(February 22, 2010) The latest concept vehicle from Mercedes-Benz will debut next week at the Geneva Motor Show with the capability to support either plug-in hybrid or hydrogen fuel cell powertrains. The F800 Style concept is a preview of the next generation CLS luxury sedan with its sleek coupe-like greenhouse profile. Under the new skin is a platform architecture that supports multiple powertrain configurations.

The plug-in hybrid drive system is based on the architecture of the mild hybrid system found in the current S400 hybrid. Unlike the two-mode hybrid system used in the ML450 hybrid, the disk shaped electric motor is sandwiched between the engine flywheel and seven speed automatic transmission.

The production S400 uses a 15 kW electric motor/generator which is insufficient to drive the big luxury sedan on electricity alone. The motor in the new concept is increased in size to 80 kW allowing the car to be propelled electrically at speeds of up to 75 mph.

A previous S500 plug-in hybrid concept used a similar architecture with a 44 kW version of the motor. Both the S500 and F800 feature a clutch between the flywheel and motor allowing the internal combustion powerplant to be completely decoupled for maximum efficiency.

Like the S400 the F800 concept uses a lithium ion battery pack. However, the mild hybrid production car has a compact unit mounted under-hood in the same location as the conventional lead acid starter battery. The plug-in concept has a larger lithium ion pack mounted under the rear seat. Mercedes-Benz lists the capacity of the battery pack at greater than 10 kWh and claims the electric driving range on a single charge is approximately 18.6 miles.

As a hybrid the F800 still has an internal combustion engine, in this case a 3.5-liter gasoline direct injected V6. The combined output of the gasoline and electric power-plants is 409 hp is enough to accelerate the concept to 100 km/h in just 4.8 seconds. Meanwhile Mercedes-Benz claims that the F800 gets a combined 2.9 L/100 km or 81.1 mpg (US) and CO2 emissions of 68 g/km.

It's not known at this time precisely how that efficiency figure was determined. The consumption figures for plug-in hybrid vehicles are highly dependent on the duty cycle and how far beyond the battery range the vehicle is driven. The results will be vastly different if this vehicle is driven 20 miles or 100 miles without a recharge.

The second powertrain that is available for the F800 is a pure electric hydrogen fuel cell system. The emissions free drive system consists of a 100 kW electric motor with 214 pound-feet of torque. The F800 uses the same fuel cell stack installed in the latest generation B-Class F-Cell as well as the new Citaro bus (the bus uses two stacks). Like other fuel cell vehicles, a lithium ion battery is used to store electrical energy from regenerative braking.

 
Four hydrogen storage tanks reside in the center tunnel with a total capacity of 5.2 kg at 700 BAR pressure. Mercedes claims that this layout provides a driving range of over 370 miles. The hermitically sealed tanks prevent any leakage of the compressed hydrogen gas if the car is left sitting for an extended period.

In order to help the driver make the best use of the electric drive capabilities of the F800, Mercedes-Benz has implemented a range on map function on the navigation screen. A circular electric driving range is displayed on the map to show how far the vehicle can go before having to be charged, filled or run on the engine. If charging stations could also be displayed on the map, a driver could make their way to the nearest charge point to plug in, thus minimizing emissions.