The Chevrolet Sequel is an all-wheel-drive 5-seater crossover vehicle that runs solely on hydrogen, which is converted into electricity via a fuel cell to drive its three electric motors. It has a range of 300 miles per tank and a top speed of 90mph. We took it for a drive in the Californian desert this week, and found that it drove and handled much like a regular car.
While it might look like a regular car, the Sequel is anything but: aside from the fact that it runs on hydrogen, the Sequel relies on electronic--or "by-wire"--controls for all throttle, steering, and braking systems. The car also features four-wheel steering and braking. The Sequel's propulsion system means that it is significantly heavier (4774Kg) than a similarly sized crossover vehicle, although it does meet all federal safety standards.
Chris Borroni-Bird, the engineer who directed the Sequel project, talked us through the design and operation of GM's fourth-generation hydrogen fuel cell car. He said that the skateboard design enabled the car's components to be packed under the body "like a suitcase." He said that when designing the Sequel, his team wanted to make sure that it didn't feel like an advanced technology vehicle.
Like GM's Hy-wire and AUTOnomy concept cars, the Sequel is based on a "skateboard" design, with all propulsion systems, steering, braking and chassis components packed into the car's underbelly. GM says that this allows greater freedom for the car's interior and exterior design.
GM showed off its previous hydrogen fuel-cell vehicle at the launch of the Sequel. Pictures of the ill-fated EV1 electric car were also on show to add to the GM alternative-fuel-source-vehicle family atmosphere.
As with all of the Sequel's systems, the car's four-wheel steering is controlled entirely by electronic inputs using a 42-volt Flexray communication infrastructure. Road feel and steering feedback is replicated for the driver using a motor, while a brake provides artificial end stops. If both the primary and redundant steering systems fail, the car reverts to a mechanical steering backup.
The Sequel is powered by a 65kW lithium-ion high-power battery pack, which derives its charge from a fuel-cell module located under the driver's feet. Unlike Ford, which outsources the development of its hydrogen fuel-cell stacks to Ballard, a third party, GM designs and builds its own fuel cells in-house.
In contrast to other electric-powered vehicles, the Sequel uses two 25kW wheel-hub motors to drive its rear wheels, while a 3-phase asynchronous 65kW axle motor drives the front two wheels. Putting its motors in the wheels makes for instant torque and lowers the car's center of gravity. Together, the three motors generate a total of 2,920 lb-ft of torque--enough to propel the car from 0 to 60mph in less than 10 seconds.
The Sequel stores 8Kg of hydrogen, pressurized to 10,000psi in three carbon composite high-pressure tanks. According to GM engineers, the car takes about 8 minutes to fill from empty using a standard hydrogen pumping station. Filling the car using a mobile unit takes more than an hour.
One of the challenges with hydrogen fuel-cell cars is the high ambient temperature created by the chemical conversion of hydrogen into electric power and water vapor. In place of exhaust pipes, the Sequel has two air intakes at the rear, which suck in air to cool the hydrogen fuel-cell stack.
As it has no internal combustion engine, the Sequel's uses the space under the hood to house its air-conditioning unit.
From the driver's seat, the Sequel feels like any other car, with conventional gas and brake pedals in their usual configurations. While cabin technology is not a primary focus of the Sequel, the car does feature an i-Drive-like controller in the center console, which can be used to control air-conditioning, audio, and navigation. However, our test car--one of only two in existence--didn't have navigation or radio reception hooked up.
This week, Bob Lutz, GM's head of product development, said that the company now has the capacity to fund full production versions of its hydrogen fuel-cell vehicles.