Thermal and electrical analysis of 26650 li-ion batteries in series connection using the NTGK model and virtual simulations

Lithium-ion batteries are extensively used in various renewable sources such as renewable energy storage systems, electric vehicles, and portable electric vehicles due to their storage properties. However, since they are significantly affected by ambient temperature, their lifetime and safety issues in general negatively affect their electrical performance. In order to ensure that batteries achieve their optimum potential, it is necessary to understand the interaction between charge and discharge rates and temperature changes very well. In this study, the electrical characteristics of 26650 lithium-ion batteries were analyzed in series under different environmental conditions and different discharge rates. To understand the relationship between environmental temperatures and battery performance, Newman, Tiedemann, Gu, and Kim (NTGK) evaluated the effectiveness of previously used models in predicting these effects. The Ansys Battery Ntgk model was used to predict the temperature behavior and voltage variations under different outdoor temperature conditions. In this study, four ambient temperatures (273 K, 283 K, 298 K, and 318 K) and four discharge rates (0.5C, 1C, 1.5C, and 2C) were investigated to study the thermal characteristics and voltage variations. The mesh independence study was carried out in detail at the beginning of the analysis to validate the simulation results. The results show that the discharge time is significantly reduced due to increased internal resistance and electrochemical side reactions. The 1S1P battery design exhibits a maximum internal temperature of 303.2 K at an ambient temperature of 273.15 K and 336.7 K at an ambient temperature of 318.15 K, while the 2S1P battery design exhibits an even higher maximum temperature of 341.3 K at an ambient temperature of 318.15 K, indicating that compound heat buildup occurs in series connections.