State of charge estimation of a lithium ion cell based on a temperature dependent and electrolyte enhanced single particle model

SOC (state of charge) estimation provides critical information to system engineers and end users of consumer electronics to electric vehicles. The accuracy of model-based SOC estimation depends on the accuracy of the underlying model, including temperature effects that greatly influence cell dynamics. This paper uses a 7th order, linear, ESPM (electrolyte enhanced single particle model) as the basis for a Luenberger SOC observer for a lithium ion cell. Isothermal and non-isothermal simulations compare the SOC from a commercially-available finite volume code and the SOC estimate for a wide range of temperature (0 ≤ T ≤50 °C) and pulse C-rates (|I|≤15C). Arrhenius relationships between the ESPM model parameters and the sensed temperature improve SOC estimation. At low temperature (T< 10 °C) and low C-rates, temperature measurement reduces the RMS (root-mean square) SOC estimation error by up to ten times. At high temperature T≥ 40 °C and high C-rates (|I|≤15C), temperature measurement decreases SOC estimation error by more than three times.