maximises efficiency and performance and, in conjunction with the new battery generation, can significantly reduce charging time. Within 10 minutes, a range of up to 300 kilometres1 can be added to the Concept CLA Class using DC fast charging. Thanks to its focus on time efficiency, the CLA has already done better than other close-to-production electric vehicles in a record attempt: In a 24-hour test drive at Nardò in southern Italy, a pre-series model covered exactly 3,717 kilometres in 24 hours. The two-speed transmission on the main drive on the rear axle not only contributes to efficiency, but also enables extremely dynamic driving performance.

Customers will be able to choose between batteries with two different cell chemistries. The cells of the premium version with a usable energy content totalling 85 kWh have anodes in which silicon oxide is added to the graphite. Compared to the predecessor battery with conventional graphite anodes, the gravimetric energy density is up to 20 % higher. At cell level, the volumetric energy density of the cell chemistry is 680 Wh/l. The use of raw materials has been further optimised and reduced. In particular, the proportion of cobalt has been further reduced.

This is followed by an all-electric entry-level variant with a lithium iron phosphate (LFP) cathode battery. Its usable energy content is 58 kWh and the volumetric energy density of the cell chemistry is 450 Wh/l.

The new hybrid is capable of all-electric driving

Mercedes-Benz is emphasising its claim to leadership in drive systems – whether electric or hybrid. Efficiency is also the key to the development of modern hybrid drive systems. The MMA architecture vehicles will also be available as a hybrid with 48-volt technology. The electric motor with 20 kW drive power (2) has been integrated into a new electrified eight-speed dual-clutch transmission (8F-eDCT) together with an inverter. The electrical energy of up to 1.3 kWh is provided by a new 48-volt battery with lithium-ion technology and a flat-pack design.

Thanks to energy recuperation and all-electric driving capability at urban speeds, this drivetrain is particularly efficient. This is enhanced by electric coasting at a speed of up to around 100 km/h1. The combustion engine is a new FAME (Family of Modular Engines) four-cylinder petrol engine. The hybrid drivetrain is initially available in three power levels with 100, 120 or 140 kW1.

(1) The information is provisional. There are currently no confirmed values from an officially recognised testing organisation, nor an EC-type approval, nor a certificate of conformity with official values. There may be discrepancies between the information and the official values.

(2) The information is provisional. There are currently no confirmed values from an officially recognised testing organisation, nor an EC-type approval, nor a certificate of conformity with official values. There may be discrepancies between the information and the official values.