Climb in, start, drive off and, as well as exemplary efficiency, on request experience via kickdown the special acceleration of the electric motor - this is how easy hybrid driving with the new S 500 PLUG-IN HYBRID is. For in everyday use it moves just as easily as any other automatic transmission car.

In the background, the intelligent operating strategy automatically selects the ideal combination of internal combustion engine and electric motor and in so doing not only adapts its strategy according to the charge status of the battery; in transmission mode E+ it also foresightedly adjusts it according to the traffic or route. But anyone wanting to can also intervene manually and with the aid of four operating modes and three transmission modes regulate the hybrid interplay themselves. Here, what is known as the haptic accelerator pedal supplies the driver with feedback on the switch-on point of the combustion engine or signals via a double impulse when they should take their foot off the accelerator for sailing and recuperating.

For efficient operation, foresighted driving, avoiding unnecessary braking and accelerating manoeuvres, has always been the best strategy. This gains an all new importance in a hybrid model: braking manoeuvres serve not only deceleration, but can also be used to recuperate energy. And the route has considerable influence on the most efficient charging and discharge of the high-voltage battery. The intelligent operating strategy supports the driver comprehensively yet unobtrusively to achieve the most efficient driving style. The control strategy, for example, seeks to ensure that the battery, if at all possible, is flat at the end of an uphill stretch so that it can be recharged going downhill. Another key point is the requirement that urban areas be reached with a fully charged battery, if possible, so that the vehicle can be operated in stop-and-go traffic electrically - frequently and efficiently.

In the S 500 PLUG-IN HYBRID the intelligent operating strategy basically covers these three areas:

  • route-based: automatically or by way of four operating modes

  • driver-based: by way of three transmission modes

  • traffic-based: with the aid of radar.

Four operating modes and three transmission modes

By means of operating mode and transmission mode switches next to the Controller on the centre console it is possible to switch between four operating modes. A display in the middle of the instrument cluster tells which mode is currently selected. Here an overview of all four operating modes:

  • Hybrid: As the name indicates, this standard mode offers hybrid driving, i.e. combines the operation of electric motor and combustion engine. The extent to which the electric motor is used to optimise consumption, or with boost function for especially dynamic acceleration, depends - apart from the customer's driving style - on the battery charge status and the chosen transmission mode. Three transmission modes are available in this operating mode and can be activated using the transmission mode switch:

    • Transmission mode E (Economy) is standard; the electric motor is used for both the benefit of efficiency and for driving pleasure. A power reserve is retained for the electric motor so that maximum additional thrust can be provided.

    • In transmission mode E+ (Economy +) the objective is maximum fuel economy; all features of the intelligent operating strategy are active in E+. The greatest possible advantage is taken of the hybrid's energy efficiency. For example, the vehicle sails as much as possible during coasting, while energy is increasingly recuperated only upon approaching another vehicle travelling ahead. Transmission mode E+ additionally makes use of radar technology - for details see the section below on "traffic-based operating strategy".

    • In transmission mode S (Sport) the sporty features of the drive system dominate. The transmission selects the shift points to benefit agility. This mode does without purely electric driving. The larger amount of electrical energy available because of this is used for the electrically supported boost function.

  • E-mode: In this operating mode the S 500 PLUG-IN HYBRID runs purely electrically as much as possible. To ensure that the driver does not inadvertently engage the combustion engine by stepping on the accelerator, the haptic accelerator pedal with pressure point is automatically activated in this mode. The combustion engine engages only when the driver overcomes the pedal's distinct pressure point.

  • E-save: Here the charge status of the battery is preserved as it was when this operating mode was activated. For example, a fully charged battery can be held available if purely electric driving in a big city is on the agenda later. Electric driving in especially favourable situations, for instance after brief stops, is still permitted, but is metered so that the charge status does not fall below the value set by pressing the button.

  • Charge: Here the high-voltage battery is charged during vehicle operation with the aid of the internal combustion engine. Electric driving and boost operation are completely dispensed with. Under optimal conditions a run-down high-voltage battery can be fully charged in just about half an hour. As soon as the high-voltage battery is fully charged, the system automatically switches to E-save mode.

Route-based operating strategy

The route-based operating strategy takes the decision for the optimum sequence of operating modes for a route off the driver's hands. If the exact destination is known because the relevant data has been entered into the navigation system, charge and discharge of the high-voltage battery are controlled to ensure the optimal use of energy on the overall route, for as much as 1000 kilometres. One objective is to use the battery's energy content to drive uphill while recharging the battery through recuperation on the downhill stretch. The system uses data from the COMAND Online navigation system to calculate the recuperation potential of the road ahead. For example, the data provides information about the route profile and speed limits ahead in a one-metre grid for up to seven kilometres in advance.

If on the other hand the destination is not known, an assumed route is taken as a basis using likely turn-offs. In this case the system computes the probability depending on the road category. If, for example, the hybrid vehicle is travelling on a motorway, the system assumes that it will remain on the motorway for the next seven kilometres.

Traffic-based operating strategy

In transmission mode E+, during electric operation the overrun torque is reduced to a minimum to enable sailing as often and as long as possible. However, heavy braking after a long sailing phase, or premature sailing resulting in the need to restart the engine, are counterproductive. Consequently, the system makes use of radar information in bumper-to-bumper traffic in order to get its bearings from the vehicle travelling ahead.

The distance from the vehicle ahead and the speed difference are recognised with the aid of radar sensors. At exactly the moment when releasing the accelerator pedal would lead to optimally fuel-efficient "docking" onto the vehicle ahead, the driver receives a recommendation, in the form of a noticeable double impulse in the haptic accelerator pedal, to back off the accelerator.

If the driver accepts the recommendation and electric operation is available, the combustion engine is switched off and disconnected from the drive system. The vehicle then sails. If the vehicle ahead reduces its speed or the gap becomes smaller for some other reason, radar-based overrun torque control sets in. Increased recuperation by the electric motor correspondingly changes the gap to the vehicle ahead - and recovers energy.

distributed by