Experimental study on thermal runaway characteristic parameters of parallel battery modules

This work introduces a method for measuring the main physical quantities, such as short-circuit current and capacity loss, in the thermal runaway process of the parallel battery module and presents detailed analysis and discussion on a 25 Ah commercial prismatic lithium-ion ferrous phosphate (LFP) battery. By establishing a basic circuit model of the thermal runaway process of the parallel battery module, experiments were conducted to observe the thermal runaway process of the parallel battery module. The parameters related to the electrothermal effect in the thermal runaway process were obtained by either direct measurement or calculation. The results showed that the short-circuit resistance of the cell, which was triggered to thermal runaway changed dramatically. The minimum resistance was about 0.5 mΩ, and the peak current of discharge was more than 1100 A. During the stable discharge process of the other parallel cells to the thermal runaway cell, the short-circuit resistance was about 10 mΩ. In the stable discharge stage, the electric heating power was about 600 to 900 W. However, the power of thermal runaway reaction from the cell itself was still more than 30 times the heating power of the electrothermal effect, exceeding 21 kW. The accuracy of the measurement method and analysis method was also verified by comparing the same parametric data obtained using different methods. The results showed that the method is feasible for studies on the mechanism and simulation of thermal runaway of parallel battery modules.