The Mercedes-Benz S 500 PLUG-IN HYBRID offers a system output of 325 kW and 650 Nm torque, sprints from 0 to 100 km/h in just 5.2 seconds and can drive up to 33 km purely electrically. The certified consumption is 2.8 litres/100 km, which corresponds to 65 g CO2/km emissions. The real-life consumption is also outstanding. Key elements of this impressive output are the V6 biturbo and the intelligent hybrid drive.

"The S 500 PLUG-IN HYBRID is the first luxury saloon with the performance of a V8 and the fuel consumption of a compact model. The greatest challenge in this is to translate efficiency into superior performance. In this respect there is a highly interesting parallel with our successful Formula 1 racing car, which likewise has a turbocharged V6 engine and a high-tech hybrid drive," says Prof. Dr. Thomas Weber, member of the Daimler Board of Management responsible for Group Research and Mercedes-Benz Cars Development.

Hybrid drives, the combination of internal combustion engine and electric drive, help cut overall fuel consumption and boost performance, since the electric drive replaces or supports the combustion engine whenever the engine characteristics are unfavourable - normally in part-load operation when little power is required. The experience gained with the previous vehicles from Mercedes-Benz has shown that though batteries with a higher energy content permit more frequent electric driving, they provide no added benefit from a consumption viewpoint. The capacity for braking energy recuperation determines the optimal design of the capacity and energy content of the traction battery. Recharging by the internal combustion engine cannot compensate for the additional vehicle weight resulting from an oversized battery.

For this reason, in the S 500 PLUG-IN HYBRID Mercedes-Benz combines a high-energy battery with the ability to replenish the energy storage unit via the external electric mains. The advantages of emission-free electric driving thus are brought ideally into line with the tremendous consumption advantage of the parallel hybrid - and combined with a ride comfort and handling dynamics which meet the highest standards. And a range that imposes no restrictions whatsoever on the driver.

As with all hybrid vehicles from Mercedes-Benz, the ultraefficient drive system is integrated in the overall vehicle in a way that creates no space restrictions. Major adjustments to the packaging of the overall vehicle are unnecessary - this is a big advantage for the production of the hybrid vehicles, for example, but it also poses a huge challenge for the development of the electric motor and its integration in the power head of the transmission and for the development of the power electronics and the high-voltage battery.

The hybrid transmission is based on the 7G-TRONIC PLUS 7-speed automatic transmission. The plug-in hybrid system in the S-Class is based on the Mercedes-Benz parallel hybrid modular system. The common system-specific feature is the additional clutch integrated between combustion engine and electric motor. On the one hand, it decouples the combustion engine during purely electric operation; on the other hand, if the combustion engine is employed it affords the possibility to move off drawing on the performance of a wet start-up clutch. The clutch then substitutes for the torque converter and requires no additional space owing to its complete integration in the torque converter housing.

For the stop phases of the combustion engine the hybrid system has a high-voltage refrigerant compressor, and on the 12 V side an electrically assisted steering, an electric vacuum pump and an electric auxiliary oil pump for the transmission.

Completely integrated: the electric motor

The electric motor of the PLUG-IN HYBRID has been further developed from the previous hybrid vehicles. The modular design enabled longitudinal scaling from 6 to 9 rotor plate packs. Despite its compact design the electric motor delivers an output of up to 85 kW and torque of up to 340 Nm. The permanently excited synchronous motor is fully integrated into the hybrid transmission. Stator and rotor of the internal rotor motor are cooled by transmission oil.

Power electronics and voltage transformer

The high-voltage battery feeds the electric motor through a water-cooled DC/AC converter, the power electronics. This too is a component from the Mercedes-Benz modular system and was first developed for the technology platform SLS AMG E-CELL, which went into production as the SLS AMG Coupé Electric Drive. The integration of the power electronics with an electric motor optimised for plug-in operation enables top performance in terms of comfort and output over the entire operating range.

The power electronics operate with a rated voltage of 325 V and supply 350 A maximum current, at the same time determining the position and status of the electric motor by means of a rotor position sensor as well as various component temperatures. Depending on operating situation, actuation of the electric motor is guided by the rotational speed or the torque, within the permissible limits. To optimise the effort for wiring, packaging and cooling, the DC/AC converter has been integrated into the engine space. A separate DC/DC converter at the rear of the vehicle supports the 12 V on-board power supply with an output of up to 3 kW.

With twin turbochargers: the internal combustion engine

For inherent design reasons, electric motors and combustion engines have different torque curves, which can, however, outstandingly complement each other. An electric motor makes its peak torque available as soon as it starts and can therefore compensate an internal combustion engine's weak torque in the low rev range. The electric motor and the V6 biturbo are thus ideal partners in the drive system of the S 500 PLUG-IN HYBRID.

The V6 biturbo with a displacement of three litres comes from the M276 engine family and features the BlueDIRECT injection and combustion system. Cylinder heads and block are made of aluminium. To reduce friction, the cylinder barrels are coated with the aid of the innovative NANOSLIDE process. Other engine characteristics include four valves per cylinder, a particularly quiet chain drive system with silent chains and two camshaft adjusters each for the intake and exhaust sides.

The third-generation direct injection system has a fuel pressure of 200 bar and spray-guided multiple injection with piezo injection nozzles. The on-demand vane-type oil pump cools and lubricates the engine depending on engine load and engine speed. The volume control distinguishes between a low and a high pressure level and adjusts the volume flow as required. The weight of the components of the water circuit could be reduced through the systematic use of plastic. In an extended temperature range the heating supply for the interior is preferentially served. The desired temperature is thus very quickly reached during the warm-up phase. An electric heater element ensures rapid warming of the car interior also during electric driving.

The technical data at a glance:

Model

S 500 PLUG-IN HYBRID

Internal combustion engine:

Number of cylinders/arrangement

6/V

Mixture formation

High-pressure injection, 2 turbochargers

Displacement (cc)

2996

Rated output (kW/hp at rpm)

245/333 at 5250-6000

Rated torque (Nm at rpm)

480 at 1600-4000

Electric motor:

Output (kW)

85

Torque (Nm)

340

System output (kW/hp)

325/442

System torque (Nm)1

650

Consumption combined from (l/100 km)2

2.8

CO2 emissions combined from (g/km)2

65

Efficiency class

A+

Electric range (km)

33

Charge time 20%-100% (400 V/16 A - 230 V/8 A)3 (h)

2 - 4.1

Acceleration 0-100 km/h (s)

5.2

Top speed (km/h)1

250

Top speed electric (km/h)1

140

Price (euros)4

108,944.50

1 Electronically limited, 2 In accordance with NEDC, 3Charge time at 230 V/8 A, for example at a commercially available socket. Through settings on the control element of the charging cable shorter charge times can be realised (standard setting: 8 A), provided that the power supply system is designed for this. Charge time at 400 V/16 A e.g. at a wallbox. The voltage and current ratings indicated refer to the power supply infrastructure and can be limited by the car, 4 Sales price in Germany, incl. 19 percent VAT

Depending on the power requirement and battery charge status, the S 500 PLUG-IN HYBRID drives in purely electric mode. Moving off from stationary also takes place in electric mode. This "silent start" is part of the exceptional driving experience and perfects the start/stop procedure, e.g. with noiseless starting at traffic lights. In transmission mode "S" electric driving can be excluded.

If more power is required, the internal combustion engine is started by means of a process developed specifically for hybrid drives with direct-injection petrol engines, and then is quickly and conveniently engaged by actuating the clutch, depending on operating conditions. The Mercedes-Benz starting procedure combines appropriate actuation of the starter with the ECO start/stop function of direct-injection petrol engines, in which starting is optimised by well-targeted injections and ignitions. This and the simultaneous actuation of the clutch, with its additional accelerating effect on the starting engine, make an extremely rapid start possible compared with a conventional starting procedure, ensuring a good transition from electric driving.

The internal combustion engine is shut off as often as possible for purely electric driving. But even so, in combination with the electric motor it delivers a total torque on the level of an eight-cylinder drive when such power is required.

Recuperative braking system: the electric motor as generator

The largest potential for lowering the energy consumption of hybrid drive systems lies in maximising energy recovery during coasting and braking. Upon depressing the brake pedal the deceleration is initially effected by the electric motor and not by the disc brakes. The hybrid models of the new S-Class are the first to use a recuperative braking system of the second generation. It ensures an unnoticeable overlapping of the conventional mechanical brakes and the electric braking performance of the electric motor in generator mode.

The driver's desired braking power is recorded by a pedal-travel sensor. The deceleration is dependent on the driving condition and is split into a recuperative brake-force portion and a portion to be supplied by the wheel brakes. The brake pressure on the rear axle is controlled dependent on the current recuperation potential of the drive system.

In addition, the combustion engine is switched off any time the vehicle is coasting, and its drag torque when rolling is used by the electric motor as recuperation torque. However, without depressing the brake pedal no additional deceleration torque is provided for charging the battery, and the vehicle can "sail".

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