A multi-scale parameter adaptive method for state of charge and parameter estimation of lithium-ion batteries using dual Kalman filters

It is very important for the battery management system of electric vehicles to estimate the battery state of charge accurately and to achieve the on-line updating of the battery model parameters. In this paper, the estimation of the open circuit voltage is converted to the estimation of the open circuit voltage fitting parameters, the fast time-varying parameter open circuit voltage is converted into several slowly time-varying parameters. A multi-scale parameter adaptive method based on dual Kalman filters is developed. The multi-scale estimation of the battery state of charge and all parameters including open circuit voltage can be achieved. And the parameter adjustment method of dual extended Kalman filters in estimating multiple parameters is given. The experimental results show that the accuracy of the algorithm is improved by adding the estimation of the open circuit voltage. The proposed method can reduce the influence of the initial state error on the algorithm, and improve the robustness of the algorithm. •A multi-scale parameter adaptive method is developed for battery system.•The proposed approach estimate OCV by estimating OCV fitting parameters.•The proposed approach can estimate all battery parameters and SOC by different scales.•The method of adjusting parameters of dual extended Kalman filters is given.