Modular batteries can be widely used in energy storage scenarios, whose performance is deeply determined by cells' different electrical factors. Meanwhile, the effect of individual factors on the maximum capacity of the module varies with the topology of the module. In this paper, six kinds of lithium-ion battery modules composed of six cells, which corresponded to six kinds of typical topologies, were subjected to three factors and two levels of orthogonal test. Then, the influence of battery cell's initial capacity, voltage and internal resistance on module discharge capacity was obtained. Finally, by multivariate linear regression, the impact weight of those electric factors was extracted, which was proved to be reliable by mathematical analysis. In order to study the effects of different factors on battery module, this paper conducted complete experimental design, parameter analysis, law validation and weight extraction process. The results can provide an effective solution for improving the discharge capacity of battery energy storage module.