Experimental Study on Thermal Management of 5S7P Battery Module with Immersion Cooling Under High Charging/Discharging C-Rates

In this study, the efficiency of an immersion cooling system for controlling the temperature of 5S7P battery modules at high charge and discharge C-rates was experimentally evaluated. The study was conducted in three main stages including the evaluation of different coolant oils followed by the proposition of an optimal volume flow rate (VFR) and cooling performance evaluation under high charging/discharging C-rates. In the first stage, three coolant oils, including Therminol D-12, Pitherm 150B, and BOT 2100, were compared. The Therminol D-12 achieved superior cooling performance, with the highest heat transfer coefficient (HTC) of 2171.93 W/m2⋅K and the ability to maintain the maximum temperature (Tmax) and temperature difference (∆T) of the battery module within the safe range. In the next stage, VFR was varied between 0.4 LPM and 1.0 LPM for the selected best coolant oil of Therminol D-12. The 0.8 LPM VFR was determined to be optimal with the highest HTC of 2445.73 W/m2⋅K and an acceptable pressure drop of 12,650 Pa, ensuring a balance between cooling performance and energy consumption. Finally, the cooling performance was evaluated at high charging/discharging C-rates from 1.5C to 3.0C for the proposed best coolant oil and VFR. The immersion cooling system with Therminol D-12 and a VFR of 0.8 LPM is an effective combination to achieve the desired performance of the battery module under extreme C-rate working conditions. The immersion cooling system with the proposed effective combination maintains the Tmax and ∆T at 38.6 °C and 4.3 °C under a charging rate of 3.0C and to 43.0 °C and 5.5 °C under a discharging rate of 3.0C.