Surrogate models for lithium-ion battery heat generation based on orthogonal experiments by eliminating external wire connection effect

Abstract

• Maximum overestimation of 39.9% in heat generation occurs due to the wire connection at 40 °C and discharge rate of 3C. • Heat generation rate is determined by C-rate, temperature and depth of discharge with ranking order of DR > T > DOD. • Average deviation of 6.90% was obtained between present surrogate model and experimental tests beyond 0.53 W. • Heat generation model of the battery was verified by comparing with experiment measurement under natural convection. In this paper, an experimental investigation on the heat generation rate is presented for the cylindrical lithium-ion batteries under different operation conditions such as changing temperature and depth of discharge by eliminating the external connection effect. The tests were conducted by placing the battery in the thermostat chamber and connecting to the charger instrument through external wires. The intermediate quantities including the overpotential, entropy heat coefficient and internal resistance were obtained by the corresponding orthogonal test in full matrix design. It is found that the maximum overestimation of 39.9% occurs at the highest temperature of 40 °C and discharge rate of 3C with the wire connection. As such, the wire connection effect must be examined and eliminated in the heat generation estimation. The consequent sensitivity analysis indicates that the discharge rate has the largest impact on the heat generation of battery, followed by the temperature and depth of discharge, namely, DR > T > DOD. The temporal heat generating surrogate models of the battery are correlated under different operation conditions with the depth of discharge, temperature, and discharge rate by the response surface analysis, which agrees with experiment results within 6.90% for heat generation rate beyond 0.53 W corresponding to the 1C discharge case. Moreover, the heat generation model is verified by comparing the numerically obtained battery temperature with experiment measurement under natural convection condition. The temporal temperature rise of the battery during actual operation conditions such as worldwide harmonized light vehicles test procedure (WLTP) can be estimated based on the present surrogate models.