Vehicle: Vision S 500 Plug-in HYBRID
When: September 2009
Where: IAA International Motor Show, Frankfurt am Main
What: luxury class car with a consumption level of three litres per 100 kilometres, achieved through the use of a hybrid modular system
Drivetrain: 3.5-litre V6 internal combustion engine with next-generation direct injection, combined with a hybrid module (44 kW/60 hp) as well as a lithium-ion battery with a storage capacity of more than 10 kWh
Powerful hybrid module integrated in the housing of the 7G-TRONIC 7-speed automatic transmission
Additional clutch between internal combustion engine and hybrid module for even greater efficiency
Plug-in battery could be recharged at charging station and made it possible to drive up to 30 kilometres under electric power alone. In the rapid charge mode with 20 kW charging power the process took less than 60 minutes
Shortly after the successful market launch of the S 400 HYBRID model as the most economical luxury saloon with an Otto-cycle internal combustion engine, Mercedes-Benz presented the Vision S 500 Plug-in HYBRID at the 63rd. International Motor Show (IAA) in Frankfurt/Main in 2009, the first luxury-class model in the ‘three-litre per hundred km’ category. This technology carrier was developed on the basis of a 221 model series S-Class, and showed the future of the hybrid system modular design principle from Mercedes-Benz. It had the capacity to travel up to 30 km powered exclusively by electricity, thus creating no local emissions. Thanks to its efficient drive system and the carbon dioxide bonus for battery electric powered operation it achieved a certified consumption level of just 3.2 litres of petrol fuel per 100 kilometres. With carbon dioxide emissions of only 74 grams per kilometre in the NEDC (New European Driving Cycle), the experimental vehicle demonstrated the future-compatibility of coming S-Class generations. These exceptional levels were achieved thanks to the combination of a plug-in hybrid drive system with efficiency-enhancing BlueEFFICIENCY measures.
At the same time, the Vision S 500 plug-in HYBRID featured all the typical strong points of the Mercedes-Benz S-Class: top-level comfort, exceptional safety and effortlessly superior performance. The concept vehicle’s drive system consisted of three main components: a powerful V6 internal combustion engine featuring next-generation direct injection, a hybrid module delivering 44 kW (60 hp), and a lithium-ion battery with over 10 kWh storage capacity, which could be recharged at a charging station. The vehicle was able to accelerate to 100 km/h from a standstill in 5.5 seconds.
The electrical drive system components demonstrated the versatility of the Mercedes-Benz scaleable hybrid drive system modular principle. In its design, the hybrid module presented only minor differences from the 15 kW electric motor with which the S 400 HYBRID was equipped, although it was three times as powerful as the latter. For this reason it was possible to integrate it elegantly in the housing of the 7-speed 7G-TRONIC automatic transmission. This hybrid variant left the generous interior of the experimental vehicle intact, as did the S 400 HYBRID – an important guide for future model generations
Whereas the extremely compact lithium-ion battery of the S 400 HYBRID with a capacity of 0.9 kWh in fit easily in its engine compartment, the lithium-ion battery of the Vision S 500 Plug-in HYBRID, at 10 kWh considerably stronger, requires more space. The accumulator is therefore located in the boot behind the rear seats and above the rear axle. This installation location offers decisive benefits: the weight distribution in the vehicle is balanced and the petrol tank retains a volume compatible with an extended range. In addition the position offers the best possible protection in the event of a collision.
In consonance with the modular design concept, the drivetrain of the Vision S 500 Plug-in HYBRID was in principle designed exactly like that of the S 400 HYBRID. A feature specific to the system was the additional clutch integrated between the internal combustion engine and the electric motor. It decoupled the two assemblies when driving under electric power alone, so that the highest efficiency was guaranteed in electric mode. As it was possible to fully integrate it into the torque converter housing, the separating clutch did not need any additional installation space.
A further important difference from conventional hybrid vehicles was its plug-in battery, which could be recharged at charging stations. This enabled the Vision S 500 Plug-in HYBRID to be driven up to 30 kilometres under electric power alone. The rapid-charge mode with a charging capacity of 20 kW took less than 60 minutes. A standard recharge of a totally discharged battery at a conventional wall socket, 3.3 kW took around four and a half hours.
The compact on-board charger was located behind the lateral boot wall; it regulated the charging process and was protected against short circuit, polarity reversal and overvoltage. At the same time the charging system monitored the voltage, charge intensity and charging time for the protection of the battery. The total weight of the electric components in the experimental vehicle was 215 kilograms, towards which the lithium-ion battery contributed around 130 kilos, considerably less than a conventional nickel-metal-hydride battery of similar capacity, which would have weighed 180 to 200 kilograms.
The hybrid module refreshed the battery while driving, too: through the so-called recuperation process, the use of braking energy. In this context, the separating clutch also enhanced efficiency, as it enabled full recuperation of the kinetic energy without losses caused by engine drag.
The high-performance battery and the around 44 kW (60 hp) hybrid module enabled electricity-powered trips of up to 30 km, sufficient for most drives into town. And the Vision S 500 Plug-in HYBRID offered swift, very comfortable and locally emission free driving in this mode. At speed or on very steep climbs, the internal combustion engine kicked in automatically. Before closing the clutch, the vehicle electronics synchronised the rev speeds of internal combustion engine and hybrid module, so that switching-in proceeded absolutely jolt-free and unnoticeably. The sophisticated interplay with the internal combustion engine made numerous additional functions possible: this exerted a positive influence both on emissions and agility. Like the system in the S 400 HYBRID, the hybrid module in the Vision S 500 Plug-in HYBRID also featured an ECO start/stop function. It enhanced safety and motoring enjoyment by means of the so-called ‘boost’ effect with which the electric motor powerfully assisted the internal combustion engine in the high-consumption acceleration phase. In a slightly modified configuration, the system had already proven its day-to-day practicality in the Mercedes-Benz Sprinter.
The lithium-ion battery not only serves as energy storage for the electric motor, it is also connected via a DC-to-DC converter to the vehicle 12V on-board network that supplies the standard consumers such as the headlamps and the comfort systems. In order to guarantee a constant high degree of electrical efficiency, the DC-to-DC converters are cooled by water via an additional low-temperature circuit.
Special power electronics systems were required for the operation of the three-phase alternating current electric motor in the high-tension direct-current network; the inverter was located in the engine compartment. Since the power electronics also heated up through the electrical current created, the system was also integrated in the low-temperature cooling circuit. In terms of power electronics, Mercedes-Benz favoured a standardisation of all components, so that these could be combined efficiently cross-range with different electric motors and different types of batteries.
The Vision E 300 BlueTEC HYBRID diesel hybrid concept car, also presented at the 2009 International Motor Show, was an important milestone on the road towards the plug-in hybrid car. Like the S 400 HYBRID and the Vision S 500 plug-in HYBRID, it was based on the Mercedes-Benz modular hybrid design principle. In this near-series study, the 2.2-litre 4-cylinder diesel engine was combined with a 15 kW (20 hp) hybrid module, like the one used in the S 400 HYBRID, but which also made it possible to drive under electric power alone. With this drive configuration, the Vision E 300 BlueTEC HYBRID required only 4.5 litres of fuel per 100 kilometres, representing carbon dioxide emissions of just 119 grams per kilometre for an output of 165 kW (224 hp) and an outstanding torque of 580 to 600 newton metres (in both cases urban/extra urban combined), of a level equal to that of contemporary six-cylinder diesel- powered cars.