A statistical method for analyzing lifetime of a series-connected battery cells

Abstract

In order to establish a sustainable society, a large variety of secondary batteries are necessary, each of which is a battery pack composed of many battery-cells connected in series and parallel. Such a battery pack must have an optimal connection suitable to its application. However, the optimality cannot be claimed deterministically in the design stage, since the battery behavior heavily depends on the environment of usage and the variability of production. To cope with this situation, we propose a statistical method for analyzing the distribution of lifetime of a battery pack composed of cells connected in series, when aging curve and its distribution of a single cell are given. We also show some experimental results of aging curves of cells and series-connected battery modules to evaluate our method.