Design and Implementation of a Solar Panel-Based Battery Charging System with Protection and Voltage Limiting Circuits

This study aims to design and implement a simple solar panel-based battery charging system equipped with protection and voltage limiting circuits. The study was conducted to address the limitations of a direct solar panel-to-battery connection, which may cause short-circuit risk, reverse current, unstable charging voltage, and excessive battery charging. This research used a design-based experimental approach. The system was developed by preparing a block diagram, dividing it into several functional sub-blocks, and implementing the design into an electronic circuit. The main circuit sections consisted of solar panel protection, voltage limiter, interlocking circuit breaker, power regulator, and voltage divider. The assembled circuit was tested through real-time measurement by observing solar panel output voltage under different time and sky conditions and measuring battery charging time from different initial voltage levels. The results show that the solar panel output voltage varied according to time and weather condition. The lowest measured voltage was 15.0 V under cloudy conditions, while the highest measured voltage was 25.2 V under clear sky conditions around midday. The battery charging test showed that lower initial battery voltage required longer charging time, while voltage closer to the target level required shorter charging time. The evaluation was limited to voltage measurement and charging time; charging current, battery temperature, solar irradiance, and charging efficiency were not measured in detail. The proposed system can be applied for small-scale solar charging, educational practice, and basic renewable energy experiments. The study offers a practical circuit model that integrates protection, interlocking, voltage limiting, and regulation functions using simple and accessible electronic components.