A battery assembly includes a plurality of battery modules electrically connected together, each battery module acting as a secondary battery and including an electrode group, an electrolyte, a container for housing the electrode group and the electrolyte, and a safety valve operating in accordance with the internal pressure of the container. The working pressure of each safety valve is set so that the safety valve of at least one battery module is opened when the at least one battery module has its maximum internal pressure or less during the charge equalization. It is possible to provide a battery assembly that can improve the reliability of the container strength by keeping the working pressure of each safety valve lower than the pressure that the container resists even under elevated temperature conditions.