Identifying Faulty Electrical Contact Points in Li-Ion Battery Packs

Abstract

The cell-to-cell electrical contact resistance was investigated to estimate the effect of faulty electrical contact point(FECP) on the performance of battery packs. The temperature of the FECP in series circuit rises instantaneously compared to that of other normal points after the start of the current load, but the temperature of the FECP in parallel circuit rises just after the voltage turning point at the end of the charging/discharging process. The voltage difference between the highest voltage and the lowest voltage of the cells at the end of discharge stage increases apparently while the battery pack contains the FECPs, which is a typical feature during the decay of battery packs. In this study, the capacity retention of LiFePO4/C battery at room temperature reaches to 80% after 1260 cycles for a 1p3s pack, 1210 cycles for a 3p3s pack and 1510 cycles for a single cell, in which the average cell-to-cell connector impedance is 0.13 mΩ in the circuit. By contrast, the cyclic charge-discharge stops at 381st cycle for a 1p3s pack with a FECP(0.42 mΩ) in series circuit and at 1097th cycle for a 3p3s pack with a FECP(0.41 mΩ) in parallel circuit.