BMW told us that they developed the mild hybrid system to avoid some of the trade-offs inherent in other other systems. Among those are a significant loss of cargo space due the need to package the battery. In the case of the 7, the use of a new lithium ion battery has allowed the engineers to stuff it into a corner of the trunk. The hybrid only sacrifices 1.4 cubic feet of volume and reportedly can still accommodate four standard golf bags. The smaller battery only adds 62 pounds over the rear axle. Nice Car's:2011 BMW ActiveHybrid 7

According to BMW, the point of the mild hybrid system was to create a balance between performance, weight and efficiency. A typical strong hybrid system adds about 300-400 pounds on to the mass of the base vehicle, much of it attributable to the battery pack as well as the complex power-split transmission. The mild hybrid 7 weighs just 165 pounds more than a 750i. We had a chance to take a short drive around downtown Los Angeles in an ActiveHybrid 7 and you can read about it after the jump.