An equivalent circuit model with variable effective capacity for LiFePO4 batteries

Abstract

A new approach to equivalent circuit models for LiFePO4 batteries is presented in this paper. The proposed battery model is a semi-physical nonlinear dynamic model with variable effective capacity. Fuzzy logic has been used to capture the nonlinear behavior of the battery in combination with continuous-time differential equations. Fuzzy logic blocks are embedded in a state-space dynamic model as nonlinear constructive blocks. The proposed model has been validated for three different LiFePO4 batteries. The model provides an intuitive physical analogy between charging LiFePO4 batteries and filling a semi-rigid tank, which is useful for explanatory purposes.