Design and Experimental Validation of a Bidirectional DC–DC Converter for Charging a Lead-Acid Battery from a PV Panel

Abstract

Reliable battery charging remains a major challenge in standalone photovoltaic (PV) systems operating under continuously varying environmental conditions. This paper presents the experimental validation of an experimentally optimized priority-based finite-state machine (EO-PFSM) controller for a non-isolated bidirectional buck–boost DC–DC converter used to charge a 48 V lead-acid battery from a 340 W PV module. Unlike conventional charging techniques that continuously adjust the duty cycle through optimization-based algorithms, the proposed controller employs predefined PWM commands associated with discrete charging states, thereby reducing computational complexity while maintaining reliable charging performance. The controller was implemented using an Arduino Mega 2560 and experimentally evaluated under real outdoor operating conditions. A total of 1,039 operating samples were recorded during approximately two hours of testing. After excluding the startup transient interval, 1,012 valid steady-state samples were used for electrical and statistical analyses. The experimental results demonstrated stable transitions between the BOOST, BULK, and FLOAT charging stages while achieving an average converter efficiency of 94.06%. Furthermore, an independent logic-based load management strategy was successfully integrated without affecting the charging process. The obtained results demonstrate that the proposed EO-PFSM controller provides an effective balance between implementation simplicity, computational efficiency, charging reliability, and practical applicability for standalone photovoltaic battery charging systems.