| Lithium-ion batteries are widely used in army combat systems and civil new energy vehicles due to their advantages of high energy density,low self-discharge rate and long cycle life.In extremely cold environments at-30℃,lithium-ion battery impedance increases,peak power and available capacity can drop sharply.This paper proposes the controllable short-circuit fast selfheating technology based on the current thermal effect.The low temperature and electric characteristics,thermal characteristics and safety of the battery are analyzed,which can be safely discharged at a minimum temperature of-45℃,suitable for the use and research at low temperature-30℃.In order to avoid excessive available capacity loss and achieve the purpose of rapid battery preheating.Using DC discharge,the temperature adaptive available capacity decline model was constructed.After the battery per temperature rise of 5℃ and 1000 cycles,the battery available capacity retention rate was maintained at 80% as the available capacity loss threshold,and optimized through the intelligent algorithm.The minimum preheating current value of the battery thermal balance is also calculated.The optimization of the minimum and maximum preheating currents for the subsequent heating strategy is constrained by the boundary conditions.Many physical and chemical processes or features inside the battery are related to temperature,and the thermoelectric coupling characteristics are particularly significant at low temperature.Electrical parameters with the change of current,so the lithium battery electrical characteristic model and the temperature rise model coupling,electrical characteristic model by applying dynamic conditions,simulation output results show that the model estimation voltage and electrical test voltage numerical consistency is good,error within 2%,proved the accuracy of the model and parameters.The thermal model simulates the temperature rise change of the battery,and the various simulation results can be better consistent with the experimental measurements.At the same time for the pursuit of battery fast heating and less battery available capacity decline the two mutual constraints,based on the intelligent algorithm of low temperature internal heating strategy,optimize the current in the minimum and maximum boundary current range,implements the extreme cold temperature of heating time and available capacity loss,can evaluate the impact of the battery after preheating.Finally,based on the proposed heating strategy,the hardware and software parts of the power battery management system are designed,and the preheating function of lithium battery is realized by using the principle of pulse width modulation.The quantitative analysis method of available capacity loss of low temperature heating,thermoelectric coupling model of lithium battery,low temperature optimization heating strategy of lithium ion battery,controllable short circuit hardware and software design.It solves the poor low temperature performance of lithium ion batteries,realizes the effective improvement of low temperature performance of lithium ion batteries,forms a systematic solution for low temperature application of lithium ion batteries,improves the operational reliability of military system,and advantageous supports the promotion and application of electric vehicles. |
