Experimental determination of heat generation rates of lithium-ion batteries by thermal protection method

Abstract

Experimental determination of heat generation rates is crucial in the thermal safety design of automotive batteries. A thermal protection method (TPM) is proposed to determine the heat generation rates of 18650 cylindrical lithium-ion batteries under different discharge rates. The physical model based on the thermal protection method is established, and its feasibility is demonstrated through theoretical analysis. In the experimental setup, by introducing lateral thermal protection batteries (TPB) to minimize the heat loss of the center test battery (CTB), heat generation rates of the battery can be obtained based on the temperature change of the CTB. The average heat generation rates of the battery at 1, 2, and 3 C discharge rates are found to be 0.255, 0.844, and 1.811 W, respectively, which can be quadratically correlated with the discharge rate. In addition, a benchmark test of the present measurement against the commonly used accelerating rate calorimeter (ARC) was conducted. Relatively small deviations of 3.77%, 4.20%, and 1.09% were identified in the heat generation rates for the discharge rates at 1, 2, and 3 C. In comparison with the ARC equipment, the present TPM can be more representative of the transient battery heat generation characteristics with a much shorter time for thermal equalization. Finally, to further verify the accuracy of the present method, standard samples of the same size as the actual battery were made, which were capable of controlling heat generation through a direct current power supply. A comparison of the heat inputs of the standard sample with the heat generation rates measured by the thermal protection method shows a relative deviation of 1.01% maximum. With high measurement accuracy and an easy-to-build experimental setup, the proposed method has promising prospects in automotive applications.