**Roxana-Elena Tudoroiu 1, Mohammed Zaheeruddin 2, Nicolae Tudoroiu 3,\* and Sorin-Mihai Radu 4**


Received: 4 August 2020; Accepted: 13 August 2020; Published: 14 August 2020

**Abstract:** The purpose of this paper is to analyze the accuracy of three state of charge (SOC) estimators of a rechargeable Li-ion SAFT battery based on two accurate Li-ion battery models, namely a linear RC equivalent electrical circuit (ECM) and a nonlinear Simscape generic model, developed in Part 1. The battery SOC of both Li-ion battery models is estimated using a linearized adaptive extended Kalman filter (AEKF), a nonlinear adaptive unscented Kalman filter (AUKF) and a nonlinear and non-Gaussian particle filter estimator (PFE). The result of MATLAB simulations shows the efficiency of all three SOC estimators, especially AEKF, followed in order of decreasing performance by AUKF and PFE. Besides, this result reveals a slight superiority of the SOC estimation accuracy when using the Simscape model for SOC estimator design. Overall, the performance of all three SOC estimators in terms of accuracy, convergence of response speed and robustness is excellent and is comparable to state of the art SOC estimation methods.

**Keywords:** SAFT lithium-ion battery; Simscape model; 3RC ECM Li-ion battery model; state of charge; adaptive EKF SOC estimator; adaptive UKF SOC estimator; particle filter SOC estimator
