A novel battery module series-parallel switching strategy applied to automated guided vehicle charger

Abstract

This research aims to develop an automated guided vehicle (AGV) charger featuring a switch array circuit. This circuit integrates series charging, single-module charging, parallel voltage balancing, and parallel discharge capabilities of battery modules to optimize charging and discharging processes for AGVs. This study proposes a low-cost architecture utilizing only six MOSFETs and incorporating a Miller plateau to achieve active energy balancing between two battery modules. The proposed control strategy not only effectively balances the energy discrepancies between two modules but also significantly enhances the overall endurance performance of the AGV system. It facilitates the switching between series and parallel configurations of the battery modules. Series charging mitigates uneven current flow and improves charger efficiency in high-voltage and low-current states. Single-module charging enables independent charging with voltage limit control for batteries with low energy. To address variations in battery characteristics, this study leverages power switches in the ohmic region and employs the Miller effect for preliminary balancing of the battery modules. The Miller effect is used not only for cost-effective balancing of battery modules but also to prevent the high current that results from voltage imbalances when connecting battery modules in parallel. The parallel discharge mode, activated through a switch array, aims to extend the battery life of the AGV. A hardware prototype of the proposed system has been developed, and experimental findings have been gathered to validate its feasibility and effectiveness under various load conditions.