General Motors’ Ultium platform has been in the news lately, so let’s dive deeper into exactly what this “platform” consists of. Boiled down, it’s a shared modular battery system powering a family of related motor/drive units under the watchful eye and rigorous control of an Ultifi software operating system running on GM’s latest Vehicle Intelligence Platform electrical architecture.
Ultium is not a “skateboard,” per se, as the vehicles it’s scheduled to underpin will use vastly different suspensions and frames tailored to their very different use cases. But what Ultium really is (listen up if you’re a shareholder) is GM’s roadmap to profitably electrifying its fleet by sharing as much of the pricey hardware as possible: the battery cells and monitoring system, the essential motor architecture, and the operating system. This makes the unseen electrified underpinnings scalable across the product portfolio. To wit: GM envisions some 19 battery and motor combinations. Contrast that with today’s staggering portfolio of 550 combustion-powertrain combinations.
The Ultium Battery
Cell Design: Using laptop-style cylindrical battery cells got Tesla into the market lickety-split, but the Ultium battery uses large (23.0-by-4.0-by-0.4-inch) pouch-type cells that package energy more densely than cylinders can. They weigh about 3 pounds each, hold 0.37 kWh of energy, can be arranged vertically or horizontally to suit space requirements, and are typically bundled into 24-cell modules. This design is also alleged to ease reuse and recycling.
Chemistry: Nickel-manganese-cobalt-aluminum chemistry reduces cobalt use by 70 percent relative to the Bolt EV’s NMC formula (both are lithium-ion). The aluminum also strengthens the electrodes and helps prevent lithium spike formation during fast charging, which can short-circuit a battery. This extends the useful battery life and reduces concerns about frequent DC fast charging. Second-gen lithium-metal batteries using a silicon-based electrolyte are being developed with SolidEnergy. They’re not quite solid-state, but they promise to double the NMCA batteries’ energy density at 60 percent the cost of the first-gen cells. And they’ll be backward-compatible so owners of first-gen Ultium products can upgrade to them, thanks to …
Wireless Battery Management: GM will be first to monitor battery cells wirelessly using the Bluetooth-like 2.4-GHz spectrum, reducing cost, weight, complexity, warranty problems, and space required to solder all those wired connections. It constantly monitors battery health, sharing info with the cloud to detect potential issues with certain battery batches, use cases, etc. Plus, it enables flash reprogramming when retrofitting newer battery chemistries or when repurposing a pack for its second life, perhaps in grid energy storage.
Capacity and Range: With each 24-cell Ultium battery module good for 8.9 kWh, expect to see six-module packs rated for 50-kWh usable capacity in the smallest, lightest vehicles, and the mighty 200-kWh (usable) pack topping the range in the GMC Hummer EV. GMC rates the latter at 329 miles (it exceeds the weight limit for EPA testing), but lighter vehicles with the biggest pack should exceed 400 miles, while the 100-kWh pack in the Cadillac Lyriq will deliver more than 300 miles.
Voltage and Charging: Most Ultium battery packs will operate at 400 volts, capable of DC fast charging at up to 250 kW. However, the Hummer EV’s two 400-volt packs can be virtually wired in series to emulate an 800-volt system during charging, which allows 350-kW chargers to add 100 miles in 10 minutes.
Cost: The smart design, NCMA chemistry, and vertically integrated manufacturing have dropped pack-level costs to near $100/kWh—one-tenth that of the 2010 Chevy Volt. This is crucial to making Ultium products profitable.
The Ultium Motor Family
At launch, three oil-cooled axial-flux motors (the traditional barrel-shaped ones, not the newer pancake style) are envisioned: two permanent-magnet machines good for up to 241 and 342 hp, and one AC induction-type good for 83 horses. The latter will be paired with one of the former to provide high-efficiency AWD, because it creates none of the electromagnetic drag when “coasting” that a permanent-magnet motor does. It appears the metal plates that get stacked together to form the stator are shared, with the more powerful motors getting more of them to become longer, their windings getting more “turns” and their rotors perhaps using more of the shared permanent magnets. All can be built using common tooling, and all motors will be unitized with a reduction drive and power inverter. Furthermore, GM will employ a control strategy that fine-tunes the input power every 10 milliseconds, boosting efficiency to near 97 percent and providing finer control during stability control interventions.
The first wave of Ultium products will package these three motors in five drive units: two of the largest motors ganged for rear-drive high performance, plus single-motor applications for each of the other three motors. (Both heavy- and light-duty applications are envisioned for the larger motor, which gets us to five units.) The chart below shows our best guess at what vehicles use which drive unit(s).
Ultifi Operating System
We have entered the age of the software-defined vehicle, and Ultium EVs will form the tip of GM’s spear in this regard. They will share a version of GM’s Vehicle Intelligence Platform electronic architecture introduced in 2019, which provides lightning-fast processing power and a robust, cybersecure cloud connection that enables over-the-air updates, vehicle-to-everything communication, and e-commerce—basically it makes vehicles behave like smartphones. The user interface will be via the Ultifi operating system. And because it’s Linux-based, it’s easy for third-party vendors to develop apps that—if approved by GM—can run on Ultifi.
Ultifi is designed to do two things for General Motors: increase customer loyalty and generate a new revenue stream. This will come from subscriptions to streaming content, concierge services, and selling permanent upgrades or renting temporary features over a vehicle’s useful lifetime (much longer than a combustion vehicle’s). Here are just a few envisioned for potential future rollout:
- Vehicle authorization using driver-facing camera and facial recognition software
- Automatic window/roof closing based on links to local weather forecasts
- Planetarium app using GPS location to indicate nearby star constellations on the infotainment screen(s)
- Gesundheit mode, which closes windows and activates air recirculation when pollen counts are high
- Monitoring of nearby traffic to learn of icy/slick spots, potholes, obstacles, etc.
- Enhanced powertrain and suspension settings for use during track days
Will Wall Street finally show GM some respect if it turns legitimate profits on its Ultium lineup of electric vehicles—and does so absent all the surplus EV credits that prop up Tesla’s balance sheets? Probably not, but a company can dream.
|Potential GM Ultium Motor Combinations|
|GM Ultium Family of Five Drive Units|
|Permanent Magnet||AC Induction|
|Vehicle Type||Hi-Perf Dual-Motor RWD||Hi-Perf FWD or RWD||Car/SUV RWD||Car/SUV FWD||Car/SUV Assist AWD||Output*|
|Extreme AWD Performance (GMC Hummer EV3)||X||X||–||–||–||1,000 hp, 1,200 lb-ft|
|AWD Performance/Work (Chevy Silverado EV, GMC Hummer EV2 & Sierra EV, Cadillac Celestiq)||X||X||–||–||–||510-664 hp, 780 lb-ft|
|RWD Work (Silverado EV Work Truck, Brightdrop vans)||–||X||–||–||–||340 hp, 325 lb-ft|
|RWD Luxe/Performance (Cadillac Lyriq & Symboliq)||–||–||X||–||–||340 hp, 325 lb-ft|
|Mid-Luxe AWD (Cadillac Lyriq & Symboliq, Buick Electra)||–||–||X||–||X||400 hp, 400 lb-ft|
|Mid-Luxe FWD (Buick Electra, Cadillac Optiq)||–||X||–||–||–||340 hp, 325 lb-ft|
|Mainstream AWD (Chevy Equinox, Blazer, entry Buick)||–||–||–||X||X||300 hp, 300 lb-ft|
|Mainstream FWD (Chevy Equinox, Bolt/Trailblazer)||–||–||–||X||–||241 hp, 230 lb-ft|
|*Estimates; peak output influenced by battery pairing, market segment, range goals, etc.|