A Measuring Method of Available Capacity of Li-Ion Series Battery Pack

The Li-Ion battery packs are consist of multiple cells in series and parallel to meet the energy and voltage requirement for high power applications, such as electric vehicle and hybrid electric vehicle. But because of the different consistency between the battery cells, the performance will decline in different levels after a certain charge-discharge cycles. A measuring method of available capacity is proposed in this paper, in order to keep the batteries in series consistent. The available capacity of battery in series is determined by the first cell reaching the upper limit voltage in charging and the first cell reaching the bottom limit voltage in discharging. A total of 4 packs fresh cells are used for implementation of the proposed process.