<![CDATA[Changes in irradiation conditions cause photovoltaic (PV) power to be fluctuating, so the operating point of the PV is not always at the maximum power point. On the other hand, the battery charging process needs to be controlled so that it can be stopped when the battery reaches a full condition. This condition indicates the need for a control system that not only tracks the maximum PV power but also adjusts the charging process based on the battery's condition. This research develops a PV-based battery charging system using a buck converter that integrates Perturb and Observe (P&O) Maximum Power Point Tracking (MPPT), Proportional-Integral (PI) controller, and Coulomb Counting-based State of Charge (SOC) estimation. The P&O algorithm is used to determine the PV voltage reference, then the PI Controller adjusts the duty cycle of the buck converter so that the operating point follows this reference. Meanwhile, Coulomb Counting is used to monitor SOC and control the cut-off and restart charging mechanisms. The simulation results show that the system is capable of adjusting the PV operating point to changes in source conditions and maintaining the charging process under normal conditions. The battery SOC reaches 100% at around 3.45 s, followed by a decrease in duty cycle from about 0.5 to 0 and charging current to 0 A. These results show that the integration of MPPT, buck converter, and SOC-based supervision is capable of controlling the charging process according to PV operating conditions and the battery's SOC limits.]]>
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