It is described as “sailing” – and that’s exactly what it feels like as the Mercedes-Benz S 550 e plug-in hybrid purrs smoothly, and almost silently, across the Øresund Bridge. When it was opened in 2000, the nearly eight-kilometre cable-stayed bridge across the Øresund Sound between Denmark and Sweden was hailed as a triumph of engineering. The same claim can be made of the vehicle in which I am crossing it: an opulent luxury sedan from Mercedes-Benz that happens to be the company’s first plug-in (externally rechargeable) hybrid model. Smooth and effortless propulsion, particularly in the engine-off “sailing” mode, is one of its specialties. A discreet double vibration from the haptic accelerator lets me know when it’s time to lift off the gas and enjoy that special sensation of light and effortless propulsion. What is actually happening is simply that the internal combustion engine has been switched off and decoupled from the powertrain, leaving only the electric motor engaged.
Using topographical information, the navigation system helps select the optimal operating strategy for the electric motor and internal combustion engine.
Although Mercedes-Benz has already put a hybrid S-Class model on the road, it is the plug-in hybrid S 550 e that gives the “S” in the badge an added attribute: superior sustainability. Two things stand out above all. First, the virtually seamless interaction between the 329-hp V6 bi-turbo engine and the 114-hp electric motor mounted directly on the seven-speed automatic transmission. Second, the way information is continuously circulated between the powertrain and the electronic systems, enabling the electric motor and internal combustion engine to work together in perfect tandem and in perfect alignment with the route topography and traffic conditions. Based on information about everything from gradients to speed limits and congestion, the hybrid powertrain calculates when to deploy the engine or the electric motor for minimum emissions.
That exchange of information enhances both efficiency and safety. For example, when a vehicle ahead is slowing down and the gap is closing, the S-Class is prompted to activate its radar-based recuperation system to ensure the electric motor acts as a generator while also maintaining a safe following distance. The display shows the direction of energy flow: White arrows pointing toward the battery indicate that the electric motor is recovering energy and feeding it to the battery. This strategy can be deployed whenever the Hybrid drive mode and the E+ transmission mode are engaged. In this combination, the driver knows that the luxury sedan can always be relied on to adopt the most energy-efficient powertrain strategy all by itself.
Mind the gap: Keeping a safe distance is left to the recuperation system, not the driver’s discretion.
The S 550 e is the most intelligent model ever to emerge from the luxury S-Class stable, in a career that now dates back more than 40 years. Throughout that time, the S-Class has been a byword for cutting-edge automotive engineering. In 1978, it featured the world’s very first electronically controlled anti-lock braking system (ABS) in a production car, in 1981 the first driver airbag was fitted and then, in 2005, it pioneered radar-based Brake Assist. Small wonder the current S-Class is the world’s top-selling high-end sedan, with sales exceeding 100,000 vehicles.
Quiet time: After pressing the start button, the initial silence of electric drive can be surprising.
After a quiet coffee break, it becomes clear that cruising through the city is an experience likewise verging on the serene. Electric drive is automatically selected when pressing the start button at the beginning of the journey, and that initial silence can be surprising. At first, you might think nothing is happening. But then you notice the instrument cluster has already sprung to life. And electric power is not only about “sailing” or cruising – it can also be used to provide boost power. The plug-in hybrid offers this function whenever the S transmission mode is selected. Activated by pressing smartly on the gas, the boost feature uses the electric motor to supplement the combustion engine for increased performance.
On the highway, I try it out and just love the way it thrusts me back in my seat. The car quickly picks up speed and the arrows in the energy flow display show red – a sign that significant quantities of energy are flowing out of the rear-axle-mounted battery pack.
The S 550 e is every inch a trailblazer. By 2017, Mercedes-Benz plans to offer as many as three different hybrid models. Daimler board member Thomas Weber recently commented that hybrid drive will soon be as normal as gasoline or diesel models are today.
Back in town, it’s time to plug the cable into the charging port, located behind a discreet flap on the rear bumper. Depending on socket rating, charging takes some two to four hours. Within the lifetime of this model generation, the plug-in hybrid S-Class is set to be joined by an “unplugged” version with a wireless, inductive charging system. Now that’s real power.