Parameters identification for open circuit voltage characteristic in battery models

A technique for the simultaneous online estimation of the battery state of charge (SOC) and the parameters of a polynomial approximation of the open circuit voltage dependence on SOC is proposed. The strategy is based on an equivalent circuit model of the battery and it consists of a Luenberger SOC observer interlaced with a recursive least-square algorithm for the parameters estimation. The well-posedness of the co-estimation problem for different structures of the open circuit voltage characteristic is discussed. The technique is validated on real data coming from an automotive application.