Mercedes-Benz CLA Technology: Electric Pioneer with a Hybrid Backdoor

Mercedes-Benz has announced further technical details about the new mid-size CLA model, which is set to come as a purely electric vehicle and as a hybrid. The company aims to incorporate features from the VISION EQXX into series vehicles, they said. The novelties will debut in the fully electric CLA, which is the first model to be based on the Mercedes-Benz Modular Architecture (MMA). The cornerstone is the so-called skateboard chassis, a platform primarily designed for electric vehicles with corresponding drive and chassis components. However, the structure, i.e., the body, varies. In the newly defined entry segment, the Swabians are planning an entire family of a total of four models. Besides the CLA as a four-door sedan, these include a shooting brake and two SUVs.

The platform is intended to score with high energy efficiency. The highly integrated Electric Drive Unit (EDU 2.0) represents the first version of a new generation of electric drive units from the manufacturer and opens up a modular system. With the main drive on the rear axle for high traction and driving characteristics, the drivetrain layout known from the mid and upper classes is adopted and transferred to the entry segment. The 200 kW electric drive unit with a permanently excited synchronous machine (PSM) on the rear axle was fully developed in-house. The power electronics are equipped with a silicon carbide (SiC) inverter for particularly efficient energy use. Transmission control and inverter are combined into a single component. The drive unit is built in Untertürkheim. The EDU 2.0 promises to resolve the conflict between maximum torque, top speed, and efficiency, especially in real driving conditions. The high torque not only ensures dynamic performance but is also intended to help on inclines or when towing.

Compact system conserves trunk volume

The setup is expected to score points for its compactness, benefiting the interior dimensions and the volume of the rear trunk. The 4MATIC models additionally feature an 80 kW drive unit on the front axle, also equipped with a next-generation silicon carbide (SiC) inverter and executed as a permanently excited synchronous machine (PSM). The front electric motor acts as a "boost" drive. Depending on the driving situation or driving program, it is only activated when there is a corresponding power demand or traction requirement. This task is undertaken by the so-called Disconnect Unit (DCU), which is used for the first time in the entry segment. For the sake of higher efficiency, the DCU can quickly decouple the e-machine on the front axle under low load, so that the electric motor and parts of the transmission stand still. This reduces the losses of the front axle by 90 percent and increases the range. For the Concept CLA Class, this corresponds to a range of more than 750 kilometers (WLTP), according to the forecast.
 

The "One-Liter Car" of the Electric Age

With an energy consumption of only about 12 kWh/100 km, the Concept CLA Class is virtually the "one-liter car of the electric age," promote the Swabians. For the first time, Mercedes-Benz relies on an 800-volt electric architecture. The system maximizes efficiency and performance and can significantly shorten charging time in conjunction with the new battery generation. Within ten minutes, a range of up to 300 kilometers could be recharged via DC fast charging. In a record attempt in Nardo, a pre-production model covered 3,717 kilometers within 24 hours. The two-speed transmission on the main drive on the rear axle is said to contribute to both efficiency and dynamic driving performance.

Batteries with two different cell chemistries are available. The cells of the top variant, with a usable energy content of a total of 85 kWh, feature anodes where silicon oxide is mixed with graphite. Compared to the previous battery with conventional graphite anodes, the gravimetric energy density could be increased by up to 20 percent. At the cell level, the volumetric energy density of the cell chemistry is 680 Wh/l. The use of raw materials has been further optimized and reduced. In particular, the share of cobalt has been further reduced. Following this, there is a fully electric entry-level variant with a battery with lithium iron phosphate cathodes (LFP). Here, the usable energy content is 58 kWh and the volumetric energy density of the cell chemistry is 450 Wh/l.

The hybrid can also drive briefly in electric mode

High efficiency is also targeted for hybrid drive systems. The vehicles of the MMA architecture will come hybrid with 48-volt technology. The 20 kW electric motor, along with the inverter, has been integrated into a new electrified eight-speed dual-clutch transmission (8F-eDCT). The electrical energy of up to 1.3 kWh is provided by a new 48-volt battery featuring lithium-ion technology and a flat-pack design. This drive system is promised to be very efficient due to recuperation and the ability to drive purely electrically at urban speeds. This is further enhanced by electric sailing at speeds of up to around 100 km/h. The internal combustion engine used is a new four-cylinder gasoline engine from the modular engine family FAME (Family of Modular Engines). Initially, the hybrid drive is available in three power levels: 100, 120, or 140 kW.