"Mercedes-Benz Talks Batteries, Hybrid and EV Plans" Green Car Advisor

Mercedes-Benz Talks Batteries, Hybrid and EV Plans

By Robert E. Calem, Contributor New York -- Mercedes-Benz is preparing to transform its flagship S-Class sedan into an "economy" car offering gas mileage comparable to that of the Honda Accord, and that will be only the beginning of the car's fuel consumption makeover, the company promises.

The key change: incorporating a new lithium-ion battery that Mercedes-Benz parent Daimler AG has been developing since the early 1990s.

Due largely to technology advances achieved in the last six years, Mercedes-Benz engineers say, the battery is now ready for mass production and will be used first in the S400 BlueHybrid , a new gasoline-electric S-Class sedan slated to go on sale after the summer of 2009.

The following year, the battery is to be used in a diesel-electric hybrid version, the S300 BlueTec Hybrid, and after 2010 in the more powerful S400 BlueTec Hybrid.

It's a First

Moreover, according to Mercedes-Benz, its projected on-sale date will make the S400 BlueHybrid the first series-production car ever to use a lithium-ion battery in its powertrain.

To learn more about this new battery and the company’s plans for it, Green Car Advisor met with Mercedes-Benz’s Thomas Weber, head of research and development, and Herbert Kohler, chief environment officer, at the New York International Auto Show last week.

While the development work led to a total of 25 new patents for Daimler, Weber noted, the biggest breakthroughs were in solving potential overheating and safety problems.

To deal with the temperature issue, Mercedes-Benz is tying the battery to the vehicle’s air-conditioning system, which will keep it constantly in a range of 59 to 95 degrees Fahrenheit, regardless of the outside environment.

Slogging Through Sand and Snow

According to Mercedes-Benz, this is the ideal temperature range to ensure the battery’s peak performance and long life. The solution of maintaining it with the air-conditioning system was tested for two years in California summers and Swedish winters, in ambient temperatures ranging as low as 50 degrees below zero Fahrenheit, Kohler noted. The battery is expected to carry an eight-year warranty, Weber added.

A battery cell monitoring system makes this lithium-ion battery as safe as any car battery used today, Weber said, adding that a problem or an accident will cause it to shut off.

The company won't disclose which of several competing lithium chemistries is being used, but its supplier, Johnson Controls-Saft and Continental AG, has been working with lithium manganese batteries for the Chevrolet Volt extended range EV.

Small, but Strong

Another important development was this battery’s compact dimensions compared with the nickel-metal-hydride batteries used in the hybrid vehicles sold today, such as the Toyota Prius or Lexus LS 600h.

Like any lithium-ion battery, it also offers higher energy density, better charging efficiency, longer life and greater reliability than a nickel-metal-hydride battery.

Because the battery is already considered commercially viable, Weber said, Daimler is already considering its future applications beyond the S-Class.

Mercedes-Benz is planning to begin testing the batteries by the end of the decade in a fleet of 80 or so Smart Fortwo city cars converted to all-electric drive.

299 Powerful Ponies

The first vehicle to incorporate it, the S400 BlueHYBRID pairs the new battery with a 279-horsepower 3.5-liter V6 gasoline engine and a 20-hp electric motor, for a combined 299 hp.

The electric motor's powerful torque will help it accelerate quickly – from zero to 62 miles per hour in 7.3 seconds, Mercedes-Benz promises – and reach an electronically limited top speed of 155 miles per hour.

Even more significant is the car’s projected average fuel economy rating of 29.7 miles per gallons and its CO₂ emissions of 190 grams per kilometer (Mercedes-Benz’s figures).

In comparison, the EPA fuel economy ratings for a 2008 Honda Accord with a four-cylinder gasoline engine are 22 mpg city and 31 mpg highway. Meanwhile, the 2008 Mercedes-Benz S550 with a V8 engine is EPA rated at 14-mpg city and 21-mpg highway. And the best current model-year S-Class sold anywhere in the world emits 199 grams of CO₂ per kilometer, according to Mercedes-Benz.

The S300 BlueTec Hybrid, set to debut in 2010, will pair Daimler’s lithium-ion battery with a new four-cylinder diesel engine and electric motor delivering a combined 224 horsepower and 0-62-mph acceleration in 8.4 seconds. Its average fuel economy and CO₂ emissions will be 43.4 mpg and 142 grams per kilometer, respectively, Mercedes-Benz says.

Later, the S400 BlueTec Hybrid will pair the battery with a V6 diesel engine and electric motor delivering a combined 265 horsepower and 0-62 mph acceleration in 7.3 seconds. The company expects its average fuel economy and CO_² emissions will be 40.6 mpg and 154 grams per kilometer, respectively.

In addition, Weber said Daimler could incorporate the new battery in a limited-production B-Class fuel-cell vehicle that is scheduled to be available in 2010 if costs of the various components can be brought down.