belt running off the engine, in addition to the cost of a compact electric motor and specialized microprocessors to control energy flow to the motor, GM eventually decided to price the Volt at a base price from around US$40,000. The US$1 billion cost to develop the Volt is equivalent to creating three vehicles on an existing platform. First generation (2010–2015) Production model The production design model officially unveiled on September 16, 2008, as part of General Motors (GM) centennial celebration at the Wintergarden headquarters in Detroit. The production model differed greatly in design from the original concept car. The carmaker cited necessary aerodynamic changes needed to reduce the concept car's high drag coefficient of down to , still higher than the Toyota Prius . Another reason was the use of General Motors's new global compact vehicle platform Delta II to keep costs reasonable, and shared with the 2010 model year Chevrolet Cruze. Another significant difference from the concept car is the seating, as the production Volt seats four rather than five passengers. This change was due to the higher-than-usual central tunnel that runs from the front console to the rear seat that houses the car's T-shaped battery pack. After the concept was put into the pipeline for production, GM began looking for a partner to develop the Volt's lithium-ion battery pack. The carmaker evaluated about 25 battery cell chemistries and constructions from around two dozen lithium-ion battery makers around the world. Due to their more promising cell technologies, two companies were selected in June 2007, Compact Power (CPI), which uses a lithium manganese oxide (LiMn2O4) cell made by its parent company, LG Chemical; and Continental Automotive Systems, which uses lithium iron phosphate based cylindrical cells made by A123Systems. By the end of October 2007 CPI (LG Chem) delivered their finished battery pack prototypes, and A123 delivered theirs by January 2008. GM's testing process was conducted at the laboratory the carmaker had created for the GM EV1 program. The battery packs included monitoring systems designed to keep the batteries cool and operating at optimum capacity despite a wide range of ambient temperatures. To ensure the battery pack would last 10 years and expected for the battery warranty, the Volt team decided to use only half of the 16 capacity to reduce the rate of capacity degradation, limiting the state of charge (SOC) up to 80% of capacity and never depleting the