Mercedes-Benz will be presenting the first "three-liter car" in the premium segment — the Mercedes-Benz S500 Plug-in Hybrid Concept — at the 63rd IAA in Frankfurt. Not long after the successful market launch of the Mercedes-Benz S400 Hybrid, currently the most fuel-efficient luxury-segment sedan with a gasoline engine. The technology vehicle will display the future of Mercedes-Benz' modular set of Hybrid systems. The Mercedes-Benz S500 Plug-in Hybrid Concept can drive for up to 18 miles solely on electric drive and therefore without producing any local emissions. The efficient drive system combined with the CO2 bonus for the battery-electric driving mode enables the vehicle to achieve a certified consumption of only 3.2 litres of gasoline per 100 kilometers. With CO2 emissions of only 74 grams per kilometre in the NEDC (New European Driving Cycle), the experimental vehicle developed in Sindelfingen demonstrates the long-term viability of future Mercedes-Benz S-Class generations. The outstanding values are made possible by the combination of a plug-in Hybrid with the efficiency-boosting BlueEFFICIENCY measures. At the same time, the Mercedes-Benz S500 Plug-in Hybrid Concept has all of the strengths that are typical of the S Class: renowned comfort, outstanding safety and superior performance. The drive system in the concept car consists of three main components: a powerful V6 gasoline engine with a next-generation direct injection system, a 44 kW/60 hp Hybrid module and a lithium-ion battery with more than 10 kWh of storage capacity that can be recharged at charging stations. The Mercedes-Benz S500 Plug-in Hybrid Concept accelerates from 0 to 60 mph in 5.4 seconds.
Mercedes-Benz S500 Plug-in Hybrid Concept (2009)


"The Mercedes-Benz S500 Plug-in Hybrid Concept is a new milestone on our path toward zero-emission mobility," says Dr. Dieter Zetsche, Chairman of Daimler AG and Head of Mercedes-Benz Cars. "It is a luxurious and safe S Class that offers superior driving performance while at the same time consuming less fuel than current compacts. All of this shows that our top models will also be able to combine automotive fascination with responsibility for the environment."

"Although it will take some time before this model can go into series production, our engineers will be working full steam to carry out the necessary integration measures and ensure that all components can meet the tough everyday demands required of a luxury long-distance sedan," says Dr. Thomas Weber, member of the Board of Management of Daimler AG with responsibility for Group Research and Mercedes-Benz Cars Development. "We've already got all the key technology we need for such a dream car, which is why I see it being included in the next gen-eration of the S Class. The important thing now is that our development work be accompanied by the establishment of a full-coverage infrastructure that will allow the potential of this innovative drive system to be fully exploited."

The electrical drive components of the Mercedes-Benz S500 Plug-in Hybrid Concept demonstrate the versatility of Mercedes-Benz' intelligently organized set of Hybrid systems, which has a widely scalable range of performance. The Hybrid module's design does not differ much from the compact, disc-shaped 15-kW electric motor of the S400 Hybrid, even though it is three times as powerful. As a result, the Hybrid module can be elegantly incorporated into the housing of the 7G-TRONIC seven-speed automatic transmission, allowing this model variant as well as the S400 Hybrid to retain the S Class' spacious interior. Future model generations will orient themselves on this system architecture.

Whereas the extremely compact lithium-ion battery in the S400 Hybrid (0.9 kWh) can be housed in the vehicle's engine compartment, the significantly higher-performing lithium-ion unit in the Mercedes-Benz S500 Plug-in Hybrid Concept (over 10 kWh) requires more installation space. The battery is located behind the rear seats in the trunk. The lithium-ion battery's location above the rear axle provides crucial benefits, since it ensures that the vehicle has a balanced weight distribution and that the gasoline tank remains adequate for long-distance cruising. In addition, the protected position of the tank ensures it is as safe as possible during crashes.

Additional clutch decouples the Hybrid module and combustion engine

In accordance with the modular concept, the powertrain design for the Mercedes-Benz S500 Plug-in Hybrid Concept is basically the same as that for the S400 Hybrid.

One system-specific attribute is the presence of an additional clutch integrated between the combustion engine and the electric motor. This device decouples the two components in the pure electric drive mode, thereby ensuring the highest level of efficiency in the latter. Moreover, because it is fully integrated into the vehicle's converter housing, the clutch does not take up any additional space.

Electrical outlet as a filling station: Powerful plug-in battery

Another key difference between the Mercedes-Benz S500 Plug-in Hybrid and conventional hy-brids involves the plug-in battery, which can be charged at charging stations, thereby enabling the Mercedes-Benz S500 Plug-in Hybrid to travel up to 18 miles on electric power. The rapid charge cycle takes less than 60 minutes with a charging capac-tiy of 20 kW. A standard charge cycle at a conventional household socket with 3.3 kW takes about four-and-a-half hours to recharge a completely discharged battery.

The model is also equipped with a compact onboard charger: Housed behind the side trunk wall, this unit controls the recharging process and is protected against short circuits, voltage reversal, and voltage surges. The charging system also pro-tects the battery by monitoring voltage, the charging level and charging time. The total weight of the electrical components in the current experimental vehicle is 474 pounds, whereby the lithium-ion battery weighs approximately 286 pounds. That's much less than a conventional NiMH battery with the same capacity, as the weight of such batteries ranges from 397 - 441 lbs.

The vehicle's Hybrid module also provides additional energy when the car is in motion through regenerative braking — the recovery of energy when braking. Here, the clutch enhances efficiency as well, as it enables complete energy regen-eration without engine drag losses.

Range of up to 18 miles with all-electric driving

The high-performance battery and the 44 kW/60 hp Hybrid module enable the vehicle to drive up to 18 miles purely on electricity. That is completely sufficient for many trips within cities, where the Mercedes-Benz S500 Plug-in Hybrid Concept is quick and very comfortable without producing any local emissions. The gasoline engine automatically adds its power to that of the electric motor when travelling at high speeds or driving up steep inclines. Before closing the clutch in such cases, the vehicle electronics synchronises the engine speed with the Hybrid module's rotational speed so that the engine is activated extremely smoothly without the driver noticing.

What's more, the Hybrid module's sophisticated interplay with the combustion engine enables numerous additional functions that positively impact fuel consumption, emissions and vehicle agility. Like the system employed in the S400 Hybrid, the Hybrid module in the Mercedes-Benz S500 Plug-in Hybrid Concept also comes with the ECO start/stop function. This feature also enhances safety and driving pleasure because of its boost effect, which has the electric motor providing powerful support to the combustion engine during the high-consumption acceleration phase. This system has already proved its practical viability in a slightly different configuration in the Mercedes-Benz Sprinter.

Extensive electronic safety and control components

The lithium-ion battery not only serves as an energy storage device for the elec-tric motor in the Mercedes-Benz S500 Plug-in Hybrid; it is also linked via a DC-DC converter to the 12-volt on-board network, which provides power to standard consumers such as the headlamps and various comfort devices. To ensure a consistently high level of electrical efficiency, the voltage transformers are water-cooled via an additional low-temperature circuit.

Special power electronics are required for operating the three-phase AC electric motor in the high-voltage direct current grid, and the inverter for this task is hou-sed in the engine compartment. Because the power electronics system itself is heated by the electric current thus created, it too is integrated into the low-temperature cooling circuit. Mercedes-Benz employs standardized components for the power electronics system as well, enabling them to be efficiently com-bined with different electric motors and battery types across all model series.

On the road to plug-in Hybrids: Diesel-Hybrid concepts

An important milestone on the road to plug-in Hybrids is the recently unveiled Vision E300 BlueTEC Hybrid diesel Hybrid. Like the S400 Hybrid and the Mercedes-Benz S500 Plug-in Hybrid Concept, it is based on the Mercedes-Benz modular Hybrid concept. This near-series vehicle study combines a new 2.2-liter, four-cylinder diesel engine with the 15 kW/20 hp Hybrid module that is also used in the S400 Hybrid, but which here also enables pure electric driving. This drive system configuration enables the Vision E300 BlueTEC Hybrid to travel over 60 miles on only 1 gallon of fuel (preliminary value). This corresponds to CO2 emissions of 119 grams per kilometre with an output of 165 kW/224 hp and superior torque of 580 - 600 newtonmetres (combined in both cases), more or less the same performance as today's six-cylinder diesel engines. Exhaust gas treatment is handled by the combination of an oxidizing catalytic converter, a diesel particulate filter and BlueTEC with AdBlue® injection. The Vision E300 BlueTEC Hybrid thus also has the potential to meet the world's most stringent emission standards.

Mercedes-Benz S500 Plug-in Hybrid Concept - Technical Data
Combustion engine (gasoline)
No. of cylinders/arrangement: V-6, 4 valves per cylinder
Displacement: 3.5 l
Hybrid module
Type: Permanently excited synchronous machine
Rated output: approx. 44 kW/60 PS
Rated torque: 184 lb-ft
Performance and fuel consumption
Acceleration 0-60 mph: 5.4 s
Top speed: 155 mph (250 km/h)
Fuel consumption: 3.2 l/100 km (combined)
CO2 emissions: 74 g/km (combined)