2015 BMW i8 Battery Pack Dictated Its Entire Design
We’ve finally driven the production 2015 BMW i8 plug-in hybrid sports car, and we came away highly impressed. But one thing stuck out: The car’s size. As it turns out, the i8’s footprint is no accident.
The BMW i8 is literally engineered around its battery pack, which is about the size and shape of a tipped-over grandfather clock. To achieve the i8’s targeted 22-mile electric-driving range, BMW assembles 96 Samsung-supplied prismatic lithium-ion battery cells into a 57.5 x 14.4 x 13.0-inch die-cast aluminum box.
Even though the battery pack’s total energy capacity is 7.1 kWh, normal usage is limited to 5.2 kWh to ensure a satisfactory service life. To guard the 216-pound pack against impact damage and to make it readily removable for service, it—and its aluminum box—runs lengthwise down the middle of the car. It could be only so wide and so tall to avoid overwhelming the interior, so as a result, it became very long to provide the desired energy capacity and maintain ample space for people. […]