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MERCEDES IS on an interesting path to future propulsion. And, indeed, judging by the company’s 2012 Paris Auto Show introduction of its B-Class Electric Drive, the future is as near as 2014. What’s more, it’s not completely focused on BEVs (as in “battery electric vehicles”). The Mercedes approach with its B-Class has been to design a basic platform that’ll accept everything from gasoline or diesel or natural-gas internal combustion to hydrogen fuel cells.
The basic structure is a lightweight 4-door hatchback featuring front-wheel drive, the latter chosen for maximizing passenger and cargo space. Clever aspects of design arise in devising the means of spinning the front wheels.
Let’s start with the traditional option, one that continues to offer genuine benefits. A gasoline (or diesel or natural-gas) engine/gearbox assembly is mounted transversely up front. Its fuel tank resides securely toward the rear of the car. These days, catalytically controlled internal combustion is so clean that, depending on one’s source of electric power (e.g., coal), an electric vehicle might be environmentally inferior on a well-to-wheel basis. And that gasoline tank, so easily refilled, is an amazingly inexpensive means of energy storage.
A second option with the same basic platform was called the B-Class E-Cell Plus. This was a plug-in series hybrid (think Chevrolet Volt), its gasoline engine dedicated to running a generator providing extended range for its electric propulsion. The propulsion hardware was up front, the battery pack and gasoline tank residing beneath the cabin.
All this is in the past tense, as the latest word from Stuttgart is that the E-Cell Plus concept, not to say the nomenclature, has been shelved in favor of a pure BEV. The advantage of the E-Cell Plus concept: electric propulsion with a relatively small battery pack and no range anxiety. The crucial tradeoff: complexity of hardware.
The B-Class Electric Drive profits from the Silicon Valley wizardry of Tesla, which appears to have cracked the code of enhanced BEV range. Mercedes claims the B-Class Electric Drive has “attractive driving dynamics over a range of 200 kilometers.” That’s 124 miles, though it’s too soon to know the EPA’s range assessment. The Electric Drive’s motor, battery pack and power control electronics are all Testa-developed. Again, propulsion hardware is up front, energy storage (in a substantially larger and more pricey battery pack) resides beneath the cabin. Mercedes says the B-Class Electric Drive will enter production in 2014.
As its most futuristic offering, Mercedes has said it’ll bring hydrogen power to production in 2014 with its F-Cell, a fuel cell car on this same B-Class platform. The electric motor and power electronics reside up front. The fuel cell stack transforming hydrogen and air into electricity is located beneath the front of the passenger compartment. A trio of hydrogen tanks fit aft of this. Still farther aft, there’s a small battery pack (essentially a buffer to the fuel cell’s output).
Hardly a simple bit of packaging. But the F-Cell’s efficiency is about twice that of internal combustion. Unlike even “quick charge” EV schemes, its hydrogen refill time is comparable to that of traditional fuels. And, in a very real sense, it’s an EV that makes its own E. ds