For Mercedes AMG EV power, ‘axial flux' anyone?

Mercedes-Benz is developing a new sports car platform for high-performance AMG electric models. To do that, instead of creating horsepower and torque, the electric vehicle formula required a new level of electric motor technology.

"Today, AMG cars have characteristic performance with V-8s," Mercedes-Benz Chief Technology Officer Markus Schäfer told Automotive News. But in the future, he said, the battery power variants must offer "authentic AMG performance and feeling and handling."

To achieve its aim, Mercedes is leaning on a British startup.

Yasa has developed a high-torque, lightweight e-motor that delivers more power with greater efficiency. Last summer, Mercedes-Benz acquired the Oxford University spinoff, securing access to its axial flux technology.

Also called "pancake motors," axial flux motors can generate more torque, have fewer thermal management issues and use fewer materials — reducing overall weight and cost.

The main difference is that the magnetic flux travels parallel to the motor rotation axis in an axial motor, rather than perpendicularly in radial flux motor designs.

Schäfer described Yasa's motor as a high-performance, compact, lightweight electric engine. The motor is about half the size or less of a radial motor, but its energy density per kilogram of motor is "factors higher," he said.

Sam Abuelsamid, principal analyst at Guidehouse Insights, said the axial flux motor's compact footprint allows for more creative packaging.

"They can be placed closer to the wheels," he said.

Yasa's electric motor technology is an evolution in e-motor design. An axial flux motor has a larger diameter because it turns alongside the stator rather than inside it. The larger radius delivers more torque for the same force.

Yasa's motor removes the stator yoke, which helps reduce the iron mass by up to 80 percent.

The company claims that this innovation increases power density by more than 30 percent and delivers a 5 percent range benefit over radial electric motors that typically power mass-market EVs.

Yasa founder and Chief Technology Officer Tim Woolmer said he came up with the idea five weeks into his Ph.D. program at Oxford University.

"I suddenly realized there was a much better way to build an electric machine called a torus axial flux motor," Woolmer said. "The insight I had was that by removing the motor's stator yoke and splitting it into segments, we could reduce the motor's weight — and yet at the same time improve its torque, power density, efficiency and manufacturability."

Mercedes will build axial flux motors at a repurposed combustion engine factory in Berlin.

The motors will power Mercedes-Benz's AMG electric-only platform and potentially other future models.

Schäfer revealed that the axial motor would be paired with a new battery technology that will offer super-fast charging.

He declined to elaborate on the battery tech.

"The whole game is to get the energy to the motor as quickly as possible," Schäfer said. "It's going to be something different."

Mercedes is not alone in its interest in this new tech.

Yasa's axial flux motors have been tapped for other plug-in hybrid supercars, including the Koenigsegg Regera and Ferrari's first plug-in hybrid, the SF90 Stradale.

Meanwhile, Renault has partnered with Whylot to use axial flux motors in its hybrids starting in 2025.

EV motor technology is in its relative infancy, Woolmer told Automotive News Europe.

"The electric motor is no longer seen as a commodity," he said. "There's a huge R&D race to make the motor smaller and lighter, more efficient and low cost."