Mercedes "Breakthrough" Battery Developer Also GM Volt Supplier
March 03, 2008

By Bill Visnic

Our editor in Geneva, Switzerland, says this week's international auto show there is buzzing about Daimler AG’s reputed breakthrough in the development of lithium-ion batteries for hybrid-vehicle applications.

Daimler’s Mercedes-Benz unit is claiming the “first patented integration of a lithium-ion battery into a series-produced passenger car” when it launches the Mercedes-Benz S400 BlueHYBRID starting in 2009.

Mercedes’ 2009 rollout, in effect, trumps the earliest-known planned deployment of lithium-ion for production vehicles, believed to be General Motors Corp. for its own hybrid applications in 2010, and Toyota Motor Corp, also sometime in the 2010 timeframe. GM, of course, most famously promises its own lithium-ion battery breakthrough for its highly promoted Volt “extended-range” electric vehicle (E-REV), which also is earmarked for introduction around 2010.

Mercedes’ new lithium-ion batteries are supplied, perhaps not coincidentally, by Continental AG — one of two suppliers contracted by GM to develop the lithium-ion formula for the battery pack of Volt’s E-Flex architecture. For the Volt contract, Continental is integrating the lithium-ion technology of A123 Systems of Watertown, Massachusetts. (The other supplier tasked with developing lithium-ion for the Volt is Michigan’s Compact Power Inc.)

Continental said in a release it will begin making the S400 Bluetec HYBRID batteries by the end of this year.

The Mercedes and Continental announcements make it clear lithium-ion battery chemistry apparently is ready for “mild” hybrid applications that rely on electric power to propel a vehicle only for short distances and low speeds, if at all. It is the much higher power demands of next-generation “full” and plug-in hybrids — such as the Volt and Toyota’s proposed plug-in Prius  — that have challenged lithium-ion battery developers.

Lithium-ion batteries for plug-in hybrids — or E-REVs, as GM prefers to call the Volt — must deliver substantially more energy-storage capacity than mild-hybrid applications, and satisfy drastically more-demanding performance requirements.

A Mercedes news release said the S400 BlueHYBRID application leverages 25 patents, including an important detail: The lithium-ion battery is “integrated” into the vehicle’s climate control system in order to keep the battery pack in the correct temperature range for optimal performance. It is known that extreme cold, for example — but not temperatures uncommon in parts of the U.S. and Europe — can severely restrict the performance of lithium-ion chemistry.

Mercedes says the volumetric energy density of its new lithium-ion battery is 1.9 kW per liter, but it remains to be seen how this compares with competing lithium-ion technology, as battery-energy density — how much power can be stored in relation to size or weight — more often is stated in terms of watt-hours per kilogram.

In addition to the lithium-ion batteries, Continental said in a release it also supplies the S400 BlueHYBRID’s power inverter and DC/DC converter, both critical and high-value components.

The new lithium-ion battery is not limited to the S400 BlueHYRBRID. Mercedes also is showing in Geneva the Vision GLK Bluetec Hybrid — a concept variant of its upcoming GLK compact crossover. The GLK Bluetec Hybrid combines a four-cylinder diesel engine with a small electric motor that provides acceleration boost and other key hybrid functions. The battery pack for this concept car also uses the new lithium-ion technology, Mercedes said.

Photo 1: Mercedes-Benz Vision GLK Bluetec Hybrid (photo courtesy Daimler AG).

Photo 2: Dr. Thomas Weber, Daimler AG member of the board of management responsible for research and development at Mercedes-Benz Cars, with the S 400 BlueHYBRID (photo courtesy Daimler AG).

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