Patent ID: 7088075

Claim:
A battery pack comprising: a battery block that houses one or more cylindrical lithium ion secondary batteries in a battery package, said batteries being arranged in the battery block according to a given polarity and include an external connector and connected to each other with a metal tab, wherein the tab is made by punching out a metal plate material into a strip shape and bending the strip in a given shape; a circuit block housing a circuit in a circuit package, the circuit having a measurement function associated with at least one of a use condition of the batteries, a measurement function associated with performance of the batteries, and a protection function to protect the batteries, wherein the circuit block housing includes a pressure release hole; and an outer case capable of fitting in and housing the battery block and the circuit block, wherein the battery block and the circuit block can be independently removed and replaced from the outer case, and wherein an inside dimension of the outer case substantially equals a total outside dimension of the battery block and the circuit block, wherein the battery block has a connection terminal on a side facing the circuit block, said connection terminal connected to the tab, and the circuit block has a connection on a side facing the battery block and a part of the connection terminal which is exposed out of the battery package and circuit package includes a blade spring in a tranche shape, wherein at least one of the battery package and the circuit package includes a hermetic package, and wherein the hermetic package has a hermetic structure that is formed by fitting together an open top lower package and an upper package having a groove corresponding to an opening of the lower package by press fitting and the outer case can include a notch on a sidewall of the lower case and a notch on a sidewall of the upper case, wherein the upper case can releasably engage the lower case such that the external connector of the battery block is accessible through the notch.