Enhanced Lithium-ion battery model considering critical surface charge behavior.

• Solid-phase diffusion equation based surface SOC is proposed. • New enhanced ECM to describe low SOC behavior more precisely was proposed. • Battery test platform was built to conduct battery tests for model validation. • Proposed model's voltage RMSE at low SOC has been reduced to 8 mV. Battery model is the basis of battery efficient and safe management. The widely used equivalent circuit model (ECM) generally shows poor behavior in predicting battery terminal voltage at low sate of charge (SOC), increasing the risk in the urgent use of a battery at low voltage greatly. To model strong nonlinearity of battery open circuit voltage (OCV), a solid-phase diffusion equation based surface SOC is proposed to characterize OCV behavior and establish the new structure of the enhanced ECM to describe low SOC behavior more precisely. Finally, a battery test platform was built to conduct battery tests for model validation. The results show that the root mean square error (RMSE) of the battery terminal voltage obtained from the proposed model at low SOC has been reduced to 8 mV compared with the RMSE of 17 mV from the traditional ECM model. It is expected that the proposed model can be employed in battery management systems to effectively improve the reliability and safety of emergency use of a battery at low SOC. [ABSTRACT FROM AUTHOR]