A flowing electrolyte zinc/bromine battery is one of several advanced batteries for electric power storage currently under development by MEIDENSHA and the New Energy Industrial Technology Development Organization(NEDO) sponsored by the Ministry of International Trade and Industry(MITI) in Japan(1). The advantages of this battery include high energy density and an abundant availability of materials, Other features of the zinc/bromine battery include: (1) An aqueous-electrolyte battery operated at ambient temperature and is characterized by easy maintenance control. (2) The battery's conductive carbon- plastic electrode(CP electrode) makes it suitable for large capacity application and for mass production at low cost. (3) With small numbers of components based on simple battery reactions, it is compact and can be assembled easily. We have designed a IMW(4MWh) class battery system for a battery storage test facility at Imajyuku substation of the Kyushu Electric Power Company. This 1MW class battery system is constructed 24, 25kW sub-module batteries in series connection. These batteries are scheduled for installation from June 1990, and the facility will be operation by the end of this year. Before installation, these batteries will be tested by MEIDENSHA. Additionally, we have begun life-cycle test and an accelerated life-cycle testing of 3kW and 0.3kW class battery, respectively. We have indicated that the life of zinc/bromine battery is dependent upon the durability of CP electrode. In an effort to improve this electrode, we have analyzed physical and chemical characteristics of the deteriorated electrode.