Battery Batch Impedance Analysis for Pack Design

The impedance of four different battery cell model batches have been measured and analyzed. Impedance have been measured at four frequencies and at three states of charger. Various statistical methods have been used to analyze measurement results and provide insight in impedance variation and distribution characteristics. A separate correlation analysis between impedance and nominal capacity has been carried out. Such correlation information can significantly improve battery testing speed and performance estimation. The obtained measurement results are useful for further battery model development - to introduce manufacturing variance as well as for the development of cell sorting methodology which is performed prior to battery pack assembly.