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 voltageProtection circuitry can be implemented at the module level, by disconnecting one or more modules or the entire battery pack if a fault at the module level is identified; at the cell card level, by disconnecting a cell card if a cell within it is determined to be faulty; and/or internally, in each cell.