The B-Class F-CELL is the world’s first fuel cell electric vehicle to be built in an actual production environment. The test drive in a pre-production model is a real land-
mark moment – even if none of the first small produc-
tion batch of some 200 vehicles will be available for outright sale.
Apart from the unaccustomed silence when starting, everything else is just as you would expect in a Mercedes-Benz – or at least almost everything. In an otherwise familiar looking instrument panel, you’re soon struck by the absence of a rev counter, which has made way for a power meter instead. The quartet of instruments also includes an “F-CELL display”, which
is situated to the left of the speedometer and shows
the current operating status of the fuel cell system.
The electric motor revs up rapidly. That doesn’t alter the torque, though, which at every point in the rpm range remains at a constant 290 Newton meters. Having so much power on tap at all times takes a
little getting used to. The speedometer reaches the
100 km/h (62 mph) mark before you know it. Though the official 0 to 100 km/h (62 mph) sprint time is 11 seconds, it seems much less than that. The reason
is the linear acceleration. The car just keeps pressing forwards, with the rpm and power increasing in a steady stream. There is no interruption of the power flow for gear changes because the vast usable rpm range makes a multi-speed transmission unnecessary.
Its source is the electric compressor under the hood, whose job is to pump air into the fuel cell stack at a pressure of up to
1.8 bar, depending on accelerator position. The fuel cell stack, which consists of a large number of individual fuel cells stacked into one unit, is located in the sandwich floor beneath us, somewhere under the front seats. In this stack, the centrepiece of the B-Class F-CELL, the hydrogen combines with atmospheric oxygen to generate exactly the required amount of electrical energy (see panel), in line with the driver’s throttle commands. On one tankful – just under four kilograms (9 lbs) of hydrogen - the B-Class
F-CELL provides around 400 kilometres (250 miles)
of locally zero-emission driving.
The 35 kilowatt compact high-voltage battery responsible for the power boost requires no lengthy recharging plugged into the electric mains. Instead,
it is charged by the electric motor, which acts as a generator whenever the vehicle is coasting. The mo-
ment the driver eases off the accelerator, the power meter needle drops below zero, into the zone marked “Charge”, where the scale changes to a broken green line. This indicates that the battery, located under the rear seat bench, is now receiving charge. At the same time the numerical percentage displayed on the digital charge indicator increases, climbing even more quickly if the driver brakes. Up to 1.4 kWh of energy can be recuperated in this way and stored in the battery.
A separate cooling circuit for the lithium-ion battery keeps it at the right operating temperature at all times.
The next red traffic light and the ECO start/stop function switches the fuel cell system to standby, to conserve hydrogen. My foot goes back on the accelerator and the F-Cell purrs quietly on its way, without missing a beat. The power is initially supplied by the lithium-ion battery. Then from about 10 km/h (6 mph), the fuel cell is engaged as well.