Current mass-produced hybrid cars use nickel-metal hydride batteries, but Mercedes-Benz says it will launch the first hybrid with lithium ion batteries. Lithium ion batteries are more efficient than nickel-metal hydride batteries and have a better weight-to-power ratio, and are used in the all-electric Tesla roadster as well as in many plug-in hybrid conversions. But large stacks of lithium ion batteries can overheat, a serious problem in an automotive application. Mercedes-Benz announced it has 25 patents around making lithium ion suitable for cars, detailing a key breakthrough of integrating the battery with a car's climate control system, which maintains the battery temperature at between 60 degrees and 95 degrees Fahrenheit. In this temperature range, lithium ion batteries offer optimal performance and long life.
Mercedes-Benz will first use lithium ion batteries in its S400 BlueHybrid, launching in 2009. The S400, unveiled at the 2007 Frankfurt auto show, will use a 3.5-liter V-6 engine complemented by the hybrid system. Mercedes-Benz claims 30 mpg for the S400 and a 0 to 62 mph time of 7.3 seconds with its 300 horsepower.