Southern California fuel-cell devotees rejoice! You are about to get a second chance at blazing the trail toward long-range, quick-recharge, electric motoring that leaves nothing but pristine steam in your wake. So stop coveting thy neighbor’s Honda FCX Clarity and commence groveling to your Mercedes-Benz dealer in hopes of getting a crack at leasing one of 60 B-Class F-CELLs that will become available in SoCal late in the spring of 2010.
The B-Class, for those who don’t follow the tri-star’s home-market offerings, is a larger, roomier riff on the A-Class compact, both of which were developed with a sandwich floor construction designed to accommodate fuel tanks, exhaust systems, and even some of the combustion drivetrain beneath a slightly elevated floor. The design works well enough for the mass-market combustion vehicles, but it seems optimized for fuel-cell duty. The entire 80-kilowatt fuel cell, 1.4-kilowatt-hour lithium-ion battery pack, and three 10,500 psi hydrogen tanks fit completely out of sight without impinging on the passenger or cargo space of the petro-powered variant. Those tanks refill in three minutes and hold 3.7 kg (8.2 pounds) of hydrogen, good for a claimed 285 miles of driving on the U.S. EPA combined cycle. Mercedes claims that makes this the longest-range electric-powered production vehicle. That equates, engineers claim, to 85 miles per diesel fuel gallon equivalent on the EPA cycle. Impressive, given that the fuel-cell hardware adds 550 pounds to a B200 turbo with equal performance (9.6 seconds, 0-62 mph).
Mercedes counts this as its second-generation fuel cell, though in truth there has been more or less constant development and improvement since the original design filled the back of the 1997 Necar van. The F-cell’s proton-exchange membrane stack consists of 380 individual cells, into which compressed air is pumped at 36 psi from a screw-type compressor, which is also used to completely dry the fuel-cell stack after shutdown in cold weather, which allows cold starts in almost normal time from -13 degrees F and full functionality after a slightly longer wait from -40. A gauge on the dash indicates the fuel cell’s state of readiness, which transitioned from about 50 percent to full in some 20 seconds at 60 degrees F. During that time, the car can be driven — at least moved in and out of the driveway — using energy from the battery before full power becomes available.
Perhaps by way of foreshadowing the level of wealth that will be required to help pioneer fuel-cell motoring, Mercedes launched the B-Class with a drive in and around Monte Carlo, Monaco. My first impression was how polished and production ready this car feels in comparison with every previous fuel-cell mule I’ve tested. Gone were the howling compressor noise and shrill electric motor whine I’ve shouted at engineers about in the past. Yes, you can still hear the motor — at all speeds right down to a near stop, and you can hear the compressor if nobody speaks and the radio and fan are off. But by and large, it’s just a polished, accomplished, practical, roomy four-door hatchback. A large power-use gauge replaces the tach, indicating via needle when the driver is regenerating energy, driving economically, or hot-dogging. A central display screen shows the flow of power to and from the wheels, battery, and fuel cell. The fuel-cell image shows white dots (hydrogen ions) and green circles (oxygen molecules) flowing together with water drops coming out. Precious.
The car works like most hybrids, launching smoothly with energy from the battery and then delivering power directly from the fuel cell to the traction motor at speeds above 8-12 mph. The battery satisfies modest power needs when cruising at a constant speed or accelerating very lightly. The throttle has a “kickdown switch” at the bottom of its travel (even though the transmission is a single speed), which summons full power from the battery as well as the fuel cell, providing a noticeable 20-kW boost in acceleration. What little opportunity there was for cornering revealed steering that felt obviously electric in its effort and lack of feedback, and cornering behavior as flat as one would expect from a car with almost all its heavy parts stashed beneath your feet. The suspension is essentially unchanged from regular production B-Class cars except to cope with the added weight. My co-drivers and I sampled the peak torque and kickdown sensations liberally and checked out the 100-mph stability (solid as any Benz), all of which plunged the hydrogen fuel gauge from about 7/8 to 3/4 tank in 20 miles. We felt bad for a second, and then thought, hey, with only water coming out of the tailpipe, who cares how much hydrogen gets burned — especially if, as Mercedes-Benz alleges, the hydrogen currently being produced as a byproduct of chemical manufacture is sufficient to power 750,000 cars per year?
[source:MotorTrend]
