Quasi steady state method to measure thermophysical parameters of cylindrical lithium ion batteries

Abstract The thermophysical parameters such as thermal conductivity and specific heat play a vital part in the thermal design of the power battery pack composed of cylindrical lithium ion battery cells. This work proposes a quasi steady state method with considering heat loss to measure the thermophysical parameters of two classes of 21700 and 18650 cylindrical cells, respectively. To this end, the theoretical model and the corresponding measurement method were developed in consideration of the heat loss, and the two cells' thermophysical parameters were experimentally determined over a wide operating temperature range of −20–60 °C. The results show that both of the thermal conductivity and the specific heat of the cells increase linearly with the increase of the operating temperature. In comparison, the cell temperature has a greater influence on the specific heat than that of the thermal conductivity. The experimental verification reveals that the measurement error is behind 5.1%. Having a short measurement time within 930s, the present work provides a fast and convenient solution on determining the thermophysical parameters of the cylindrical cells without resorting to the costly instruments.