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Thermal Analysis of Parallel Connected Li-Ion Batteries For Hybrid Aircraft
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
Improving the energy performance of batteries will certainly increase the reliability of electric aircraft and thus their penetration into the market. To achieve this goal, battery management systems are required to keep the temperature below the safety limits and make the temperature distribution as even as possible within the battery pack and cells. Li-ion batteries are suitable for electric aircraft due to their high specific energy and advantage of energy density. In this study, 20 14.6 Ah prismatic batteries were connected in 2 parallel 10 series. Three-dimensional thermal analysis was performed for forced and natural transport conditions under 4 different discharge rates (0.5C, 1C, 2C, 2.5C) of the batteries. The study was conducted with Ansys Fluent. The NTGK Empirical model was chosen and a simple algorithm was used. A second order upwind method was chosen for pressure, momentum and energy equations. Batteries were tested for mesh independency. When the number of nodes in natural transport was increased from 43,204 to 345,560, the change in heat transfer was 0.1%. As the current rate given to the batteries increased, the batteries charged faster and their temperature increased. The ideal battery temperature appeared to be less than 313K. Consequently, for C ratios 2 and 2.5, forced convection should be applied where natural convection is insufficient.