Simultaneous state and logarithmic parameter estimation of lithium-ion batteries using UKF

A rechargeable battery is one of the key technologies in hybrid electric vehicles (HEVs) and electric vehicles (EVs). Although it is important to know the states and parameters of the battery to maximize its efficiency and safety, there are still some difficulties in estimating them. This paper focuses on the simultaneous state and parameter estimation of the battery. The estimation often suffers from poor numerical stability, and to address this issue, simultaneous state and "logarithmic" parameter estimation of batteries is proposed and implemented. This approach is verified by performing a series of simulations under an EV operating environment.