Electrical and Thermal Modeling of a Lithium Titanate Oxide based Battery for Railway Application

Summary:

The electrical and thermal behaviour of a prismatic LTO cell is analyzed and modelled for different operation ranges. Afterwards the validated models are used to simulate a complete traction battery compromising of over 1000 interconnected cells for a high-power railway application. Under consideration of side cooling pipes and cell-to cell variations the whole traction battery was simulated and validated using the open source available ISEA Framework.
The electrical behavior of the cell is analyzed, with the help of electrochemical impedance spectroscopy (EIS) measurements, that were performed under variation of temperature and SOC. Afterwards these measurements were used to fit the parameters of a 2RC electrical equivalent circuit (EEC). Besides the electrical model of a cell, the thermal model also plays a significant role. Due to the strong temperature dependency of battery systems, an exact representation of the thermal behavior can help to estimate the thermal stability of the whole system. Within a cell, the amount of heat radiation from the individual components is insignificantly low. Additionally, the influence of convection between the electrolyte and the electrode can be neglected due to the limited flow velocity of the electrolyte. Accordingly, the most dominant effect of heat transfer within a cell is heat conduction, which shows anisotropic behaviour and is calculated by considering individual material parameters.
The electrical and thermal model are both validated, using prior conducted measurements at cell level. Afterwards the combined electrical and thermal models are used to model and simulate a high-power traction battery for railway application.