BMW builds luxury hybrid sedan

BMW announced the Concept 7-series ActiveHybrid, a mild hybrid based on its 7-series sedan.

Wayne Cunningham Managing Editor / Roadshow
Wayne Cunningham reviews cars and writes about automotive technology for CNET's Roadshow. Prior to the automotive beat, he covered spyware, Web building technologies, and computer hardware. He began covering technology and the Web in 1994 as an editor of The Net magazine.
Wayne Cunningham
2 min read

BMW Concept 7-series ActiveHybrid
BMW's 7-series concept uses a mild hybrid powertrain. BMW

Following on the recent announcement by Mercedes-Benz of its mild hybrid sedan with lithium ion batteries, BMW announced its own mild hybrid sedan with lithium ion batteries.

Although it may sound like cutthroat competition, it's more conspiracy, as Daimler and BMW co-developed their hybrid components. And where Mercedes-Benz announced a production car, BMW is still at the concept stage with its Concept 7-series ActiveHybrid. But in keeping with its sport aspirations, the BMW shows no compromise in power, using a twin-turbo V-8 assisted by the mild hybrid system. The twin-turbo V-8 delivers 407 horsepower and 442 pound-feet of torque, while the hybrid system's electric motor, integrated into the transmission, adds 20 horsepower and 155 pound-feet of torque.

BMW Concept 7-series ActiveHybrid engine
The hybrid system was co-developed by Daimler and BMW. BMW

As a mild hybrid, the Concept 7-series ActiveHybrid can't run under electric power alone--the electric motor merely adds thrust when needed and is an essential part of the idle-stop system. At a traffic light, the engine shuts down to save gas, with the electric motor cranking it back up when the driver hits the gas, and adding its power to make up for the initial shortcoming of the engine. BMW claims a 15 percent improvement in fuel economy.

The lithium ion battery pack sits over the rear axle, and gets recharged through regenerative braking. Along with providing electricity for the motor, this battery pack works as a 120 volt power source for the car's onboard electronics.

BMW has previously shown the X6 ActiveHybrid concept, an SUV using a full hybrid system based on technology co-developed by BMW, Daimler, and GM. We first saw a version of that hybrid system in the GMC Yukon Hybrid. BMW promises two cars using some form of its hybrid technology will reach production in 2009. The company might want to hurry up, as Lexus already dominates the segment for powerful luxury hybrid sedans with the LS 600h.

BMW ActiveHybrid diagram
The electric motor is integrated with the transmission. BMW