Mercedes-Benz F600 Hygenius

Technology: The latest from the future

Drive: fuel cell drive made more efficient and practicable than ever
Body concept: compact-class car offering luxury-class comfort
Seats: new concept for excellent child safety and a healthy posture
Dashboard: virtual displays to reduce the strain on the eyes

“The future of the automobile" - this Mercedes slogan takes concrete form in the F 600 HYGENIUS. The research vehicle with its advanced fuel cell drive gives a look forwards to the future of motoring as envisioned by Mercedes-Benz: a future that is completely emission-free and based on a new energy source that is not dependent in any way on the earth's resources of crude oil.

It has only been eleven years since the world's very first fuel cell-powered vehicle took to the roads - a very short time indeed in view of the immense research and development challenge associated with turning this pioneering drive system into automotive reality. Premiered in 1994, NECAR 1 (New Electric Car) was a small van, packed to the roof with some 800 kilograms of componentry that made up the fuel cell power plant. Top speed was 90 km/h and the operating range just 130 kilometres. Today, over 100 Mercedes fuel cell models are being put through their paces in day-to-day operation by customers around the world: "F-Cell" passenger cars built on the platform of the A-Class, small vans and urban buses. They have already covered some 1.5 million kilometres between them and continue to supply vital data on a daily basis that is channelled into the continued advancement of this technology.

This wealth of practical experience and the expertise of a team made up of some 150 scientists and automotive engineers fuelled the development of the new improved fuel cell drive unit in the F 600 HYGENIUS, which represents a major milestone en route to bringing this technology up to series-production standard.

The powerplant aboard the F 600 HYGENIUS, which generates electrical power, heat and pure water from the chemical reaction between hydrogen and oxygen (air), comprises four stacks made up of a total of 400 individual fuel cells. Inside the cells, the chemical elements flow through the fine channels of the bipolar plates: hydrogen on the positively charged side (the anode) and air on the negatively charged side (the cathode). The bipolar plates are separated by a wafer-thin plastic film coated with a noble metal catalyst that allows only the positively charged hydrogen ions (protons) to migrate to the cathode where they react with the air to form water. The film is impermeable for the negatively charged electrons which migrate to the cathode via an external connection instead: this causes the electric current to flow that is used to power the F 600 HYGENIUS.

Several key details of this emission-free process have been optimised by the experts at Mercedes. The bipolar plates are now made from metal plates measuring just 0.15 millimetres thick instead of the graphite material used previously. This improves conductivity and strength at the same time as reducing the amount of space required: as a result, the stacks have been made around 40 per cent smaller compared to the system in the A-Class "F-Cell".

With a view to reducing the drive system's size and weight, while also boosting its power and efficiency, Mercedes-Benz developed a new electric turbocharger to feed air to the fuel cell. This replaces the previous screw-type supercharger which was some three times larger, seven times heavier and considerably noisier.

Intelligent water management enables starts at temperatures as low as -25°C

The only by-product resulting from the chemical reaction between hydrogen and air in the fuel cell is water. This water has an important function to fulfil as it keeps the plastic film between anode and cathode moist, which is essential to maintaining its proton conductivity. Previously, the water produced by the fuel cell was caught in the discharge air and injected in fluid form into the supply air - with the major drawback that the fuel cells froze at sub-zero temperatures.

The improved system used in the F 600 HYGENIUS is notable for its newly developed plastic film that requires far less moisture. This allows the engineers to fit a far simpler humidifying device comprising hollow-fibre bundles that are permeable to water vapour but impermeable to air. After being compressed in the turbocharger, the fresh air flows through the humidifier and absorbs just as much moisture as is needed for the proton exchange at the plastic films. The permanent airflow also helps to "dispose of" the water produced by the reaction and keep the cells free of liquid water. The discharge air is also directed through the hollow-fibre modules where some of the water vapour absorbed in the stack is dissipated to the compressed supply air.

Moist air instead of water, breathable dehumidifiers instead of condensers and pumps - this intelligent principle for water management in the fuel cell represents a major breakthrough as far as cold-start capabilities are concerned. The newly devised gas-to-gas humidifier and the new improved plastic film mean there is no liquid water left in the stacks when the driver switches off the drive unit at the end of the journey. Consequently, there is no risk of the system freezing up in winter; far from it in fact, with the fuel cell drive springing to life even at arctic temperatures as low as - 25° Celsius.

Efficiency climbs to 60 per cent, fuel consumption drops to 2.9 litres

Quite apart from representing a further major step towards full production maturity, these innovations and others make a very healthy difference to the drive system's energy efficiency. Fitted in the F 600 HYGENIUS, the fuel cell system achieves an efficiency factor of around 60 per cent even at partial throttle, making it far more economical than conventional combustion engines which only attain their maximum efficiency of 45 per cent at full throttle.

Expressed in terms of diesel fuel, the latest research vehicle from Mercedes consumes the equivalent of just 2.9 litres per 100 kilometres.

Booster effect for snappy acceleration

Such exemplary economy is also the result of an intelligent energy management system which adapts the drive concept to the driving situation as it changes. Consequently, the F 600 HYGENIUS works in a similar way to a hybrid car:

During normal driving (at a constant speed), the electric motor is supplied with energy from the fuel cell directly. This puts a maximum of 66 kW/90 hp on tap, with any surplus energy being used to charge the high-voltage battery.
When accelerating from standstill or overtaking, the high-voltage battery cuts in to supply energy to the electric drive unit as well. This booster effect increases the maximum power available to 85 kW/115 hp.
When parking or manoeuvring, the battery acts as the sole source of energy with a peak output of 55 kW/75 hp.
During vehicle braking, the electric motor automatically switches function to act as a generator which charges the battery. This intelligent system of recuperation allows drive energy to be recovered.

700-bar hydrogen reservoir extends range to 400 kilometres

The entire fuel cell system fits underneath the occupant cell of the F 600 HYGENIUS, including a newly developed tank which can store up to four kilograms of hydrogen at a pressure of 700 bar. Both the reservoir capacity and the storage pressure have therefore been approximately doubled compared to the A Class "F Cell" vehicles, extending the maximum operating range to over 400 kilometres.

For the first time in a fuel cell vehicle, Mercedes-Benz is using a high-power lithium-ion battery to store electrical energy. This delivers an output of 30 kW in continuous operation and up to 55 kW at maximum throttle, more than double the power output of the former nickel-metal hydride batteries.

The electric motor fitted to the research vehicle's rear axle has been developed in house, drawing on all of the Stuttgart engineers' experience with the fuel cell drive. Unlike the asynchronous motors fitted in the past, the new unit is a permanently excited synchronous motor whose constant power output of 60 kW/82 hp delivers 250 Newton metres of pulling power, far more than a comparable combustion engine is capable of. The rear-mounted electric motor can even deliver brief power spurts of up to 85 kW/ 115 hp with torque peaking at 350 Newton metres. Here is a summary of the data for the energy and drive system at the heart of the F 600 HYGENIUS:

Electric motor
Constant output; peak outputTorque

Permanently excited synchronous AC motor
60 kW/82 hp; 85 kW/115 hp
250 - 350 Nm

Energy storage device
Voltage
Output

Lithium-ion battery
200 - 270
V30/55 kW

Hydrogen reservoir
Hydrogen capacity
Pressure

4 kg
700 bar

Fuel cell

4 stacks of 100 cells

Energy consumption

Equivalent of 2.9 l diesel/100 km

Range

Over 400 km

Top speed

Approx. 170 km/h

Fuel cell paves the way for new forms of clean energy supply

The fuel cell points the ways forwards into a future with a guaranteed energy source. Hydrogen is the most commonly occurring of all chemical elements and is renewable, meaning that its manufacture has no implications for the environment. Fuel cells convert hydrogen into electrical energy extremely efficiently in a process that produces neither pollutants nor the greenhouse gas carbon dioxide. To put it in a nutshell: hydrogen is the fuel which, in the opinion of the experts, holds the greatest potential for the future.

For Mercedes-Benz, hydrogen-powered fuel cell vehicles represent the culmination of a five-stage plan targeting mobility that is both free from dependency on crude oil and free from emissions. Consequently, the Stuttgart-based manufacturer is investing heavily in this technology and has undertaken to make it marketable some time between 2012 and 2015. The fuel cell will do more than just put an end to the reliance of motor vehicles on crude oil resources: the new F 600 HYGENIUS, for instance, also presents motorists with new possibilities for energy usage which would previously have been inconceivable.

At the weekends - when camping or picnicking - the fuel cell can power the coffee percolator, refrigerator, electric grill, television or party lights.
During the working week, tradesmen are simply able to connect machines and tools up to the fuel cell vehicle's 110/220V power socket, while business executives can take their computer, printer and fax machine with them on business trips and work anywhere they need to.

Passengers even reap the benefit of the fuel cell's power en route: drinks placed in the cup holders between the front seats can be kept chilled or hot using energy from the powerplant.

In theory, the electrical output of the fuel cell in the F 600 HYGENIUS (66 kW) would be sufficient to supply power to several detached houses. This is an interesting concept which merits further investigation.

The high tech of tomorrow fitted into a realistic compact car concept

The Stuttgart manufacturer takes the clean-running, hydrogen-fuelled drive seriously so it had its project planners devise a concept that is as practical as it is practicable: a sophisticated compact car designed with families in mind. By so doing, the engineers have delivered solid proof once again that the trendsetting fuel cell drive can be integrated into a vehicle of this size without having to compromise levels of spaciousness or passenger comfort and safety in any way.

On the contrary, in fact: by positioning the drive components and the energy storage devices under the floor, the majority of the body is dedicated to the occupant compartment. As a result, the level of space and comfort and the freedom of movement are exceptional by compact-class standards. Take the spacing between the driver's seat and the rear seat, for instance: the distance of 945 millimetres is a figure normally associated with larger luxury cars.

Added to this is the research car's unprecedented practicality and seating versatility. Not only can the individual seats in the rear be adjusted from side to side or removed completely, they also have a fore-aft adjustment range of 400 millimetres, producing limousine-like proportions in the rear and increasing the seat spacing to as much as 1345 millimetres.

New seating concept designed for taking better care of children

Children and their safety formed a further focal point during the design of the interior. Backrests that have been designed to swing forwards simply and support a rearwards-facing occupant present new possibilities for child safety and simplify the task of attending to younger children when travelling by car. With the front passenger seat backrest swung forwards, infants can be placed in a child seat that is then locked into place on the front passenger seat cushion by means of the ISOFIX anchorage system. This secure, rearwards-facing positioning gives the infant eye contact with an adult sitting in the right-hand or left-hand seat in the rear.

The rear seats likewise feature reversible backrests that make them a solid basis for locking child seats into place on their seat cushions.

Two-piece driver's seat backrest protects spine and intervertebral discs

Yet another seat innovation being showcased for the first time by Mercedes-Benz in the F 600 HYGENIUS is designed to improve driver comfort and posture on long journeys: the driver benefits from a two-piece backrest that is designed to relieve the strain on the spine and intervertebral discs. This is the task of movable back cushions with electric motors that enable precision adjustment to the contours of the driver's back. Not only can the cushions' shape be adapted, they can be repositioned horizontally by up to 60 mm and vertically by up to 80 millimetres. As a result, the backrest wraps around the entire upper body, lending much more effective support than conventional car seats, particularly in the midriff region.

Once it has been moulded to the occupant, the backrest follows any body movements like a fitted suit, relieving the strain on the discs in any seat position. If the driver leans further back, the lower section of the backrest automatically pivots forwards to keep the pelvic area more erect. The experts at Mercedes who have developed this revolutionary new seat technology together with medical experts have christened their latest contribution to driver comfort on long journeys "active seating".

The F 600 HYGENIUS is more than a safe, comfortable family car boasting tomorrow's drive technology, it is also intended as a versatile companion for leisure-time activities. For example, an AC power socket can be found in the tailgate which supplies clean energy from the fuel cell whenever the vehicle is parked up.

And when it's time for a break in a lay-by or enjoying a picnic by a lake, a seating area for two that is protected from the elements can be set up in the rear of the vehicle. As soon as the tailgate lifts, the rear bumper drops down, automatically pulling out with it the luggage compartment floor which doubles as the seating area. The picnic area is completed by pulling two extending panels made from hard-wearing fabric out from under the load compartment floor and hooking them into the roof liner to form two supports to lean back against.

Two-piece tailgate with compact opening concept

The tailgate concept that has been devised by the F 600 developers is equally stylish and intelligent. It solves an everyday dilemma encountered by many motorists: opening a large tailgate in cramped spaces, such as a garage. In this situation, a press of the button on the research vehicle's electronic ignition and door key is enough to open the tailgate in three phases with the assistance of powerful electric motors:

Phase 1: the catch is released and the tailgate starts to open
Phase 2: at the halfway point, the bottom section of the tailgate folds inwards until it automatically locks into position
Phase 3: now folded so that it is only half the size, the tailgate swings fully open, requiring far less space to do so.

The new hinge mechanism for the front doors offers similar space-saving benefits: by swinging upwards at a slant when they are opened, the doors take up less space, allowing for easier access to and from the vehicle even when parked in tight parking spots. Two gas-filled struts hold the door open in any position, without the need for any further controls to be operated.

Video monitoring for leaving the vehicle safely

A video system has been added to make getting out of the vehicle safer for passengers: cameras integrated into the exterior mirror housings keep an eye on traffic to the side of and behind the F 600 HYGENIUS and can detect a car or a bicycle that is approaching from behind. If this is the case, a warning symbol flashes up in the mirror glass and the doors are briefly disabled to avoid the risk of a collision with the other road user passing by.

Out on the road, the video cameras monitor the blind spots behind the F 600 HYGENIUS which are not covered by the exterior mirrors and warn drivers who are about to change lane if a vehicle is approaching from behind.

PRE-SAFE® knee bolster protects front passenger prior to a collision

On the safety front, the F 600 HYGENIUS also gives a preview of how the multi-award-winning Mercedes occupant protection system PRE-SAFE® will evolve in years to come. This system swings into action prior to an impending accident to prepare both the car's occupants and the vehicle itself for the impact. In the new Mercedes-Benz S-Class, for instance, the front seat belts are pulled taut, the bolster cushions in the seats inflated and the seats themselves adjusted into a more favourable position so that the seat belts and airbags are able to protect the occupants as effectively as possible.

Future PRE-SAFE® concepts for readying the occupants even more effectively in advance of an imminent collision include knee protection that extends automatically to brace the front passenger and prevent him or her from sliding forwards underneath the seat belt on impact. The F 600 HYGENIUS has been equipped with just such a system. When the risk of an accident is detected, the knee bolster extends out of the bottom of the dashboard on the front passenger side. As with the PRE-SAFE® belt tensioners, the knee bolster also has a reversible design, meaning that if the accident is averted it is retracted into the dashboard again.

The PRE-SAFE® head restraints fitted in the research vehicle work along the same principle: if a collision seems imminent, the side bolsters fold forwards automatically to hold the occupants' heads more securely.

Dashboard switch can discern driver from front passenger

Human Machine Interface, or HMI for short, is the technical name given to a development challenge which Mercedes-Benz is tackling fervently. The aim is to adapt technology to humans by developing an operating concept that makes technology easy, safe and intuitive to use, and which maximises driver information whilst minimising driver distraction. The new S-Class from Mercedes-Benz has already taken the first few steps in this direction and the F 600 HYGENIUS now displays further ways of optimising operation.

The F 600 developers involved in this field work on the principle of "less is more". A small number of buttons and switches gives the driver fingertip control over the functions that are used most frequently: transmission, automatic climate control, navigation system, audio system and telephone. These buttons are clustered together in a control panel in the centre of the dashboard where they can be reached just as easily by both the driver and the front passenger. As soon as a button has been pressed, the COMAND display switches over to the desired function.

Ergonomically positioned in the centre of this control panel is a push/turn control knob including a further special feature: it can automatically detect whether it is being touched by the driver or the front passenger, whereupon it activates the climate control for the left or right side of the vehicle as appropriate. Both the COMAND display and the temperature indicator in the push/turn control knob change instantly, enabling both occupants in the front to program their personal climate control settings.

This new form of user recognition is based on the electrical signals transmitted in the skin: the instant the front passenger touches the push/turn control knob in the centre, a data circuit closes between the control knob and a sensor mat in the seat cushion, switching the climate control to the settings for the front passenger side. The COMAND screen can also be swivelled to the side at the push of a button, to give the front passenger a better view of it and prevent the driver from becoming distracted.

All other operating functions and personal settings are the task of the COMAND controller, as fitted in the new S-Class. In the F 600 HYGENIUS, the controller slides out of the armrest between the two front seats whenever required and allows straightforward navigation through the COMAND system's control menus. As in the new Mercedes flagship model, user navigation is based on a simple, easy-to-grasp principle: sub-menu functions or lists are opened by pressing the controller, individual items within the list are selected by turning the controller or pushing it up or down and then activated by pushing it again. To close one of the lists, the user merely has to slide the controller sideways or press the "Return" button.

Virtual displays with mirror projection go easy on the eyes

The trailblazing technology deployed for the two colour displays in the dashboard sees the F 600 developers focus for the first time on an issue that affects a large number of motorists: eye accommodation. This is what happens when the eye has to frequently adjust between looking at close-up objects and objects in the distance, e.g. when constantly switching between the cockpit instrumentation and the traffic on the road further ahead. Investigations have shown that eye accommodation can lead to strain and weariness on longer journeys.

It was with this in mind that the research engineers decided to develop virtual displays that enhance driver-fitness safety and reduce driver strain. The images in the displays are diverted and enlarged by means of two mirrors before being projected to appear at a point 1.40 metres in front of the driver. To look at the information in the displays, there is therefore no need for the driver's eyes to readjust from distance viewing to close-up viewing. This places less strain on the eyes, representing a useful contribution to improving driving safety, as verified by scientific studies.

Buttons in the door panelling allow both driver and front passenger to pivot the displays in a vertical and a horizontal plane so that their position is adjusted to suit the seat settings and the occupant's stature.

High-power light-emitting diodes adapt to the driving situation

Headlamps with high-power LEDs enhance the driver's night-time vision and help to avoid accidents. The LEDs are distributed over three projector modules whose lenses spread the light beam evenly over a wide area. The light module in the centre is activated as required, depending on the driving situation, and also assumes additional functions, such as main beam, the Active Light System and the cornering light. All of the various lighting features are performed simply by switching individual LEDs on and off electronically, thereby eliminating the need for moving components, such as those currently fitted for the Active Light System.

For the brake lights and tail lights, Mercedes-Benz has used a total of 15 high-power LEDs whose light is dispersed over a wide area by means of optical lenses. When the driver depresses the brake pedal, the illuminated area enlarges sixfold compared to the tail light, making the brake lights even more conspicuous for following traffic. In addition to this, flashing LED brake lights are activated in emergency braking situations to provide an early warning to drivers behind and reduce the risk of them ramming into the back of the car.

Trusted production technology tailored to the new vehicle concept

The chassis of the F 600 HYGENIUS is built around tried-and-tested series-production components which Mercedes-Benz has adapted to the new drive concept. This means a McPherson front suspension with steel springs, electrical power steering and internally ventilated, perforated brake discs, plus a multi-link independent rear suspension with steel springs and a custom-designed steel axle carrier for fitting the electric motor. The wheels of the Mercedes research vehicle are shod with 215/45 R 20 tyres which have been developed and manufactured especially for the F 600 HYGENIUS.

The key chassis data at a glance:

Axles

McPherson strut front suspension

Multi-link independent rear suspension

Brakes

Four-piston fixed-calliper brakes

Internally ventilated brake discs front and rear

Brake booster with electric vacuum pump

Electric parking brake acting on the rear wheels

Wheels

7 J x 20 ET 45 light-alloy wheels

Tyres