How the fuel-cell cars compare

When we drove the Honda FCX and the GM Sequel fuel-cell prototype vehicles, we found that the Honda is much better finished and much more like a traditional car. (Read our complete first drive of the Honda FCX sedan.) It feels like a very nice Honda Accord, with an electric whine taking the place of the buzzing hum of a gasoline engine.

The Sequel is more futuristic and less fully developed. It is a concept car designed to demonstrate both fuel cell technology and General Motors's futuristic "skateboard" chassis architecture. The "skateboard" architecture uses a separate body and mechanical running chassis (almost like frame-based cars from the 1930s), with only an electrical linkage between the actual mechanical systems, like steering and braking, and controls, like the steering wheel and brake pedal. GM is investing a great deal in this system because it can revolutionize car design and make it much cheaper to build a wide variety of body styles and power systems such as gas engines, fuel cells, and batteries, plus ethanol or diesel-fueld powerplants.

Driving differences

With the FCX, CR Senior Engineer Gabe Shenhar and I got in, turned the key, and drove around the quick mile-long parking-lot loop at high speeds by ourselves.

The Sequel, on the other hand, came with its own riding-mechanic: a GM employee in the back seat armed with a laptop computer to monitor everything from the fuel cell to the steering and brakes. After creeping a few feet, one of the brakes signaled an error and I had to turn the car off to reboot it – a process that took a minute or two. It is relevant to note that Honda plans to put the FCX into production next year, while the Sequel will remain a prototype. (The next generation fuel-cell car from GM will be based on the Chevrolet Equinox, and will be available to fleets starting in 2010.) While the Sequel had just traveled 300 miles at Interstate speeds that GM estimated averaged 65 mph, we were only allowed to drive on a low-speed loop, because the cars had little fuel left after the long trip.

Both cars had powerful low-speed acceleration and the Honda had adequate acceleration at highway speeds.

In the fuel cell itself, the Honda also seemed better developed. One of the engineering challenges of fuel cells is the ability to run them in very cold temperatures. Honda said its fuel cell could operate at any temperature above -4 degrees Fahrenheit. GM said its fuel cell could operate only at temperatures above 41 degrees Fahrenheit.

Honda claims a range of 271 miles for its FCX, but privately one Honda spokesman admitted that was a target range and that the company is stretching to achieve that. Here, GM has a potential advantage with the Sequel's estimated 300-mile range.

The reason for this difference exemplifies the companies' different approaches to fuel-cell cars: The FCX uses a very large hydrogen storage tank that takes up a lot of trunk space. It stores about 4 kilograms of hydrogen at 5,000 psi pressure, or the equivalent of about four gallons of gas. Honda uses this pressure because it is the pressure at which commercial hydrogen facilities today store and dispense the gas, even though it requires a large tank for a relatively limited range.

The Sequel stores compressed hydrogen at 10,000 psi in three tanks within the skateboard chassis, which takes up no cargo or passenger space and provides its longer range. But the "clean" hydrogen it bought from a Niagara Falls plant for the demonstration trip had to be compressed to twice its normal pressure to achieve that high psi level. And that took extra energy, provided by an electric compressor running on power from a local coal-fired powerplant. So, the well-intentioned trip was not entirely pollution-free, and thereby revealing the challenges in creating a truly clean alternative powertrain.

The next blog in the series will further explore the Honda fuel-cell technology.

--Eric Evarts