What is it?
The way some of us will be driving in 2020 - possibly. With 100 fuel cell prototypes and 2.8 million miles of testing, Mercedes is now putting the nearly finalised fuel cell drivetrain into 200 B-Classes, with the intention of completing a few more years of real-world testing with real-world drivers.
This Mercedes-Benz B-Class F-Cell is as close to a production car as any fuel-cell-powered prototype in existence. That’s because the company has the huge advantage of the A/B-Class ‘sandwich’ platform, which was first launched in 1998.
Between the two floors there is a considerable void, which swallows three cylindrical hydrogen tanks, the fuel cell stack and a small lithium ion battery. The electric motor that drives the front wheels is mounted in the car’s nose.
Since the first A-Class-based prototype appeared in 1999, Mercedes has managed to massively shrink down the size of the fuel cell, as well as improving power output by 30 per cent and reducing hydrogen consumption by another 30 per cent.
The fuel cell stack can now also operate at 25deg C below freezing and it will start up instantly at -15deg. Cold-weather operation proved a developmental hurdle.
The hydrogen is pumped into the car’s three carbonfibre-wound tanks at 700bar and each tank holds just under 4kg of fuel. Mercedes claims a range of 250 miles at a cost today of £32. The ability to mount these tanks under the floor of the B-Class is a boon for crash safety.
While the fuel cell generates a charge to drive the electric motor, there’s also a 35kWh lithium ion battery mounted under the boot floor. This is used to both store energy from brake regeneration and for ‘cold starts’ while the fuel cell is coming up to its operating temperature. The battery can also be used to power the car on short journeys and when manoeuvring at low speeds.
What's it like?
It’s nearly impossible to tell that the car is anything other than a stock model. The interior is unchanged, there’s no loss of boot space and the only exterior clue is the special refuelling interface hidden behind the filler flap.
In terms of ride and handling, the B-Class F-Cell feels remarkably like its conventional sister cars. That is, a little dated. It suffers from a pretty stiff-legged ride, crashing over poor surfaces rather too often and delivering quite a lot of noise to the cabin while doing it.
However, the electric motor offers pretty brisk progress and, on good roads, the lack of underfloor mechanical action is very noticeable by its absence.
The combination of torque and a single transmission ratio means acceleration is utterly seamless. At higher speeds the car delivers a rather odd sensation, a kind of very low-friction progress, which might be best described as ‘whizzing’. The brakes, however, need to be stronger and more progressive.