A deterioration diagnosis method for Lithium-ion battery based on phase characteristics of internal impedance

A deterioration diagnosis method for a Lithium-ion battery based on a phase characteristic of its internal impedance is proposed in this paper. The phase characteristic of the internal impedance is obtained from transient voltage and current waveforms of the battery by DLT (Discrete Laplace Transform). The maximum phase is increased by the deterioration. Since the phase characteristic heavily depends on temperature, a correction method is proposed to diagnose the deterioration of the battery. The proposed battery diagnostic method is independent from a contact resistance having high dependence of the implementation of the battery. The deterioration rate can be estimated from the transient voltage waveform during the operation of the battery-driven equipment. Since non-linear calculation is excluded from the proposed method, the method realizes a diagnosis system at low cost.