Electric aircraft should be used more intensively due to the increase in energy consumption and the decrease in reserves of fossil fuels. Batteries are also an important factor in the development of electric aircraft. One of the most important parameters for the effective operation of batteries is the evaluation of heat dissipation. The even distribution or reduction of the heat generated during the operation of lithium-ion batteries extends the life of the batteries and ensures the safety of electric aircraft. In order to improve heat transfer dissipation in batteries in hybrid electric aircraft, it is necessary to increase the thermal conductivity of the coolant. For this reason, it has been suggested that solid particles with high thermal conductivity should be added to the coolant. In the present study, different battery thermal management strategies are suggested. To research the effect of nanofluids for thermal management in lithium-ion batteries, the study included two different base fluids (water and ethylene glycol) and three different volumetric fractions (1%, 2%, and 5%) of nanoparticle (Fe2O3) were added to these fluids. While the study was evaluated at four different discharge rates (1.0, 1.5, 2.0, and 2.5), the inlet velocities and temperature of the fluid were also changed. The cooling performances for 15 batteries module were examined and the simulation results showed that the nanofluid-based coolant could keep the temperature of the module at the desired value. As a result of the analysis, water was found to be the best nanofluid coolant parameter because it had a higher thermal conductivity than ethylene glycol. When the C value of the battery module was increased, that is, when the module was charged faster, its temperature increased. It was seen that the module was cooled better when the volume fraction of nanofluids and the speed of the refrigerant were increased.