Study on direct refrigerant cooling for lithium-ion batteries of electric vehicles

For the purpose of improving the working efficiency of lithium-ion batteries for electric vehicles (EVs), prevent battery catching fire and improve the economy of battery thermal management systems (BTMS), in this study a BTMS simulation model with direct cooling struct is built. The evaporator in the cooling circuit of the battery cells directly exchanges heat with the batteries. The performance of models using conventional R134a and environmentally friendly R1234yf was investigated without changing the model structure. The results show that: in normal temperature environment, the BTMS can effectively restrain the battery temperature from rising, the battery temperature would be suppressed under 305 K, the minimum difference of battery pack maximum temperature (T_max) and energy consumption of the BTMS using two refrigerants is 2 K and 2.3% respectively; when the working temperature is high, the BTMS can quickly drop the cells temperature below 313 K, and the shortest time difference that falling to 313K, is only 66s, and the minimum power consumption difference is 3.2%.