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How Rivian cooked up a new motor for its electric vehicles in Normal

Jul 30, 2023

There’s a lot you’re not supposed to notice about Rivian’s new dual-motor EVs. It’s still meant to feel like a rocket taking off when you smash the pedal, just like its older quad-motor sibling. And you’ve still got enough juice to drive up a rock wall or down to the grocery store.

One thing you’ll definitely notice is the price. And that’s the idea.

The cheapest dual-motor versions of Rivian’s electric pickup and SUV are $14,000 less than the cheapest quad-motor versions. That’s a price difference that could matter as Rivian’s attentions turn from early adopters to a more cost-conscious next generation of EV buyers.

“That’s really important for us. It allows us to start to offer a broader range of price points for our flagship R1 (pickup and SUV) product,” said Rivian founder and CEO RJ Scaringe.

WGLT recently spent the day at Rivian’s plant in Normal, where the company invited media to show off its new dual-motor drive unit. Those Enduro motors were already being used in Rivian’s commercial delivery vans and, as of this summer, are now available in its consumer R1S and R1Ts too. The motors are being built in a new 620,000-square-foot expansion on the southwest corner of the sprawling Rivian complex – now the size of over 20 Walmarts.

The media show-and-tell was also a chance for Rivian to reset the narrative about overall production, which is finally accelerating after a difficult 2022 in which the company was held back by global supply chain challenges. Rivian just recently increased its production estimate slightly for 2023, to 52,000 vehicles.

“It’s a chance to give you a little exposure to how different of a place we’re in, in terms of production and production ramp, than we were 12 or 18 months ago when we first started,” Scaringe said.

Scaringe said the launch of the Enduro motor is emblematic of Rivian as a whole – how a complex system can be designed to work harmoniously together. There are 8,000 Rivian workers in Normal today – certainly meeting the definition of a complex system.

When Rivian’s first EVs rolled off the assembly line in September 2021, they were all quad-motor models. That means there’s an independent motor for each wheel. That’s great for the kind of off-road driving that’s core to Rivian’s adventurous brand. But it’s arguably overkill for more traditional on-road driving. Quad-motors are also costlier, and there are literally more parts – not ideal for navigating a supply-chain crunch.

So Rivian’s team set out to design a new drive unit from scratch — also known as “clean sheet.”

“To really do that, we had to focus on the optimization around spatial, structural, functional, as well as the cost-efficiencies throughout the development phase,” said Henry Huang, Rivian's senior director for powertrain and thermal engineering.

This time, they got to design the three main components to work in harmony: the rotor, the stator, and the inverter. The core science behind an EV motor didn’t change: When an electric current flows through the stator, it creates a magnetic field that causes the rotor to spin and the vehicle to move. That power comes in through the inverter, which sits on top of the drive unit like a lid. And the whole thing had to fit in a space that was initially designed for a much larger quad-motor.

All along the way, they could make choices to give Rivian more supply-chain flexibility, lower costs, or improve performance.

Power semiconductors, for example, have been hard to get during a global supply-chain crisis. So the power module inside the dual-motor’s inverter can be made with either of two kinds of silicon semiconductors that Rivian staff call “mechanically identical.”

And more of the work is being done in-house, in that new addition on the plant, similar to the vertical integration behind the software and network architecture elsewhere in Rivian’s vehicles. For example, there are 240 current-conducting hairpins that are precisely laser-loaded into the stator, and those hairpins come in 13 unique configurations. Those are made in-house.

On performance, there’s another important change: Rivian is using oil, rather than water, to better cool the rotor and stator inside the drive unit.

“The result of that is the continuous power that we can sustain for one hour for this drive unit. It’s substantially higher,” said Silva Hiti, senior director of electric power conversion. “The ratio of continuous power to big power is 60% or higher for this drive unit.”

Rivian also has almost two years’ worth of real driving behavior from its customers to learn from. An internal simulation optimization tool goes through thousands of different combinations of how the motor’s components can be used — to find the best one to deliver the performance the driver wants while maximizing range.

“What it really allows us to do — by owning every aspect of the design, from the inverter to the motor to the gearbox, and the integration of all those — is the ability for us to capture all the requirements and the unique customer use cases that we expect our customers to see,” Huang said.

One example is what’s called dynamic disconnect. EVs that are cruising along on a highway or don’t need to do any off-roading can disconnect, or turn off, the motor on their rear axle to preserve range. On Rivian’s quad-motor models, drivers would have to do this manually by choosing “Conserve” mode. But on the dual-motor models, this will happen automatically (while in “All-Purpose” mode).

That dynamic disconnect was on display during Rivian’s media day, when reporters got to drive the dual-motor and quad-motor models back-to-back on the company’s test track just east of the plant. For a layman, the difference wasn’t noticeable. (Out on the road, you can visually tell the difference between a dual-motor or quad-motor model by looking at the tires: If you see a yellow brake caliper, it’s quad. If it’s silver, it’s dual.)

Rivian just rolled out Enduro motors to its R1 production line. Tim Fallon, Rivian’s manufacturing chief in Normal, said the share of dual-motor R1s versus quad-motor is expected to increase “significantly,” over the 50% mark. But quad-motor will remain an option, he said.

“Having a dual-motor option really does allow us to open up EVs to a much broader audience, from a cost-competitiveness perspective. That’ll naturally drive some of the mix,” Fallon said.

Rivian is certainly talking more about cost-competitiveness today than it did, say, in 2018 when its EVs debuted with a luxury price tag at the LA Auto Show. In the years since, many automakers have announced their own new EV models, including pickups and SUVs that compete with Rivian. Ford’s electric F-150 starts at around $50,000. Tesla’s new Cybertruck is expected to start at around $50,000.

Rivian’s next product line — the R2 — will be cheaper still, reportedly in the $40,000 to $60,000 range. Those R2s will be made in Georgia at Rivian’s forthcoming plant starting in 2026.

The Enduro motor platform cooked up in Normal will serve as the “foundation” for the motors Rivian will use in the R2 platform.

“We expect the investment in our in-house drivetrain and power electronics capabilities to provide manufacturing and product advantages when launching our R2 platform,” the company said.