Film-covered battery and assembled battery

An assembled battery, comprising

• a plurality of unit batteries connected in series or parallel and stacked one upon another, wherein each of the unit batteries comprises a battery element and a covering film
• wherein the covering film covers the battery element and is sealed by heat fusion on a periphery of the covering film,
• an inter-terminal seal portion is formed between a positive electrode terminal and a negative electrode terminal, said inter-terminal seal portion is larger than that of any other seal portion;
• wherein the positive electrode terminal and the negative electrode terminal are located on the same side;
• a safety valve is located at a portion other than the inter-terminal seal portion and is not in contact with the surface of the covering film of an adjoining unit battery;
• wherein an internal pressure of said inter-terminal seal portion is released by the safety valve;
• wherein each of the unit batteries have a heat-resistant retaining member, said heat resistant retaining member is located on the outer surface of the inter-terminal seal portion and adapted to be in contact with the cover film of the adjoining unit battery, and the heat-resistant retaining member is a rectangular or circular column shape having a height equal to the height of the unit battery minus the thickness of the inter-terminal sealed portion.