The "Pancake" Revolution: Mercedes-Benz Launches Mass Production of Axial-Flux Motors in Berlin

In a milestone event for the automotive industry, Mercedes-Benz has officially inaugurated the mass production of its proprietary axial-flux electric motors at its historic Berlin-Marienfelde plant. This technological shift marks a definitive departure from the traditional radial-flux motor architecture that has dominated the EV sector for over a decade. By moving production to the 1902-founded Berlin facility, the company is effectively transforming the site into a global competence center for high-performance electric drive systems.

The event, attended by Federal Minister of Transport Patrick Schnieder, signals more than just a new product line; it represents a fundamental re-engineering of the electric drivetrain, positioning the new Mercedes-AMG GT 4-Door Coupé as the primary beneficiary of this radical performance leap.

The Technological Leap: Why Axial-Flux?

For decades, the automotive industry has relied on radial-flux motors, where the electromagnetic field is directed perpendicular to the motor shaft. While reliable, these motors often face limitations in power density and thermal management. The axial-flux motor, often referred to as the "Pancake" motor due to its flat, disc-shaped geometry, flips this paradigm. In these motors, the electromagnetic flux runs parallel to the axis of rotation.

The result is a device that is roughly one-third the size and one-third the weight of a conventional motor, yet capable of delivering three times the power density. Mercedes-Benz executives have characterized the technology as the "V8 of the electric age," emphasizing that it replicates the visceral, immediate torque and high-revving nature that enthusiasts once associated solely with internal combustion engines.

Engineering the "Pancake" Design

The structural advantage of the axial-flux design lies in its "sandwich" configuration. Two rotors enclose a central stator, allowing for a much shorter path for the magnetic field. This efficiency reduces energy loss and allows for the massive performance metrics seen in the latest AMG prototypes. The motor’s dimensions are striking: at the front axle, the unit is less than 9 cm wide, while the rear units are roughly 8 cm wide. These are integrated into "High Performance Electric Drive Units" (HP.EDU), which include a compact, single-speed planetary gearbox within the same housing.

Chronology of Development: From Yasa to Industrialization

The journey to the Berlin production line began long before the ribbon-cutting ceremony. The foundational technology was refined by the British electric motor specialist Yasa, which Mercedes-Benz acquired in 2021. Since the acquisition, the Stuttgart-based automaker has spent three years transitioning the technology from a prototype-grade component to a mass-production marvel.

• 2021: Mercedes-Benz acquires Yasa to secure proprietary access to axial-flux technology.
• 2022–2023: Intensive R&D phase focused on thermal management, specifically the development of direct oil-cooling for copper windings.
• 2024: Pilot production testing at the Marienfelde facility, focusing on laser-welding and automated assembly.
• 2026 (Present): Official commencement of full-scale serial production in Berlin.

This timeline reflects a massive commitment to vertical integration. By developing their own production processes, Mercedes has ensured that they do not just own the design, but also the "know-how" to produce these complex machines at a scale previously thought impossible for axial-flux architectures.

Supporting Data: Efficiency and Durability

The performance of the axial-flux motor was not merely tested in a laboratory; it was validated under the most grueling conditions possible. During a series of record-breaking runs at the Nardò technical center in Italy, the Concept AMG GT XX demonstrated the motor’s incredible thermal stability.

Over the course of seven days and 13 hours, the vehicle covered more than 40,000 kilometers, setting 25 long-distance records. Most impressively, the car completed a 10,000-kilometer sprint in just 44 hours. During this time, the car maintained a constant speed of 300 km/h, with charging stops utilizing an 850 kW charging capacity. Even under ambient temperatures of 35°C, the motors showed zero signs of performance degradation—a testament to the superior cooling properties of the direct-oil cooling system, which allows the copper coils to shed heat more efficiently than traditional air or jacket-cooled radial motors.

Manufacturing Innovations: A New Industrial Standard

The production of these motors is a masterclass in modern industrial engineering. Mercedes-Benz engineers had to solve significant hurdles regarding precision, process stability, and automation. According to company reports, the assembly line involves 98 distinct process steps, 65 of which are new to the brand, and 35 of which are global industry firsts.

The Precision of Copper and Laser

One of the most complex tasks is the winding of the stator. To maximize density, Mercedes uses rectangular copper wire instead of traditional round wire. Bending this wire into tight radii without damaging the insulation or thinning the cross-section requires a bespoke automated process.

Once the coils are in place, the connections are finalized using a precision laser-welding technique. This allows for a minimal energy footprint, preventing the heat from damaging the sensitive plastic components surrounding the connection points.

Artificial Intelligence in Quality Control

The factory floor utilizes AI-driven image processing to oversee the "Polymerschweißen" (polymer welding) process. This technology ensures that the plastic housing parts are joined with sub-millimeter accuracy. The AI creates "virtual protection zones," ensuring that the laser energy is directed only at the intended surfaces, resulting in a bond that is both leak-proof and mechanically robust under high-torque stress.

The "Hochzeit" (Marriage) Process

Perhaps the most impressive step is the final assembly, or "Hochzeit." The stator must be positioned between two rotor discs containing high-powered magnets. These components exert a magnetic force of up to 9 kN (approximately 900 kg). To place the stator in the exact magnetic center with a tolerance of less than 0.1 mm, Mercedes employs a high-frequency control algorithm that adjusts the positioning in the final 0.5 seconds of the process. It is a process that relies less on brute force and more on a "digital handshake" between sensors and robotic actuators.

Official Responses and Strategic Implications

Michael Schiebe, who oversaw the project as the former head of AMG and is now the Production Director of the Mercedes-Benz Group, highlighted the strategic importance of this development. "The enormous performance and ultra-fast charging capabilities were consistently available throughout our endurance testing," Schiebe stated. "This technology is the bedrock upon which the next generation of performance electric vehicles will be built."

The implication for the automotive market is clear: Mercedes-Benz is moving to monopolize the "high-performance" electric vehicle segment. By mastering the mass production of axial-flux motors, they are effectively raising the barrier to entry for competitors.

Market Impact

1. Performance Ceiling: With the ability to achieve 300 km/h sustained speeds and 0-100 km/h acceleration in 2.1 seconds, the axial-flux motor redefines what a "sports car" means in the electric era.
2. Manufacturing Sovereignty: By securing over 30 patents for the manufacturing processes alone, Mercedes has created a "moat" around its technology.
3. Future-Proofing Berlin: The transformation of the Berlin-Marienfelde plant from a legacy combustion engine site to a high-tech electric motor hub serves as a model for the rest of the German automotive industry.

Conclusion

The launch of the axial-flux motor in Berlin is more than a technical achievement; it is a declaration of intent. As the automotive industry navigates the transition toward full electrification, the challenge of maintaining the "AMG spirit"—defined by power, soul, and extreme performance—has been a point of contention. With the "Pancake" motor, Mercedes-Benz has found the answer. By successfully industrializing a motor that was previously considered too complex for mass assembly, they have secured a significant competitive advantage. As these motors begin to roll off the lines and into the new AMG GT 4-Door, the definition of electric performance is being rewritten in the heart of Berlin.