Equalization chargers using capacitor-diode networks for series-connected energy storage cells

Conventional cell equalizers based on dc-dc converters require many switches or transformers as the number of series connections increases, raising their cost and complexity and decreasing reliability. This paper proposes a novel equalization charger that consists only of a capacitor-diode network and an ac power source. A dual capacitor-diode network configuration is also proposed to mitigate the RMS current flowing through energy storage cells during charging. The operating principle and derivation of a dc equivalent circuit are explained. Experimental charge tests were performed on series-connected supercapacitors to demonstrate the charge performance and analyze the operating waveforms.