Cooling optimization strategy for lithium-ion batteries based on triple-step nonlinear method

In the battery cooling system, the actual heat dissipation demand of the battery varies with the external environment and load current. If the battery does not dissipate heat in time under high current load and excessive increase of the temperature will threat to the safety of battery. In this paper, a cooling optimization strategy for lithium-ion batteries based on triple-step nonlinear method is proposed. Firstly, a lumped thermal model for lithium-ion batteries under liquid cooling considering the change of heat transfer coefficient with coolant flow rate was established. Then the accuracy of the lumped thermal model was verified by comparing with the battery model in AMESim. Based on the nonlinear and time-varying characteristics of lumped thermal model, a triple-step nonlinear cooling optimization algorithm is presented and its stability and robustness are proved. The triple-step nonlinear method and PID method are compared under different operating conditions, the simulation results show that the triplestep nonlinear method ensures that the operating temperature of the battery is lower than 305 K and the deviation from the target temperature is lower than 2.0 K, it also improves the speed and stability of the cooling process of lithium-ion batteries. (C) 2020 Elsevier Ltd. All rights reserved.