Plug-in hybrids. The best of two worlds

The combination of internal combustion engine and electric motor offers our customers the best of two worlds: In the city, they can drive for up to 33 km on all-electric power dependent on the vehicle; on long distances they additionally benefit from the ranges of the combustion engine. In this way, hybrid technology leads our customers gradually to electric mobility.

Advances in battery technology will also result in greater ranges in the coming years: We will present the next generation of plug-in hybrid technology with the facelift of the S 500 e as early as in 2017, achieving all-electric ranges of more than 50 km for the first time. (S 500 e: Fuel consumption, combined cycle: 2.8 l/ 100 km; CO2 emissions, combined: 65 g/km)

Our hybrid initiative is decisively facilitated by our modular hybrid concept for Mercedes-Benz passenger vehicles: It has a scalable design and can be carried over to a host of model series and body styles as well as to left-hand-drive and right-hand-drive variants. City streets, country roads or motorways – thanks to an intelligent operating strategy, our vehicles are able to recognise the driving situation and tailor the fuel consumption and comfort functions to it. Learn where we are in terms of hybridisation and what is still to come in future here.

The GEN 3 hybrid powertrain

The plug-in product initiative at Mercedes-Benz is in full swing: Today, we already have eight plug-in hybrids in our product range, and by 2017 there will be ten. We will set the next milestone with the launch of our new hybrid powertrain of the third generation (GEN 3) in the E 350 e in autumn 2016. (E 350 e: Fuel consumption, combined cycle: 2.5-2.1 l/ 100 km; CO2 emissions, combined: 57-49 g/km)

Our engineers focused predominantly on three objectives in the development of the GEN 3 hybrid powertrain:

The objectives of our engineers: The result:
1. lowering the fuel consumption further while increasing the output; 1. The combination of 9G-TRONIC plug-in hybrid transmission and the latest generation of electric motors ensures benchmarks in terms of consumption, ride quality and dynamics. The executive saloon can operate for up to 33 km on all-electric power depending on the individual driving profile. With a fully charged high-voltage battery at the start, this translates into a NEDC-based calculated fuel consumption of just 2.1 litres per 100 km. At the same time, the E-Class has a high towing capacity of up to 2.1 tonnes.
2. designing a modular drive system, which can be used in various Mercedes-Benz vehicles with rear-wheel drive, and 2. The development of the traction head focused above all on a compact design that only minimally increases the length of the conventional transmission. The extremely compact design of the 9G-TRONIC hybrid transmission means it can be used in any Mercedes-Benz model series with rear-wheel drive.
3. delivering a powerful hybrid powertrain without sacrifices for the passenger (e.g. towing capacity), and with a preferably large boot volume. 3. Boot volume: Despite including a powerful high-voltage battery the developers have succeeded in providing a boot volume of 400 litres.

Hybrid transmission and hybrid traction head

The hybrid transmission with hybrid traction head forms the heart of the hybrid vehicle. The basis of the GEN 3 hybrid powertrain is the 9G-TRONIC automatic transmission. The familiar nine-speed torque converter automatic transmission is expanded with an innovative and compact power-end concept for electric applications.

In addition to the conventional transmission, the hybrid traction head includes the torque converter lockup clutch, the electric motor and a decoupling clutch for decoupling the combustion engine for all-electric driving. It has a modular design and thanks to its compact dimensions can be used in any Mercedes-Benz model series with longitudinally installed powertrain. In principle, the engineers succeeded in designing a transmission with a standardised traction head that meets the load condition requirements of a GLE-Class in the installation space of a C-Class.

Click here to find out more about the components of the hybrid traction head:

(C 350 e: Fuel consumption, combined cycle: 2.4-2.1 l/ 100 km; CO2 emissions, combined: 54-48 g/km)

In the plug-in hybrid vehicle, a whole series of other components play a crucial role in addition to the hybrid transmission with hybrid traction head. With GEN 3 of the hybrid powertrain, we have succeeded in using standard high-voltage components from the modular strategy independent of the model series, and consequently also improving the cost situation.

How does the interplay between the electric motor and the combustion engine work?

  • When the hybrid vehicle is in all-electric mode, the clutch is disengaged, the combustion engine is decoupled and switched off.
  • During energy recovery, the clutch also remains disengaged, with the electric motor acting as a generator that converts mechanical energy into electric energy for charging the battery.
  • In hybrid mode, the clutch is engaged. The intelligent hybrid control operates the combustion engine and the electric motor in unison with regard to comfort and efficiency criteria.
  • In gliding mode the clutch is disengaged and the combustion engine is switched off. The vehicle coasts without the drag losses of the combustion engine.
  • Boost: The power of the electric motor is added to the full power of the combustion engine.

The plug-in hybrid offers four operating modes:

  • Hybrid mode: All hybrid functions such as electric mode, boost and recuperation are available and used to optimise consumption.
  • Electric mode: Used for all-electric driving – for example, in city centres or because the high-voltage battery is sufficiently charged for the distance to be driven.
  • E-Save mode: The charge level of the high-voltage battery is maintained – for example, because all-electric driving is required later in a low emission zone.
  • Charge mode: Used to recharge the high-voltage battery with the combustion engine, for example, to be able to drive in all-electric mode later in a low emission zone.

Intelligent drive management

The powertrain management of the new E-Class is distinguished by intelligent anticipatory functions, which, among other things, significantly reduce fuel consumption and increase the electric range in electric mode. These include, for example, the radar-based recuperation function, an anticipatory shift and operating strategy, a route-based operating-mode strategy and ECO Assist, which communicates with the driver via the haptic accelerator pedal.

In terms of technology, the functions are based on radar, camera and navigation data, and use both near as well as far anticipatory time horizons.

1. Near anticipatory time horizon

The recuperation function was further advanced to maximise energy recovery. On the previous plug-in models, this function varied the overrun torque based on the radar sensor information relating to a vehicle in front.

On the new E-Class, the system also factors in the route information from the navigation system and camera data in addition to the radar information about the vehicle in front.

Based on these data, the vehicle speed in overrun mode is adjusted and the energy consumption is further improved. This not only increases the energy-recovery torque when the driver approaches a slower vehicle, but also when approaching posted speed limits or on downhill gradients.

If gliding is possible, the drive system automatically switches to gliding mode with the combustion engine switched off and decoupled from the drivetrain to avoid drag losses.

If the system recognises an upcoming speed limitation, the speed is likewise adjusted through recuperation. These functionalities use a double pulse of the haptic accelerator pedal to let the driver know when it is better from an energy-efficiency standpoint to lift off the accelerator pedal and hand over control to the intelligent recuperation feature.

Route based Operating Strategy

2. Far anticipatory time horizon

To operate the plug-in hybrid even more efficiently, the operating strategy also considers anticipatory information with a far time horizon. To this end, the course of the route is analysed and the all-electric mode as well as the recharging and cooling strategies are adapted to the route profile. When route guidance is active, the route profile is calculated with the aid of the navigation system, and the route-based operating-mode strategy selects the right operating mode.

Thermal Management

3. System identifies cities to be traversed

Apart from the developments in vehicle speed and the route topography, the system also factors in where city driving is required when planning the amount of available electric energy. The result: The system predominantly selects electric driving in urban areas or when driving routes with low power requirements to prevent operating the combustion engine in inefficient areas. On route sections with higher power requirements such as, for example, high speeds on the motorway, the high-voltage battery is recharged by shifting the load point.

Intelligent thermal management: To further improve the cooling of the engine, transmission, and the high-voltage battery, power electronics and electric motor components, information about the upcoming route profile is also factored in.

A look ahead: The next hybrid generation

After the initial launch of the GEN 3 hybrid system in the E 350 e in autumn 2016, the next technology leap is already pending in 2017. Starting with the facelift of the S 500 e, the further advanced lithium-ion battery with higher capacity in combination with the yet further improved operating strategy will make all-electric ranges of up to 50 km possible for the first time. The high-efficiency battery system is supplied by the wholly owned Daimler subsidiary ACCUMOTIVE, making this the first time the company also provides batteries for plug-in hybrids from Mercedes-Benz. Further advances in battery technology will gradually increase battery capacity and thereby the range over time.

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