Effect of Electrical Connection on Thermal Propagation of Parallel Battery Module

Electrical connection plays an important role in not only direct heat transfer, but also the transmission of electric energy and the transformation of electrothermal effect in the parallel battery modules. The thermal propagation simulation research model was established based on the equivalent circuit and thermal runaway experimental research of a module formed by four parallel cells, which superimposes the discharge process and corresponding electrothermal effect in the process of thermal runaway and thermal propagation, and pays attention to the SoC (state of charge) state and corresponding thermal runaway energy release changes after cell discharged. Thermal runaway and propagation characteristics of parallel and non-parallel battery modules were analyzed and results showed that without considering the energy exchange between the system and the environment, the parallel battery module will accelerate the process of thermal propagation. Further analysis shows that the relationship between the stored electric energy and the thermal runaway energy of battery cells is the key factor affecting the thermal propagation rate of parallel battery module. If the slope of the stored electric energy of the cell changing with SoC is greater than the slope of its thermal runaway energy changing with SoC, the parallel circuit will accelerate the thermal propagation process. If the slope of the stored electric energy of the battery changing with SoC is less than the slope of its thermal runaway energy changing with SoC, the parallel circuit will delay the thermal propagation process.