Lithium Ion Battery Safety Management System Based On The Liquid Cooling Strategy

The capacity,internal resistance and voltage of lithium-ion battery are very sensitive to the operating temperature.Therefore,the non-uniformity of the internal temperature of the battery pack can significantly reduce the performance of the battery pack and shorten the battery cycling life.In addition,as the lithium-ion batteries are integrated,the generated heat will accumulate in the battery pack,leading to thermal runaway and cause a fire or explosion.In this paper,the finite element numerical simulation method was used and the small size of the experiment was designed to study the lithium-ion battery management and safety protection technology based on the liquid cooling.And it was proposed the establishment of liquid-cooling integrated system,providing the battery thermal management and firefighting a technical support.The dynamic charge and discharge tests were carried out in the open environment,and the corresponding temperature,voltage and current were studied.The results show that in the open environment dynamic cycle,the current,voltage and temperature of the lithium ion battery were still remained the same changing process in each work step.After the lithium-ion batteries were packed,there was a time difference appeared among the peak of each measurement point,while the extreme temperature and temperature fluctuations increased.The maximum temperature was 27.4 ?,38.5 ? and 62.9 ?,the maximum temperature rise was 8.9 ?,16.3 ?and 37.7 ?,and the maximum temperature difference was 4.9 ?,4.2 ? nd 13.7? in the system at 0.5C,1C and 3C cycle rate,respectively.After using the liquid cooling strategy,the dynamic separation disappeared and thermal balance capacity improved.The maximum temperature was 31.8 ?,38.5 ? and 56.2 ?,and the maximum temperature difference was 1.6 ?,3.5 ? and 29.5 ? in the system at 0.5C,1C and 3C cycle rate,respectively.The dynamic cycling behavior of the single battery and battery pack based on the liquid cooling strategy was studied by experiment and numerical simulation.The results showed that the experimental and simulated single cell temperature distribution was well fitting in the dynamic cycle,but the simulation of the charging voltage value was higher than the experimental,the maximum difference was 0.15V,while the simulation temperature peak in the charging period was wider than the experimental.The simulated temperature distribution trend of the battery pack based on the liquid cooling strategy was similar to that of the experiment.However,the thermophysical and kinetic parameters were the function of temperature,but they were considered constant in the simulation.This resulted in the maximum temperature of the simulated calculation being lower than the experimental,the maximum deviation between simulated temperature and experimental temperature in the system was 1.79 ?,4.44 ? and 23.09 ? at 0.5C,1C and 3C cycle rate,respectively.Except,the simulated temperature value of the outer battery in the system was similar to the experimental,the maximum deviation between simulated temperature and experimental temperature in the system was 1.11 ?,3.09 ? and 7.15 ? at 0.5C,1C and 3C cycle rate,respectively..In this paper,the thermal response behavior of the fire pipe was studied,and the fire extinguishing effect of the fire pipe system was studied as well.According to the thermal runaway behavior and heat transfer process of the battery,the corresponding fire detection system was presented.The results show that the response time of fire pipe was shorter and cooling was more obvious in the flame.When the fire extinguishing system was arranged directly above the battery,the fire is controlled within 5.6 s after the fire.With the increase of the fire extinguishing agent,the temperature of the system can be significantly reduced,preventing the batteries reignition and the chain of thermal runaway.The out of control batteries which were outside the firedetect pipe effective area will continue to heat other batteries,and then trigger a chain of thermal runaway,resulting in fire extinguishing system failure.According to the experimental results,the method of coupling fire fighting with thermal balance strategy was proposed.