A large battery pack of specified voltage and capacity can be assembled from a plurality of identical small cells by dividing the specified capacity by a nominal battery module capacity to determine a desired number of parallel modules to be provided, dividing the nominal battery module capacity by a nominal cell card capacity, to determine the number of cell cards required in each module, connecting the call cards in parallel to a common buswork to form the battery module, and connecting the modules in parallel to obtain the specified battery pack capacity and in series to obtain the specified battery pack voltage