Mercedes Hybrid Cars

The Mercedes-Benz S-class gains its first-ever hybrid power train, a clear indication that its maker is shifting from a strict diesel approach to efficiency and finally acknowledging the worth of hybrids as an essential step on the path to electric propulsion. What's more, the Mercedes S400 Hybrid is the world's first production hybrid automobile using lithium-ion batteries (the Tesla Roadster is powered solely by Li-ion batteries). Hybrid propulsion systems aren't anything new, of course, but they're still rare in the luxury class, where the Lexus LS600hL has been standing alone for the past two years. (Courtesy www.automobilemag.com)

The Mercedes-Benz S400 BlueHybrid's propulsion system prioritizes low emissions and high fuel efficiency over powerful acceleration. Essentially a scaled-up version of Honda's Integrated Motor Assist, this new Mercedes powertrain teams a 3.5-liter Atkinson-cycle V-6 with a compact AC motor-generator bolted securely to the crankshaft and a ZF seven-speed automatic transmission. The ring-shaped motor-generator is nearly a foot in diameter but less than two inches thick. The Atkinson cycle, a common hybrid technology, uses late closing intake valves to stretch the expansion (power) stroke for utmost efficiency. While some torque is sacrificed with this approach, the S400's electric motor supplies up to 118 lb-ft to more than cover that loss. The S-class's most notable distinction is the hybrid world's first lithium-ion battery system. Thirty-three cylindrical cells supplied by the French firm Saft are housed in steel container mounted under the hood. (The Tesla Roadster is powered solely by lithium-ion batteries with a similar, but smaller, cylindrical configuration.)

(Courtesy www.automobilemag.com)