Non-Invasive Experimental Identification of a Single Particle Model for LiFePO4 Cells

TL;DR

This paper presents a non-invasive method to identify a Single Particle Model for LiFePO4 batteries, improving accuracy in high-power applications and outperforming traditional models at higher discharge rates.

Contribution

The work introduces a novel two-step, non-invasive identification procedure tailored for LiFePO4 chemistry, enhancing model accuracy for battery management systems.

Findings

SPM maintains RMSE < 50 mV at 3C discharge

Model comparison shows SPM outperforms ECM at high currents

Identification process is non-invasive and voltage-current based

Abstract

The rapid spread of Lithium-ions batteries (LiBs) for electric vehicles calls for the development of accurate physical models for Battery Management Systems (BMSs). In this work, the electrochemical Single Particle Model (SPM) for a high-power LiFePO4 cell is experimentally identified through a set of non-invasive tests (based on voltage-current measurements only). The SPM is identified through a two-step procedure in which the equilibrium potentials and the kinetics parameters are characterized sequentially. The proposed identification procedure is specifically tuned for LiFePO4 chemistry, which is particularly challenging to model due to the non-linearity of its open circuit voltage (OCV) characteristic. The identified SPM is compared with a second-order Equivalent Circuit Model (ECM) with State of Charge dependency. Models performance is compared on dynamic current profiles. They exhibit similar performance when discharge currents peak up to 1C (RMSE between simulation and measures smaller than 20 mV) while, increasing the discharge peaks up to 3C, ECM's performance significantly deteriorates while SPM maintains acceptable RMSE (< 50 mV).