One vehicle architecture, three different powertrain configurations: that sums up Mercedes-Benz’s near-series Concept BlueZERO trio of cars.
Two of the BlueZERO variants were on display at the 2009 North American International Auto Show (NAIAS) in Detroit—the battery-electric E-Cell and the fuel-cell-powered F-Cell. A third version with a range extender (the 1.0-L turbocharged gasoline engine from the Smart Fortwo), the E-Cell Plus, is also under development.
The three front-wheel-drive concept cars are based on the same sandwich-floor architecture used for A-Class and B-Class models. Advantages of the construction, according to Mercedes, include a low center of gravity, protection of the major powertrain components between the axles within the vehicle underbody, and an interior with “no compromises” in terms of space for five passengers and a 500-L (17.7-ft³) luggage compartment.
“The modified sandwich-floor platform provides the perfect basis for a wide model range with electric drive systems,” said Dr. Thomas Weber, the member of the Daimler AG Board of Management responsible for corporate research and development at Mercedes-Benz Cars. “We are also developing a new, additional platform for future compact models with power units based on optimized internal-combustion engines. The intelligent networking of both architectures enables us to develop our product portfolio extremely flexibly and efficiently.”
Weber noted that the first Mercedes fuel-cell cars will be produced on a small scale from 2009, with low-volume production of battery-electric cars commencing in 2010.
All three BlueZERO variants share the same design and vehicle dimensions—4223 mm (166.3 in) long, 1890 mm (74.4 in) wide (excluding mirrors), and 1593 mm (62.7 in) tall, with a 450-kg (1000-lb) payload.
More notably, though, they share modular drive components. These include liquid-cooled lithium-ion batteries with a storage capacity of up to 35 kW·h and an operating voltage of 240 to 426 V, as well as a permanent-magnet synchronous electric motor with a maximum output of 100 kW, 70 kW continuous, and peak torque of 320 N·m (236 lb·ft), 180 N·m (133 lb·ft) continuous.
The Li-ion batteries in the E-Cell and the E-Cell Plus can store enough energy for a range of 50 km (30 mi) within 30 min using a 15-kW charging unit. Charging times are doubled using a normal household outlet. Both vehicles incorporate an electronic control unit that supports intelligent charging stations and billing systems.
The E-Cell has a range of up to 200 km (125 mi), while the E-Cell Plus’ electric-only range is 100 km (62 mi). With its 50-kW (67-hp), three-cylinder engine, which is installed near the rear axle in the spare wheel well, the E-Cell Plus has an overall range of up to 600 km (375 mi) and an NEDC (New European Driving Cycle) fuel consumption of 4.5 L/100 km. The engine can recharge the 17.5-kW·h Li-ion battery via a 50-kW alternator.
The cars feature plug-in connectors to EU and U.S. standards for recharging. One contact is intended for conventional power cables that fit any household power socket; the second is suitable for connection to public recharging stations.
A new-generation fuel cell that is more compact and powerful—90 kW maximum, 80 kW continuous—than its predecessor is used in the F-Cell concept car. It can be cold-started at temperatures down to -25°C (-13°F).
“This will be the next generation where we have the system in a B-Class,” said Arwed Niestroj, Senior Manager of Fuel Cell Vehicle Operations. “We have increased tank pressures—700 bar compared to 350 bar in the [previous] A-Class—so we have higher range of 400 km now. In the A-Class, it was only 170 km. We have reduced component size by 30%. And it’s the first time using a lithium-ion battery; in the A-Class, we had nickel metal-hydride.” Johnson Controls-Saft is its partner for the Li-ion battery.
After low-volume production begins at the end of this year, “we’ll produce a small fleet to be introduced next year,” in California as well as in Europe and Japan, said Niestroj. Beyond the B-Class fleet, “we want the fuel-cell system, cost-wise, ready for series production and full commercialization. Our target is to do this by 2015. We are still checking which vehicles will be suitable.”
The system uses the most efficient energy source for a particular driving situation. For example, when maneuvering at low speeds, the electric motor uses only battery power. When accelerating, energy is provided by both the fuel cell and the battery. When braking, the electric motor acts as a generator and charges the battery.
According to the NEDC, the F-Cell is able to cover more than 400 km (250 mi) on one tank of hydrogen, consuming 2.9 L of fuel (diesel equivalent) per 100 km.
All three cars can accelerate from 0 to 100 km/h (62 mph) in less than 11 s. Their top speed is electronically limited to 150 km/h (93 mph).
The exterior design borrows characteristics from the Mercedes-Benz bionic car, and aerodynamics are improved by a closed front apron since cooling air intakes are not required. A semi-transparent, panoramic roof features integrated solar panels. The thin-layer cells allow 20% of the light into the interior and can generate enough electric power to charge cell phones, for example.
The light-gray tailgate is made from lightweight Lexan polycarbonate, allowing a view of the aluminum structure and vehicle interior. “Aerodynamically optimized” 20-in wheels are fitted with low-friction tires.