Experimental investigation of the innovated indirect-cooling system for Li-ion battery packs under fast charging and discharging

Liquid-cooled systems could effectively manage the temperature of the LIB pack under discharge/charge con-ditions. The current experimental work proposes an innovative active cooling system for controlling the heat generated through the 21700-format lithium-ion batteries on the basis of AgO nanofluid and copper mold. The effects of charge/discharge C-rates, volume fractions of AgO nanoparticles, the velocity of inflow coolant, and temperature of inlet liquid on the thermal efficiency of the LIB pack are analyzed comprehensively. Adding silver-oxide nanoparticles with different volume fractions which included 1 %, 2 %, and 4 % to the deionized water, notably decreased the maximum temperature of the LIB pack by 7.3 %, 11.1 %, and 12.4 %, respectively, in comparison with the water-cooled system during the fast discharging operation. The cooling system with 4 %-VF AgO-nanofluid decreased the peak temperature and temperature dissimilarity of the batteries under 5C discharge operation by about 4.83 degrees C and 1.17 degrees C, respectively. Moreover, the temperature differences of the batteries with 0.28 m s-1 inflow velocity of the cooling channel during the charge and discharge processes declined by 26 %, and 21.5 %, respectively, compared to 0.16 m s-1 coolant velocity. As a result, an increase in the rate of inlet coolant leads to the decline of the peak temperature and temperature diversity. In addition, results showed that using higher inlet coolant temperatures significantly increased both the highest experienced temperature and temperature diversity within the batteries throughout the discharge operations by about 3.6 degrees C, and 1.6 degrees C, respectively, when the inlet fluids' temperatures increased from 20 degrees C to 35 degrees C. The experimental results indicate that these strategies can decline the peak temperature and temperature diversity of the batteries with inlet liquid temperature of 35 degrees C under 5C discharge operation to acceptable values such as 34.41 degrees C and 4.55 degrees C, respectively.