State-of-charge (SOC) estimation based on reduced order of electrochemical model for a pouch type high power Li-polymer battery

Accurate estimation of SOC is the crucial factor to ensure safe operation of a battery. Current estimation methods are derived based on electric equivalent circuit models that do not take into account dependences of SOC on lithium concentrations, temperature, and other electrochemical phenomena. A new model for a Li-polymer battery was developed based on a 1D electrochemical microcell model. This model is capable of representing terminal behavior along with internal physical variables that include temperature, potentials, and ion flows. However, the model is very computationally intensive, necessitating order reduction for SOC estimation. A polynomial approach is applied to reduce calculation time of lithium concentration in the electrodes. Static and dynamic performance of this reduced model is compared with a full order model, including analysis of SOC and terminal voltage at different constant current rates. Step and pulses currents are also investigated.