Patent ID: 8252455

Claim:
A battery pack comprising a plurality of secondary batteries and a bus bar connecting the secondary batteries, each secondary battery comprising a cylindrical battery case, a positive and negative electrode body group housed in the battery case, and first and second terminal plates located on both ends of the battery case and connected to first and second electrode bodies of the electrode body group respectively, wherein the secondary battery further includes: a current collector placed on an end of the electrode body group on the first terminal plate side, the current collector being connected to the first electrode body of the electrode body group; and an insulating member placed between the first terminal plate and the current collector, the first terminal plate is partly formed with a thin portion, the insulating member is formed with a through portion in a position corresponding to the thin portion of the first terminal plate, a portion of the current collector placed in a position corresponding to the thin portion of the first terminal plate is in contact with the thin portion of the first terminal plate through the through portion of the insulating member, the thin portion of the first terminal plate is configured to be deformed outward when internal pressure of the battery rises, thereby breaking electric connection between the first terminal plate and the current collector, the bus bar is placed so that a portion of the bus bar connected to the first terminal plate of the secondary battery covers a portion of the first terminal plate other than the thin portion, the electrode body group is a hollow wound body including the first and second electrode bodies wound in overlapping relation with a central portion being hollow, and the current collector and the insulating member are formed with through holes communicated with the hollow portion of the hollow wound body.