Method for evaluating laser welding quality of battery module based on coupling model

Since the existing commonly used welding quality detection techniques cannot effectively detect pseudo welding (PW) defects in the laser welding of a battery module, in this study, we first study a one-dimensional heat transfer model of the PW defects of welding spot. Then, we establish an electro-thermal coupling model of a lithium-ion battery (LIB) module. The voltage of the LIB with and without PW is simulated and analyzed. The influence of charge–discharge rates, and geometric shape of welding spot on the battery voltage is discussed in detail. The simulation results show that at the discharge rates of 5 C, 10 C and 15 C, the voltage of PW battery in the discharge stage is about 12 mV, 15 mV and 20 mV lower than that of the normal one respectively. And the effect of the geometric shape of welding spot on the battery voltage is negligible. Based on experimental data of discharge stage, the complete charge–discharge data are calculated using the electro-thermal coupling model, and the voltage Euclidean distance (VED) is proposed. The experimental results prove that the laser welding quality of module can be quickly and accurately detected based on the electro-thermal coupling model and solving the VED.