Comparing open-circuit voltage hysteresis models for lithium-iron-phosphate batteries

The hysteresis in the state-of-charge (SoC) vs. open-circuit voltage characteristic of a lithium-iron-phosphate (LiFePO₄, LFP) battery is modelled with two approaches. The first one is based on a first-order charge relaxation equation, the second one is the Preisach model implemented with the Everett function. The advantages and drawbacks of the methods are discussed. Simulation results are compared for a 20 A h LFP cell, stimulated with various SoC evolutions, allowing us to draw minor loops in the SoC-OCV plane. The results are also compared to experimental data.