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Interview: Schaeffler’s New Permanent-Magnet-Free Motor and Upcoming Solid-State Battery Tech

April 22, 2024

With Jeff Hemphill – CTO Schaeffler Americas

Schaeffler unveiled its latest motor at CES 2024, the Electrically Excited Synchronous Machine (EESM). 

This design doesn’t use any rare earth magnets, instead, we use coils on the rotor and we access or pass the electricity to those coils through an RF sender in the shaft, it’s our unique IP to keep things compact. 

It has a high slot fill factor due to our optimized needle winding process (our 2018 acquisition of German coil winding specialist Elmotec helped this development), and the slot coolers are close to the windings, giving it very effective rotor cooling.

It has high-speed compatibility, space neutrality, a touchless rotor power supply, an adaptable rotor field, and it’s scalable. The motor has shown high performance and cycle efficiency in both WLTC and highway driving conditions.

It’s competitive with a permanent magnet machine, without the mess of mining and shipping these materials.

Schaffler has been sheet metal stamping for many decades, one of the fears we had with the shift to electrification was what do we do with all of these presses? It turns out that they have very high utility in this market too. The housing is a stamped metal sheet, and we use the same presses for our motor and transmission components. One thing that’s unique to Schaeffler, is that we design all of the tooling, we do all of our own stamping, laminations, stacking in the press, and then wind our proprietary coils. This all happens at one table, not only product design engineers but also process engineers all working together.

Can you talk about the power density and losses? 

With this design, we’re in control of the magnetic field strength, which allows you to do active field weakening in a much more controlled way than with permanent magnets. 

For example, the higher the motor spins, the more the electrical fields fight you. Because we’re in control of those, we can then back them off at higher speeds if needed. We use this to make up for the efficiency loss that comes from having to electrically create the magnetic field you would normally have with magnets. With this, we get back to the same high-performance level of a permanent magnet motor, even though we’ve introduced the losses of separately powering the rotor coils. 

Solid state batteries

Schaeffler is now about three years into the solid-state journey. 

Today’s lithium-ion batteries have allowed us millions of electric cars on the road, but the industry is still battling with several issues. There’s constant news about battery fires, this ship is still waiting off the Alaskan Coast after a thermal event by batteries onboard. Lithium-ion batteries are much lighter than the old nickel-cadmium cells, but they’re still very heavy, causing other problems in heavy-duty trucks such as increased tire wear and tear. 

These, and many other hurdles need to be solved before we can go 100% electric. 

Schaeffler sees the potential for solid-state to alleviate many of today’s challenges, and our company is uniquely positioned due to our long history of high-tech coatings. We have experience in everything from corrosion protection and wear reduction, all the way up to manufacturing bimetal plates for fuel cells or electrolyzers, for example. Fortunately for us, this coating expertise is very useful in solid-state battery production.  

Current state:

Currently, we’re at lab scale producing small pouch cells, and we’ve had very encouraging results so far. We’re making cells around 2 by 5 centimeters (full-size EV packs are around 100 by 300 millimeters). 

Schaeffler developed specialized fixtures so we can measure the voltage not only at the anode and cathode but also at the electrolyte, giving us insights into both our anode and cathode recipes and what influences those have on the cell. 

The next stage is to develop our pouch technology. This is design-critical because, with solid-state batteries, you don’t have the liquid electrolyte; you need to load the anode and cathode against the solid electrolyte. Our team is excellent in structural engineering, which gives us another big advantage. 

Some of the questions we’re trying to answer are: how do you compress that pouch cell? How do you keep it alive? How can you alter the chemistry to reduce the pressure that’s needed? When you’re in a full-sized pack, you need a less massive structure to keep it all compressed together, these are just some of the things that go into this very complicated development process. 

It’s not anything that will be in production tomorrow, we’re thinking around three to five years, probably, and there’s a chance that we don’t even produce the entire cells, we are still working on the recipe to decide if we make cells, license anode technology, partner with other manufacturers, etc. 

Special thanks to Jeff Hemphill for the interview!