A New Estimation Scheme for State-of-Charge in Battery Management Systems

P.-S. Kim, C.-W. Ha, B.-O. Min, E.-H. Lee, E.-T. Kim, and O.-S. Kwon (Korea)


Battery management, State-of-Charge(SoC), FIR filtering, Kalman filtering.


This paper proposes a new scheme for the real-time estimation of state-of-charge (SoC) for lead-acid cells in hybrid electric vehicles. The well known finite impulse response (FIR) filter is adopted for the estimation filtering. The proposed scheme provides the filtered estimates for the output voltage as well as voltages across the bulk and surface capacitors. These filtered estimates have good inherent properties. It is shown that the filtered estimate for the output voltage is not affected by voltages across capacitors when their initial values are constant on the window. It is also shown that the filtered estimate for voltages across capacitors is separated from the output voltage term. From discussions about the choice of window length and normalized noise covariance, it is shown that it can make the estimation performance of the proposed FIR filtering based scheme as good as possible. Via numerical simulations, the performance of the proposed scheme is shown to be superior to the existing Kalman filtering based scheme.

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