Modeling and validation of a three-dimensional thermoelectric model of a 50 Ah lithium-iron-phosphate battery cell at three different ambient temperatures in the New European Driving Cycle (NEDC)

Abstract:
In this work a three-dimensional thermoelectric model of a 50 Ah lithium-iron-phosphate battery cell (LFP cell) is created in SimulationX. The Rint-model is used in order to describe the electrical behavior of the LFP cell. The electrical parameters such as capacitance C, the open circuit voltage Uoc, the charging resistor Rch, and the discharge resistor Rdisch are identified measurements from a battery test bench at different ambient temperatures (0 °C, 25 °C, 40 °C), currents (25 A, 50 A, 100 A) and at different state of charge (1/ 0.8 / 0.6 / 0.4 / 0.1 / 0). The thermal modeling of the LFP cell takes into account the heat absorption and release by the heat conduction, convection, thermal radiation and an internal heat source. The thermal parameters such as the specific thermal conductivity λ, the specific heat capacity cp, and the emission coefficient ? is determined by theoretical methods known in the literature. To generate the electric power of the battery a low engine power electric car with a 75 kW electric motor and a total mass of 903 kg is created in Advisor (Matlab/Simulink) and the NEDC is simulated. The characteristics of the power is exported to SimulationX and equally divided on a battery with 96 LFP cells. After that the three-dimensional thermoelectric model of a LFP cell (in a battery test system) is validated in a laboratory at temperatures of 11.35 °C, 26 °C and 32.85 °C and a depth of discharge of 0.