Experimental study on the performance of power battery module heating management under a low-temperatures charging scenario

To effectively solve the problem that the capacity of lithium power batteries decreases significantly and is prone to irreversible damage under low-temperature charge and discharge scenarios, which seriously affects the driving range, cycle life and service safety of electric vehicles (EVs). In this paper, a low-temperatures thermal management system of pulsating heat pipes with ethanol as the base fluids and TiO2 nanofluids as the working fluids (TiO2-CLPHP TMS) is constructed. On this basis, the thermal performance analysis of TiO2 nanofluids pulsating heat pipes (TiO2-CLPHP) is carried out under different volume concentrations (0 %, 0.5 %, 1.0 %, 2.0 %, 4.0 %, and 8.0 %) and different fluid filling rates (30 %, 50 %, 70 %, and 90 %) in a low-temperature environment. Aiming at the low-temperatures charging scenario of the battery module, the performance test of the TiO2-CLPHP TMS for the battery module heating management is carried out under different low-temperature environments (-5 degrees C, -15 degrees C, and -25 degrees C) and different charging rates (0.3C, 0.5C, 0.7C, and 1.0C). The experimental results show that TiO2-CLPHP with fluids filling rate of 50.00 % and TiO2 nanofluids concentration of 2.00 % has good performance in start-up and heat transfer, and can optimize the thermal performance of TiO2-CLPHP. Meanwhile, TiO2-CLPHP TMS can ensure that the battery module has superior thermal performance. the battery module can be charged within the allowed temperature range (greater than 0 degrees C). under different low temperature environments (-5 degrees C, -15 degrees C, and -25 degrees C), the temperature of the battery module is basically maintained at 3.30 degrees C, 8.00 degrees C and 16.00 degrees C. The temperature difference between different areas of the battery module is within the allowable temperature difference range of 5 degrees C, which reduces the adverse effects of the battery aging caused by low-temperature charging and uneven temperature. Moreover, the battery module also has good electrical performance, the battery module voltage is in a low-level range in the early and middle stages of charging. During the complete charging process, the low-temperature charging capacity of the battery module has almost no attenuation, and the charging capacity ratio is as high as 95.92 %. Compared with the pure battery module, the charging capacity and charging efficiency of the battery module with the TiO2-CLPHP TMS has been improved to different degrees. Especially at -25 degrees C, the maximum charging capacity and charging efficiency can be increased to 24.51 %, and the minimum can be increased to 13.17 %. which ensures the efficient charging of the battery module. This proves that the designed TiO2-CLPHP TMS is feasible and effective for battery module heating management.