Pulse-Current Charging Frequency Selection for a PV-powered EV-Lithium-ion Battery Pack

In recent times, the pulse-current (PC) charging has become more popular than constant-current-constant-voltage (CC-CV) charging for Lithium-ion (Li-ion) battery packs for electric vehicles (EVs). The PC frequency attains more investigation focus as it helps in battery life extension. The existing literature suggests that lower PC frequencies (< 1 Hz) and higher (> 1000 Hz) are beneficial. However, the Li-ion battery packs are charged by a DC-DC converter, and its dynamics have not yet been considered in PC frequency selection. This paper specifically addresses this issue. In experimental execution, a 250 W PV module charges two 48 V, 20 Ah Li-ion batteries via two Ćuk converters. Single battery charging and dual battery with simultaneous and consecutive charging modes are tested with PC frequencies 1, 2, 5, 10, 20, 50, 100, and 200 Hz. Through small signal analysis of the Ćuk converter, it is shown that the PC frequencies much less than critical frequency 72.46 Hz, are efficient and rapid for battery charging. Moreover, among all modes, the dual battery consecutive charging is recommended for PV to EV battery charging applications.