A method for interrupting an inflow current of a battery system, the battery system including: a plurality of stacked prismatic battery cells, forming a battery block, each having a sealing plate provided with electrode terminals that are positive and negative; parallel-connected bus bars each connected to the electrode terminals of the prismatic battery cells and connecting some or all of the plurality of prismatic battery cells in parallel; and a safety mechanism configured to be capable of interrupting a current path of the prismatic battery cells connected in parallel by the parallel-connected bus bars, the method comprising: configuring the sealing plate of each of the prismatic battery cells to comprise a metal sheet and to convexly deform due to a rise in an internal pressure due to an internal short circuit of the each of the prismatic battery cells; bringing the sealing plate of one of the prismatic battery cells that has convexly deformed into contact with the parallel-connected bus bars to form external short circuitry between the electrode terminals that are positive and negative of corresponding one of the prismatic battery cells connected in parallel to the one of the prismatic battery cells comprising the internal short circuit; and the external short circuitry activating the safety mechanism that interrupts a current flowing into the one of the prismatic battery cells comprising the internal short circuit, characterized in that, the method further comprises the steps of:- providing the prismatic battery cells to comprise a top cover disposed at a fixed position, being a position facing a side opposite to surfaces of the parallel-connected bus bars, the surfaces facing the sealing plate, and, configuring the parallel-connected bus bars to press against the sealing plate, by means of the top cover in contact with the parallel-connected bus bars pushed out by the sealing plate that has convexly deformed, and thereby arranging the parallel-connected bus bars to be short-circuited via the sealing plate. a plurality of stacked prismatic battery cells, forming a battery block, each having a sealing plate provided with electrode terminals that are positive and negative; parallel-connected bus bars each connected to the electrode terminals of the prismatic battery cells and connecting some or all of the plurality of prismatic battery cells in parallel; and a safety mechanism configured to be capable of interrupting a current path of the prismatic battery cells connected in parallel by the parallel-connected bus bars, the method comprising: configuring the sealing plate of each of the prismatic battery cells to comprise a metal sheet and to convexly deform due to a rise in an internal pressure due to an internal short circuit of the each of the prismatic battery cells; bringing the sealing plate of one of the prismatic battery cells that has convexly deformed into contact with the parallel-connected bus bars to form external short circuitry between the electrode terminals that are positive and negative of corresponding one of the prismatic battery cells connected in parallel to the one of the prismatic battery cells comprising the internal short circuit; and the external short circuitry activating the safety mechanism that interrupts a current flowing into the one of the prismatic battery cells comprising the internal short circuit, configuring the sealing plate of each of the prismatic battery cells to comprise a metal sheet and to convexly deform due to a rise in an internal pressure due to an internal short circuit of the each of the prismatic battery cells; bringing the sealing plate of one of the prismatic battery cells that has convexly deformed into contact with the parallel-connected bus bars to form external short circuitry between the electrode terminals that are positive and negative of corresponding one of the prismatic battery cells connected in parallel to the one of the prismatic battery cells comprising the internal short circuit; and the external short circuitry activating the safety mechanism that interrupts a current flowing into the one of the prismatic battery cells comprising the internal short circuit, providing the prismatic battery cells to comprise a top cover disposed at a fixed position, being a position facing a side opposite to surfaces of the parallel-connected bus bars, the surfaces facing the sealing plate, and, configuring the parallel-connected bus bars to press against the sealing plate, by means of the top cover in contact with the parallel-connected bus bars pushed out by the sealing plate that has convexly deformed, and thereby arranging the parallel-connected bus bars to be short-circuited via the sealing plate.