Hydrogen has been on the minds of automakers for decades. Ever since GCJ editors experienced the hydrogen fuel cell Mercedes-Benz NECAR 2 (New Electric Car) on the streets of Berlin back in the mid-1990s, we’ve been believers that hydrogen could prove to be an important part of our zero-emission driving future. Over the years, concept, demonstration, and production hydrogen vehicles have been fielded by many automakers, from Chrysler, Ford and Nissan to Honda, Hyundai, and Toyota. One of the most notable was GM’s Sequel unveiled some 18 years ago, which followed in the footsteps of the automaker's Hi-wire hydrogen fuel cell concept Green Car Journal editors drove in 2003. The Sequel hydrogen fuel cell electric vehicle (FCEV) was decidedly ahead of its time with its skateboard platform, sandwich-style floor, steer-by-wire technology, lithium-ion batteries, and 10,000 psi fuel tanks. Read our take on GM’s groundbreaking Sequel, pulled from our archives just as it appeared in the magazine's Spring 2005 issue.
Excerpted from Spring 2005 Issue: Reality check time. When General Motors debuted the AUTOnomy and Hy-wire advanced technology concept cars at the Detroit and Paris auto shows three years ago, the vision of real-world hydrogen powered fuel cell cars still seemed very far away. Sequel brings those concepts home in a ‘do-able’ vehicle that is suddenly a lot less like science fiction and more like Main Street.
Hydrogen and Battery Power
Clearly, GM hasn’t lost sight of what seemed to many a lofty goal when the company announced its intention to design and validate a fuel cell propulsion system that could be manufactured and sold by 2010. While this date certainly won’t see mass commercialization of fuel cell vehicles at GM’s new car showrooms, the General is surely aiming at reaching that milestone with technology and vehicles that can be sold – at a cost far lower than today’s fuel cell vehicles – to fleets and others willing to pay the price to be early adopters.
Sequel utilizes GM’s concept of a separate, low-profile skateboard chassis that completely houses the fuel cell propulsion system. By decoupling the rolling chassis from the bodyshell and utilizing bi-wire control technology, Sequel’s architecture offers incredible flexibility for future models. That flexibility could provide a significant advantage as merging technologies bring fuel cells closer to the showroom.
Electric All-Wheel Drive FCEV
While a concept, Sequel aims to create fuel cell performance that meshes well with the kind of driving experience expected of modern vehicles. By utilizing three lightweight, high-pressure carbon composite hydrogen storage tanks, completely housed in the 11-inch thick chassis, Sequel boasts a driving range of about 300 miles. Combining electric motor front-wheel-drive with separate electric wheel hub motors at each rear wheel, Sequel is able to deliver all-wheel-drive traction and a noticeable increase in acceleration. According to GM, Sequel will scoot from 0-30 mph in three seconds and reach 60 mph in just over nine seconds. Top speed is said to be 90 mph.
That performance is made possible by a transversely mounted, three phase 80 horsepower (60 kW) electric motor at the front of the chassis and two 34 hp (25 kW) three phase electric wheel hub motors at the rear, which together deliver a total torque output of 2,506 lb-ft at the wheels.
Advanced Skateboard Chassis
GM’s skateboard chassis design holds several key advantages. Most significant is its inherent low center of gravity, which dramatically increases vehicle stability. With Sequel, GM engineers were able to deliver an ideal 50-50 weight distribution by placing the lithium-ion battery pack at the rear of the chassis, offsetting the motor mass up front. The hydrogen fuel cell stack is placed directly behind the front wheels beneath the driver/passenger compartment.
Midship, you’ll find the three high-pressure hydrogen storage tanks mounted in the sandwich style chassis, a location that provides the best protection from crash intrusion. These tanks have a service pressure of 10,000 psi, allowing them to carry much greater amounts of hydrogen than the 5,000 psi tanks used in the Hy-wire concept.
More Powerful Fuel Cell Stack
A high-power 65 kW lithium ion battery is employed for the power demands of launch and acceleration, but once up to speed, Sequel can cruise solely on the fuel cell. Auxiliary power generated by the fuel cell at cruising speed is combined with regenerative braking to top off the battery charge. Sequel utilizes aluminum substructures in the chassis design and extensive use of aluminum in the body panels and structure to minimize weight.
Sequel is also the showcase for GM’s next-generation fuel cell technology. The fuel cell stack delivers 25 percent more power than previous models. GM’s Fuel Cell Product Engineering facility in Honeoye Falls, New York, is working to simplify and better integrate the overall fuel cell stack and power module system design, which will ultimately drive down the cost of production.
Electronic Bi-Wire Control
”A fuel cell system is more efficient than an internal combustion engine, but its energy conversion is totally different and requires much more heat to be removed via the coolant,” points out Lothar Matejcek, project manager of GM Fuel Cell Activities in Mainz-Kastel, Germany. To extract the heat, Sequel uses multiple radiators with three large openings in the front of the vehicle and two additional openings in the rear. These openings are well integrated into the overall vehicle design and lend a very aggressive look to the body profile. This attention to cooling demands are said to allow the Sequel to operate at maximum power with full air conditioning even on 100 degree F days.
By-wire controls are utilized for all Sequel systems. Steering, braking, and acceleration are all free of mechanical and hydraulic control linkages. Pushing a pedal or turning the steering wheel sends an electronic signal from the vehicle controller to modulate power output, apply braking, and precisely control steering. Steer-by-wire on the Sequel processes steering inputs through a computer, actuating the front steering rack and two rear wheel steering actuators based on vehicle speed and driving conditions.
Advanced Interior Design
A major advantage to the separate low-profile chassis design is incredible flexibility in body and interior design, configuration, and packaging. Sequel is addressing a hot spot in the current vehicle market – the sport/luxury crossover SUV. In fact, GM compares Sequel’s size to the current Cadillac SRX crossover, with its measurements of 196.6 inches in overall length, 66.8 inches in height, and its 119.7 inch wheelbase.
Styling is contemporary, with a broad shouldered and aggressive stance enhanced by crisp lines that blend hard edges with flowing curves. The chassis design delivers wheels pushed to far corners of the body structure with little intrusion into the cabin area. GM stylists were careful not to push the design envelope too far with this concept, though, to deliver the notion that this is a real-world vehicle.
A Spacious Cabin
The five passenger interior is accessed through a pair of conventional doors up front with rear suicide-style door on either side of the cabin. There is no obstruction to the spacious interior with both doors open. Innovations inside are tempered by practicality. While this is a concept, the message is clear that Sequel is credible transport. One of the more striking design elements is the unique center glass sunroof that runs the length of the top. It is actually a series of individual glass panels that slide rearward and pivot up to provide a very airy cockpit.
The front passenger seat rotates 180 degrees to provide a conference-style seating configuration. Although it is drive-by-wire, all controls are familiar with a traditional steering wheel, accelerator, and brake pedals. The center console travels on a track that allows it to move from its normal location between the front seats to an aft position closer to rear seat passengers. Hinged at the front, the console’s lid pivots forward to reveal the Sequel’s audio, DVD, and navigation system. When in use as an entertainment center, the console is easily moved to the rear seat passengers for DVD movie viewing. The interior look and feel is contemporary and tasteful with metal and wood accents combined with a palette of plum, rice, and wasabi hue trim.
Sequel is the culmination of a global effort by General Motors to advance fuel cell vehicle design. Nearly 200 suppliers from around the world were sourced to fuse the latest technology into a vehicle that brings a clean, hydrogen fueled future a bit closer to home.