Mercedes S400 BlueHybrid

European manufacturers have been slow to adopt hybrid-electric technology—in part because half the new cars sold there are diesels, which use less fuel to start with. Now Mercedes-Benz has launched its first production hybrid.

It’s a simple “mild hybrid” that restarts the engine after it’s switched off when stopped, as well as adding some degree of electric boost. But the new car comes with a kicker: The Mercedes-Benz S400 BlueHybrid is the very first production hybrid in the world with a battery that uses lithium ion cells, rather than the less energy-dense nickel-metal-hydride found in every other hybrid thus far.

In Benz-speak, “blue” indicates what we might call a “green” car. (Its current concept for a zero-emissions electric vehicle is called BlueZero.) The S400 BlueHybrid is already on sale in Europe, and planned for the US later this year as a 2010 model. On the European test cycle, it achieves 30 miles per gallon (7.9 liters/100 km)—not bad for a full-size sedan weighing well over 2 tons. Claimed CO2 emissions are 190 g/km.

A 15-kW electric motor between the 275-horsepower 3.5-liter V6 engine and the 7-speed automatic transmission contributes torque under heavy engine loads, restarts the engine, and provides a small amount of electric energy to move the car away from stop—though “not even to 2 or 3 miles per hour,” said Christian Mordieck, the Mercedes-Benz engineer who led battery development for the car.

Cost Concerns

Absent various labels and badges, you’d never know this big Benz sedan is a hybrid. The performance won’t give it away either; the 0-to-100-km/h time of 7.2 seconds is similar to the non-hybrid version. But perhaps discretion is appropriate. Mordieck admits that this first hybrid took some effort to create. “We learned that every day begins with a new challenge,” he said ruefully, describing the process of engineering the company’s first traction battery for a production car.

While the company is proud to claim the first lithium ion hybrid, “the cost is much higher than we would like,” Mordieck says. The company hasn’t yet priced the car for the US, but the premium is expected to be less than US $14,000—on a vehicle that starts at US $88,000.

It’s the battery that most distinguishes the S400. While Toyota built a handful of its Vitz subcompact—we know it as the Yaris—with 4 small lithium ion cells for an idle-stop system several years ago, the big Benz hybrid can claim the first use of lithium ion cells in any series-production hybrid. The pack itself, using cells built in France by JCI-Saft, contains 0.7 kilowatt-hours of energy. Showing the size and mass advantages of lithium ion against earlier nickel-metal-hydride packs, Mercedes-Benz was able to fit the entire pack into the same space (at the right-hand base of the windshield) that previously housed the car’s standard lead-acid 12-Volt starter battery. No changes to the body structure were required. To keep its temperature below 25 degrees C, however, the car’s air-conditioning system had to be plumbed into the pack.

More Benz Hybrids On The Way

The S400 BlueHybrid is far from the only Benz hybrid, however. The company is expected to release a “full hybrid’ version of its US-built ML sport utility that uses the Two-Mode Hybrid system, co-developed with GM, Chrysler, and BMW, by the end of this year as well. This will make the ML one of very few vehicles in the world offered with gasoline, hybrid, and diesel powertrains, since Benz introduced the 50-state ML320 Bluetec late last year.

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