Zero-current-switching pulse charger for high capacity batteries in renewable energy applications

Abstract

Fast charging of high capacity batteries is of great concern, especially in renewable energy and electric vehicle (EV) applications. Pulse charging has become the preferred method for fast charging with heavy currents. However, it presents drawbacks due to switching losses involved in hard-switching of semiconductor devices. This paper presents a soft switched pulse charging mechanism for high capacity Pb-acid and Li-ion batteries, which minimises switching losses that makes the methodology very suitable for implementing the National Electric Code (NEC) level-1, level-2 chargers or specially the level-3 charger more conveniently for EVs. The fully clamped quasi-resonant DC link (FCQDL) converter generates current pulses to charge the battery in a zero-current switching (ZCS) manner to minimise switching losses. The simulated and experimental results show that the proposed charger can implement constant current (CC) and constant voltage (CV) modes of charging. The experimental results show that the proposed charging methodology reduces the charging time of Pb-acid batteries by 14.01 % in contrast to the conventional CC-CV charging method. Furthermore, discharging curves for the conventional and pulse charging methods are compared to evaluate the effective useful charge that is put into the battery. The results reveal that the effective charge capacity of a battery is significantly improved due to the use of pulse charging.