Most of the Volt initial design parameters defined for the development of the concept car, then referred as the "iCar" in homage to the iPod, were kept throughout the process up to the final production version. A key design parameter was a target of 40 miles (64 km) for the all-electric range, selected to keep the battery size small and lower costs, and mainly because research showed that in the U. S. 78 percent of daily commuters travel 40 miles or less. This target range would allow most travel to be accomplished electrically driven and the assumption was made that charging will take place at home overnight. This requirement translated using a lithium-ion battery pack with an energy storage capacity of 16 kWh considering that the battery would be used until the state of charge (SOC) of the battery reached 30%. This limit to the SOC was necessary in order to maintain operational performance under a wide range of environments, and to minimize the battery degradation to allow at least a ten-year life span. The initial target range for the gasoline engine/generator was set between 250 to 300 miles (400 to 480 km) and the vehicle had to be family size for four or five passengers.