Lithium-ion batteries SoC estimation using a robust non-linear Lipschitz observer

One of the most important challenges in estimating lithium-ion battery parameters, including estimating the charge level, is model uncertainties. In other words, the uncertainties of the model cause the performance of the estimator to decrease drastically and the estimation error to increase. To solve this problem, this paper presents a robust method for estimating lithium-ion battery parameters, namely a non-linear Lipschitz estimator. In this estimator, model uncertainties are considered in the main battery model and in the battery output equations. Considering these uncertainties in the battery modeling and design of the desired estimator, the variables of the battery state space model, including the charge level and the battery terminal voltage, are estimated with high accuracy and in a way that is resistant to uncertainties. The estimator's stability is proved through the Lyapunov theory, and its performance for SoC estimation is investigated through a series of laboratory tests. The results of the experiments show the effectiveness of the suggested approach for robust estimation of the battery SoC in the presence of model uncertainties. The results of the tests showed that the proposed method is more accurate than the ampere-hour method for estimating the SoC and terminal voltage as much as 1% and 2 V, respectively.