New Tech, Longer Range, and Lower Prices Keep Rivian in the Game

Less than three years after the impressive debut of the R1T pickup truck, Rivian has gutted its original design and replaced most of the important parts with better ones that simplify assembly, increase reliability, extend driving range, and reduce cost.

Industry gadfly Sandy Munro had pointed out areas in need of simplification in his Munro Live teardown videos, and many of the updated parts address those criticisms. Indeed, Rivian engineers said they are excited to hear Munro’s future assessment of the second-generation R1T and R1S SUV.

Enduro Motors

All Rivian R1 models now use the company’s in-house designed and manufactured Enduro motors that were introduced in the company’s Electric Delivery Vans and which debuted in lower-cost two-motor R1 vehicles last year. The original four-motor R1s used Bosch-supplied motors installed in Rivian-assembled drive units.

Compared to the original models, the motors for the second-generation R1s are staggered, with smaller motors on the front axle and bigger ones at the rear, according to Rivian’s Principal Drive Unit Engineer, Mason Verbridge. “They were a little bit more equally sized in the original execution,” he said.

Rivian's dual-motor drive unit (left), tri-motor (center) and quad-motor (right). DAN CARNEY

“We learned that we actually had more torque than we needed on the original, from an off-roading perspective. Even in the most extreme corner cases, we didn't end up using it. Then, in the rear, if we want to go quicker, that's where you want to put the torque to have that acceleration from a weight transfer standpoint. So amped up the rear [motor] in terms of performance, and then actually downsized the front.”

Related:Rivian Ushers in the Age of Electric Pickup Trucks With the Impressive R1T

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As a result, the motors are identical in design, but different in length, at 85 mm for the front motors and 110 mm for the rears. “And then also, unlike the previous quad-motor, we have differences in ratio, so it is 11.7:1 in the rear versus 9.0:1 in the front,” Verbridge added.

The rear motors have mechanical disconnects from the wheels, so when driving gently on the highway, the rear motors disconnect to reduce mechanical drag, extending driving range. In an abrupt passing situation, the rear motors instantly reconnect, providing the requested acceleration.

This dual-motor drive unit incorporates left and right motors. Unlike the original Bosch motors, the Rivian Enduro motors are oil cooled for better thermal management. RIVIAN

These second-generation models will be available configured with either two, three, or four of the Enduro motors. There is also a software-enabled Performance version of the two-motor model, for four different power levels: 553 hp and 610 lb.-ft., 665 hp and 823 lb.-ft., 850 hp and 1,103 lb.-ft., and 1025 hp and 1,198 lb.-ft.

Zero to 60 mph acceleration ranges from 4.5 seconds to less than 2.5 seconds. One Rivian engineer has achieved 2.47 seconds on a 0-60 mph run.

Related:Engineering Solutions by Design News Talks Rivian's Hydraulic Damping

Improved Battery Pack

The Samsung 21700-type cylindrical battery cells employed in the Large Pack and Max Pack battery packs are each now 53 amp-hours each instead of 50 amp-hours due to improvements to the chemistry.

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Combined with many other changes such as the wheel/tire combinations and the installation of a heat pump for climate control, these juicier batteries produce a maximum driving range of 420 miles in the R1T and 410 miles in the R1S. Large Pack range is 330 miles.

Rivian's pouch-style lithium-iron phosphate battery cell. DAN CARNEY

The Standard Pack uses the pouch-style lithium-iron phosphate batteries pioneered in Rivian’s Electric Delivery Van that the company builds for Amazon. “This is less energy-dense, so you pay a mass penalty for the same energy, or volume, or capacity, but it is cheaper,” explained Rivian’s Director of New Technologies, Max Koff.

The Samsung 21700 53G cell used in Rivian's Large Pack and Max Pack models. DAN CARNEY

“Also, because you're switching to a larger cell, you have less connections,” he said. “These are all placed in series, so you're essentially taking that simplification and efficiency from a cost perspective, and passing it on to the customer.”

A module containing the Samsung 21700 cylindrical cells. RIVIAN

These pouch cells are designed to be the same height as a stack of two cylindrical cells, so they fit into the same battery case. There are changes here, as Rivian has switched from aluminum extrusions to die castings for the case housing. This provides better dimensional accuracy of 0.1 mm, Koff said. “From a structural efficiency standpoint, it's much better,” he said. The change saves an impressive 150 lbs. in the R1 vehicles.

Related:Rivian Reveals Some Tech Details of its $45,000 Compact Models

Rivian's die-cast battery pack housing for second-generation R1 models. DAN CARNEY

Additionally, the design has been simplified and made easier to service. The first-generation batteries had two high-voltage distribution boxes and a battery management system. The new battery consolidates all of this into a single module. “This module now lives in a separate location that has an access port from below,” Koff pointed out. “In the past, to service those items, which is about an eight-hour job, it's now about a one-hour job to get to these components. So very helpful from a service perspective.”

Exploded view of Rivian's battery pack. RIVIAN

Zonal Electronics Architecture

Rivian has migrated the R1 models from a conventional electrical architecture to a zonal architecture while also consolidating its electronic control units. The result is the elimination of 1.6 miles of heavy (44 lbs.) copper wiring and the reduction in the number of ECUs from 17 to just seven, with corresponding reductions in the number of connections. That reduces assembly complexity and long-term reliability by reducing the opportunity for problems.

The layout of Rivian's West, South, and East zones in the second-generation R1 zonal architecture. RIVIAN

The vehicles’ infotainment, autonomy, vehicle access, and battery management system each have their own dedicated ECU, while all the rest of the vehicles’ functions are controlled by just three ECUs. These work within a zonal architecture that is divided into three zones, the East, West, and South zones.

“Let's give the example of our suspension system,” said Rivian’s Director of Electrical Systems, Kyle Lobo. “It goes to two controllers. In the rear it'll go to the south, and then the front, it'll go to the west, and we network between them to do our suspension,” he said. “We've analyzed the bandwidth latencies and made sure that we can still maintain great performance with the distributed system.”

Rivian's Gen 1 (left) versus Gen 2 (right) ECU count and location. RIVIAN

The resulting simplification of the system eliminated one wiring harness and removed 80 connections that had to be made on the assembly line previously. They also replaced traditional fuses in the system with silicon MOSFET virtual fuses. When these switch off an overloaded circuit, the repair technician can switch them back on digitally after diagnosing the source of the problem. The MOSFETs monitor circuit current and cut it off if the current gets too high, Lobo explained.

Preventing Problems

An increasingly common problem with EVs is the drain on their 12-volt battery which can leave them dead even while the high-voltage battery has plenty of charge. Rivian has addressed this by adding a miniature DC-DC converter that provides power to the 12-volt battery from the main high-voltage pack, ensuring that the constant drain on that battery by the vehicle’s many systems never leaves the vehicle unable to start.

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The benefits of these many improvements are obvious, and it hasn’t been long since Rivian introduced its vehicles, which could lead us to wonder why they didn’t do it this way from the beginning. The Rivian teams responsible for the vehicle’s many subsystems were in parallel sprints to deliver their systems as quickly as possible so Rivian could bring the vehicles to market, Lobo explained.

This parallel work required siloed systems with their own processors so that they could be developed and manufactured independently. Now, with the vehicle completed, the teams could coordinate to integrate functions of their systems, he said. “Now you're asking all these teams to live in the same house, share the same processor, allocate the same RAM, so that just takes a lot more resources and learnings from doing it the first time.”

Rivian Autonomy Platform

Amid all the simplification and consolidation, the second-gen Rivians also do add some things. The sensor suite and compute platform for its driver assistance systems combine to boost the vehicles’ capabilities far beyond that of the original models.

The dual Nvidia Drive Orin processors contribute to the new computer’s astounding 250 trillion operations per second. That’s ten times the speed of the computer in the first-generation vehicles. “For most customers, their R1 Gen 2 will be the most powerful computer that they own,” noted James Philbin, director of autonomy.

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In observance of the garbage in-garbage out axiom, Rivian engineers also upgraded the sensors supplying that computer with information about its surroundings.  Now there are eleven high-resolution cameras, including new 4K HDR units, providing 360-degree visibility. They can see three times farther than the previous system, which is as much as ten seconds ahead at highway speeds.

The high-dynamic range cameras provide better visibility in situations like driving into a tunnel, reported Philbin. The array includes a new narrow-field-of-view camera that looks forward (much like the new center camera in the Subaru Forester’s EyeSight system) for that added range. There is also a driver-facing camera installed in the rearview mirror that is designed primarily to detect driver fatigue and distraction when the vehicle is in Enhanced Highway Assist mode, planned to roll out later this year.

Rivian's second-generation compute platform, containing two Nvidia Drive Orin processors to produce 250 trillion operations per second. DAN CARNEY

The current SAE Level 2 driver assistance system, called Highway Assist, automatically steers, brakes, and accelerates the vehicle on select highways while the driver maintains hands on the steering wheel. More premium features are on the way via over-the-air updates. They include Lane Change on Command, available this summer, and Enhanced Highway Assist, coming later this year. Enhanced Highway Assist, with still more capability will also be available later in the year.

Radar Love

The cameras are augmented by a battery of five radars. They include a front imaging radar that detects objects as far as 1,000 feet away even in bad weather and dim light, and corner radars that support the surround-view camera system with their overlapping fields of view to track objects in all directions simultaneously.

While Tesla’s boss has been famously dismissive of the necessity for anything but cameras for driver assistance systems, Rivian recognizes that each kind of sensor has its own pros and cons. “Great perception needs multiple modality,” said Philbin. Camera images have no depth and collect no information about objects’ velocity, he pointed out. “We are leveraging the strengths and mitigating the weaknesses of our sensor data.”

With all of this sensor data and a powerful compute platform, the new system runs an AI that anticipates, plans, and reacts in real time. It uses many of the same architectural elements as the large language models we all know, called “Vision Transformers.” They are used to perceive and understand surroundings, predict the behavior of others, and prepare the vehicle for what might come next.

The system constantly learns from human drivers and enhances over time. Understanding the reality of what it will see those human drivers doing, Rivian put guardrails in place so that it doesn’t imitate rolled stop signs. “We want it to leverage the good parts of what it sees,” said Philbin.

Unreal Graphics

In the cabin, R1 occupants are treated to improvements in the infotainment system, which uses the Unreal Engine to create on-screen images that have a cell-shaded illustrated appearance in place of the first-generation vehicle’s more realistic images.

“Unreal Engine not only helped us create the appearance of the drive modes in a very agile and iterative way, but it also allowed us to make each mode more dynamic,” explained Eddy Reyes, a senior manager on Rivian’s Embedded Software Experiences team on the company’s blog. “For example, any mode can smoothly transition into another mode the driver chooses. And even when the mode settles, the vehicle and environment around it remain dynamic. The viewer will see clouds, grass, flowers, and trees moving. They can even touch the vehicle with two fingers and pivot it around, and the environment moves

with it in three dimensions,”

The illustrated style depicting a race track setting for Rivian Sport drive mode in second-generation vehicles. RIVIAN

The system adds native support for the Apple Music app, but Rivian continues to resist providing Apple CarPlay or Android Auto support because those applications displace the company’s own interface. That interface includes a solution for the frustration of having to go through menu layers for common functions such as the hatch release or front trunk release.

There still are no physical buttons for those, and Rivian still has not put virtual buttons for those functions on the top level of the menu. But they have added a pop-up window that includes those and other commonly used functions that appears automatically whenever the vehicle is in Park. The pop-up can also be summoned at any time by pressing the icon of the car at the top of the screen, or by swiping right from the left side of the screen.

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That is a fine metaphor for Rivian’s many improvements to its R1 vehicles, which should be enough to motivate more shoppers to swipe right on them when picking an electric pickup or SUV.