US Patent 8470470 Battery pack manufacturing method, and battery pack

Provided are a battery pack manufacturing method, which can prevent a drawback where some of the used secondary batteries constituting a battery pack prematurely come to an end and which can suppress the enlargement of the temporary voltage difference between a used secondary battery at a charging/discharging time (especially in a low-temperature circumstance), and a battery pack. The battery pack manufacturing method includes an acquiring step of acquiring the individual internal resistances of used secondary batteries collected from the market, a selection step of selecting a plurality of the used secondary batteries having the internal resistances close to each other from a group of the used secondary batteries whose internal resistances have been acquired, and an assembling step of combining the used secondary batteries selected, to constitute the battery pack.