E-mobility Mercedes unveils the powertrain of the new CLA

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With a new drive unit, 800-volt system, and silicon carbide inverter, Mercedes aims to set new benchmarks in efficiency for the MMA models. The new CLA thus achieves a range of more than 750 kilometers (470 miles).

The new Mercedes-Benz CLA will be launched next year as an electric vehicle and as a hybrid. In doing so, Mercedes brings its findings from the technology carrier Vision EQXX. The CLA is the first model to be based on the Mercedes-Benz Modular Architecture, or MMA for short. The core of this flexible vehicle architecture is the so-called skateboard chassis, a platform primarily designed for electric cars with the corresponding drive and suspension components. The body, on the other hand, varies: In the newly defined entry-level segment, Mercedes-Benz plans a family of four models in total. In addition to the CLA as a four-door sedan, these include a Shooting Brake and two SUVs.

Parts of the development and testing of the new MMA models took place in the Electric Software Hub (ESH). In this building at the Mercedes-Benz Technology Center (MTC) in Sindelfingen, numerous functions related to software, hardware, system integration, and testing are combined under one roof. Inside the ESH, the entire electrical/electronic integration process of vehicle development is reflected. This is how Mercedes intends to ensure that all new hardware and software components work together smoothly.

The electric drive unit EDU 2.0

According to the announcement, the new powertrain embodies the brand's longstanding engineering excellence. This applies equally to high-voltage components and to mechanical parts such as the transmission. The new electric drive unit (Electric Drive Unit—EDU 2.0) is a modular system of various highly integrated units. Furthermore, EDU 2.0 represents the first system of a new generation of electric drive units from Mercedes-Benz.

With the main drive on the rear axle, Mercedes-Benz is adopting a drive layout known from the mid-range and upper class in the entry-level segment. The 200 kW e-axle with a permanently excited synchronous machine (PSM) on the rear axle was completely developed by Mercedes. The power electronics are equipped with a silicon carbide (SiC) inverter for particularly efficient energy use. The transmission control and inverter are combined in one component. The drive unit is produced in Untertürkheim/Stuttgart (Germany).

According to Mercedes, the EDU 2.0 resolves the trade-off between maximum torque, top speed, and high efficiency, especially in real driving conditions. The high torque not only ensures dynamic driving performance but is also helpful for tackling gradients on mountain passes or towing loads. Another strength is the compactness of the EDU 2.0.

Markus Schäfer: Close to the "one-liter vehicle of the electric age"

The all-wheel drive models additionally feature an 80 kW drive unit on the front axle. This is also equipped with a SiC inverter and designed as a permanently excited synchronous machine. The front e-motor acts as a "boost" drive. Depending on the driving situation or program, it is only engaged when there is a corresponding power demand or traction requirement. This task is performed by the so-called Disconnect Unit (DCU), which Mercedes is now using for the first time in the entry-level segment.

In favor of higher efficiency, the DCU can decouple the e-machine at the front axle under low load, causing the e-motor and parts of the transmission to stand still. This reduces the front axle losses by 90 percent and increases the range. For the "Concept CLA Class," this corresponds to a range of more than 750 kilometers/466 miles (WLTP) with an energy consumption of 12 kWh/100 km (62 miles).

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"With the upcoming MMA vehicles, we are getting closer to the idea of the one-liter vehicle of the electric age," says Markus Schäfer, Member of the Board of Management of Mercedes-Benz Group AG and Chief Technology Officer, Development & Procurement.

Mercedes brings 800-volt architecture

For the first time, Mercedes-Benz is relying on an 800-volt electrical architecture. The system can significantly shorten charging time in conjunction with the new battery generation. Within ten minutes, the "Concept CLA Class" can recharge a range of up to 300 kilometers (190 miles) using DC fast charging with up to 320 kW. For AC charging, the architecture offers options for an 11 kW or 22 kW AC charger.

Thanks to its focus on time efficiency, the CLA has already surpassed other production-based electric vehicles in a record attempt: During a 24-hour test drive in Nardò, southern Italy, a pre-production model covered exactly 3,717 kilometers (2,309 miles) within 24 hours. The two-speed transmission on the main drive at the rear axle contributes not only to efficiency but also enables very dynamic driving performance.

Two types of batteries with different cell chemistries

Customers will be able to choose between batteries with two cell chemistries. 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 has been 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 improved and reduced. In particular, the proportion of cobalt has been decreased.

For the all-electric entry-level variant of the CLA, a battery with lithium iron phosphate cathodes (LFP) is planned. There, the usable energy content is 58 kWh and the volumetric energy density of the cell chemistry is 450 Wh/l.

Hybrids with 48-volt technology

The vehicles of the MMA architecture will also be available as hybrids with 48-volt technology (mild hybrid). The electric motor with 20 kW of drive power, along with an 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 with lithium-ion technology in a flatpack design.

The engine and transmission design are very compact due to the small cylinder spacing and side-by-side arrangement of the e-machine. According to Mercedes, this powertrain is particularly efficient through 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 (62 mph).

"Our new hybrid drive with an electric transmission also sets new standards in terms of efficiency," says Markus Schäfer.

A new four-cylinder gasoline engine with a displacement of 1.5 liters is used as the combustion engine. The unit, with the designation M 252, belongs to the modular engine family FAME (Family of Modular Engines). Initially, three output levels will be available with 100, 120, or 140 kW. In addition, 20 kW of electric drive power is provided.

*Claus-Peter Köth is Editor-in-Chief of 'Automobil Industrie' (German Edition)