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 saloon. 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 generation 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.

—Dr. Thomas Weber, member of the Board of Management of Daimler AG with responsibility for Group Research and Mercedes-Benz Cars Development

Hybrid system architecture of the Vision S 500 Plug-in HYBRID. Click to enlarge.

The electrical drive components of the Vision S 500 Plug-in HYBRID leverages Mercedes-Benz’ modular 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 S 400 HYBRID (earlier post), even though it is three times as powerful. As a result, the hybrid module can be incorporated into the housing of the 7G-TRONIC seven-speed automatic transmission, allowing this model variant as well as the S 400 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 S 400 HYBRID (0.9 kWh) can be housed in the vehicle’s engine compartment, the significantly higher-performing lithium-ion unit in the Vision S 500 Plug-in HYBRID (more than 10 kWh) requires more installation space, and is located behind the rear seats in the trunk. The pack’s location above the rear axle 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.

In accordance with the modular concept, the powertrain design for the Vision S 500 Plug-in HYBRID is basically the same as that for the S 400 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. The clutch enhances efficiency in regenerative braking as well, Mercedes says, as it enables complete energy regeneration without engine drag losses.

The high-performance battery and the 44 kW/60 hp hybrid module allow the vehicle to drive up to 30 kilometers purely on electricity. 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 synchronizes the engine speed with the hybrid module’s rotational speed so that the engine is activated smoothly without the driver noticing.

Like the system employed in the S 400 HYBRID, the hybrid module in the Vision S 500 Plug-in HYBRID 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.

The rapid charge cycle for the battery pack takes less than 60 minutes with a charging capacity 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 protects the battery by monitoring voltage, the charging level and charging time. The total weight of the electrical components in the current experimental vehicle is 215 kg, whereby the lithium-ion battery weighs approximately 130 kg. That’s much less than a conventional NiMH battery with the same capacity, as the weight of such batteries ranges from 180-200 kg.

The lithium-ion battery pack 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 housed 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 combined with different electric motors and battery types across all model series.

Vision E 300 BlueTEC HYBRID diesel hybrid. Mercedes-Benz is also highlighting the Vision E 300 BlueTEC HYBRID diesel hybrid. Like the S 400 HYBRID and the Vision S 500 Plug-in HYBRID, 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 S 400 HYBRID, but which in this application also enables pure electric driving. This drive system configuration enables the Vision E 300 BlueTEC HYBRID to travel 100 km on 4.5 liters of fuel (52 mpg US) (preliminary value). This corresponds to CO₂ emissions of 119 grams per kilometer with an output of 165 kW/224 hp and torque of 580 - 600 N·m (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.