Battery Charger with Impedance Spectroscopy Capability for Li-Ion Cells

Inhalt:
This paper presents the design and modeling of a charger for LiFePO4 lithium-ion cells based on a multiphase resonant converter. The combined phase-shift control together with frequency control of the resonant converter as well as its wide bandwidth enables the built-in implementation of the Electrochemical Impedance Spectroscopy (EIS) technique for carrying out the battery cell characterization. The resonant converter is designed as a voltage controlled current source. In this way, the maximum current is limited inherently, while the maximum voltage is set by a control loop. The EIS study is carried out in galvanostatic mode. The high-capacity ANR26650M1 LiFePO4 is chosen as experimental battery cell to validate the proposal.