PURPOSE: To prevent battery efficiency from worsening by preventing a leak current flowing through a manifold during waiting for a discharge in a zinc- bromine battery for performing a charge/discharge by circulating an electrolyte in a cell stack formed by plurally laminating alternately an electrode plate and separator plate.

CONSTITUTION: In upper side both end parts of a frame of each electrode plate and separator plate in a cell stack 2, electrolyte inlet/outlet manifolds 4a, 4b are provided. In an opposite side to inlet/outlet side pipes 3a, 3b, a bypass pipe 7 for connecting the manifolds 4a, 4b is provided. In the case of stopping operating a pump 5 during waiting for a discharge, by infiltrating air from a small hole 6 to pass through the electrolyte outlet manifold 4b, bypass pipe 7 and the electrolyte inlet manifold 4a, an electrolyte in the manifolds 4a, 4b of the cell stack 2 is returned back to a tank 1.