BMW ActiveHybrid 7 Series

BMW ActiveHybrid 7 Series

Like many European brands that rely on diesels, BMW has been late to the party in introducing electric-drive cars. That's a risky strategy for North America, where it has had to add incentives on diesels and try to tie them to the Cash-for-Clunkers program.

Now it's making up for lost time, not only with its experimental Mini E electric car but also with production versions of two separate hybrids, to be introduced at the Frankfurt Motor Show next month.

Two hybrid systems: one full, one mild 

The BMW ActiveHybrid X6, shown as a concept back in 2007, is the fruit of its cooperation in the TwoMode Hybrid project with General Motors, Daimler, and Chrysler.

GM offers that system in its full-size 2009 Chevrolet Silverado Hybrid and GMC Sierra Hybrid pickup trucks, as well as various full-size sport utilities including the ultra-luxe 2009 Cadillac Escalade Platinum Hybrid.

The hybrid X6, built in BMW's Spartanburg, South Carolina, plant along with its sibling the X5 sport-utility vehicle, is expected to use a nickel-metal hydride battery pack to provide enough energy to let the hybrid X6 run in electric mode up to 20 or 30 miles per hour.

The Two-Mode system will also be used in the 2010 Mercedes-Benz ML450 Hybrid sport utility, making the Benz ML one of the few vehicles to offer gasoline, diesel, and hybrid variants in the US. The BMW X6 will share that distinction once its hybrid variant goes on sale.

BMW's second hybrid, a BMW 7-Series sedan also tagged ActiveHybrid, is equipped with a different hybrid. This one is a "mild hybrid," which is to say, it can't move the car on electric power alone, as the full hybrid systems in such cars as the 2010 Toyota Prius do.

Small motor, big torque

Instead, the BMW mild hybrid system's 20-horsepower electric motor restarts the 407-horsepower 4.4-liter V8 engine after it shuts off at stops, and adds torque to boost the power available from the engine.

That motor may only have 20 hp, but it can add up to 155 foot-pounds of torque to the 442 foot-pounds from the combustion engine.

The mild hybrid system, which is expected to use the same lithium-ion battery technology as the 2010 Mercedes-Benz S400 BlueHybrid sedan already on sale in Europe, is said to improve gas mileage by about 15 percent.

BMW hasn't announced US plans for either new model,  but hybrids are more popular in the US than in any other market.

In Europe, where diesel fuel is taxed far less than gasoline, diesels now have 50 percent of the new-car market. In the US, by contrast, hybrid cars outsell diesel cars.

2007 BMW X6 ActiveHybrid Concept

2007 BMW X6 ActiveHybrid Concept

[Motor Authority]