Mercedes-Benz Cars also set the tone for progress at the IAA with the ?S 400 HYBRID. The vehicle, which will initially be launched in Europe in mid-2009, boasts three hybrid functions: an automatic start/stop mechanism for fuel savings and comfort, an energy recovery system that also lowers fuel consumption, and a booster function that leads to outstanding levels of handling.

The S 400 HYBRID has a V6 gasoline engine with an output of 205 kW/279 hp that is linked to a hybrid module delivering maximum torque of 160 Nm and an output of 15 kW/20 hp. The combined output of 220 kW/299 hp and maximum torque of 375 Nm enable the vehicle to accelerate from zero to 100 kilometers per hour in just 7.3 seconds on its way to an electronically limited top speed of 250 kilometers per hour.

“In the current S-Class, we’ve succeeded in integrating all the relevant hybrid components into the front of the vehicle,” says project manager Oliver Vollrath from the Vehicle Development department at the Mercedes Technology Center (MTC) Sindelfingen, Germany. “And that means everything from the electric motor to the high-voltage storage battery.” Along with this “packaging,” the engineers focused mostly on the development of new components for the hybrid drive. One result is a ring-shaped electric motor only a few centimeters thick that is mounted directly on the crankshaft between the S 400 HYBRID’s engine block and 7G-TRONIC automatic transmission. Technically speaking, this unit belongs to the family of “external-rotor motors” and achieves its high output of 15 kW thanks to additional magnets in its rotor. When used as a generator, it delivers up to 20 kW.

Lithium-ion battery

Depending on the situation, the electric motor can serve either as a generator for producing electricity or as a starter motor that can also provide additional propulsion power. The latter offers big benefits — particularly in heavy city traffic — because it enables the vehicle to use a fuel-saving automatic stop-and-go system. In addition, the electric motor supplies its maximum torque during initial acceleration.

The electric motor is controlled by a sophisticated electronic system linked to it by a conductor bar. A major technological highlight in the S 400 HYBRID is a high-voltage battery that stores energy for the electric motor. This lithium-ion battery is cooled by the vehicle’s air-conditioning system, thereby ensuring reliable operation even at high temperatures. Because the powerful 120-volt battery is no larger than a conventional 12-volt car battery, it can be mounted in exactly the same place under the hood.

Auxiliary electrical devices

The 12-volt onboard electrical network is linked to the 120-volt hybrid system by a DC/DC converter that can transform electricity up or down. This leads to two benefits: the 12-volt onboard network can be supplied by the high-voltage battery when the electric motor is off, and the 120-volt battery can be recharged using a normal 12-volt charging device.

Another hybrid element packed into the engine compartment by Mercedes engineers is an electric vacuum pump, which creates the vacuum otherwise generated by the combustion engine for the brake booster. There’s also a special electric-hydraulic device for the power steering. The air conditioning system is electric as well, which means it can be operated even when the engine is off. The 7G-TRONIC automatic transmission is equipped with an electric oil pump that compensates for the loss of oil pressure when the engine is turned off. A further hybrid ace in the hole in the S 400 is a brake energy recovery system. Here, the electric motor is driven by the rear axle during braking. In other words, the motor acts as a generator and the current thus generated is stored in the high-voltage battery.

Economical Luxury Class: S 400 Hybrid
The S 400 HYBRID boasts a start/stop mechanism, brake energy recovery system, booster effect, and powerful lithium-ion battery.
Engine:
Gasoline engine	V6
Rated output	205 kW / 279 hp
Max. torque	338 Nm
Hybrid module:
Type	Disk-shaped electric motor
Max. torque	160 Nm
Overall drive system:
Combined max. torque	375 Nm
Overall fuel consumption:
Consumption (NEDC)	7.9 l/100 km
CO2emissions	190 g/km