Abstract: A battery module and an intermediate module for use together in a stack of modules permit flexible electrical configurations of the stack. The battery module has multiple electrically conductive paths extending between its top and bottom sides; one of the paths is connected in series with the module's cells, while at least one of the other paths acts as a pass-through that allows power or communications to pass through the module. The intermediate module also contains pass-through electrical paths that route power or communications from one battery module on one of the top and bottom sides of the intermediate module to the pass-through path of the battery module on the other of the top and bottoms ides of the intermediate module. This allows the modules in a stack to be electrically connected together in different series-connected groups.