Abstract
Small Off-Grid photovoltaic systems require a charge controller to transfer energy safely from the photovoltaic module to the battery. This study characterizes the input-output performance of a 30 A pulse-width-modulation solar charge controller connected to a 20 Wp photovoltaic module and a 12 V, 12 Ah battery. Field measurements were conducted in Tunggul Wulung, Lowokwaru, on 5 September 2026 at one-hour intervals from 08:00 to 16:00. Solar irradiance, module surface temperature, photovoltaic voltage-current, and battery-side voltage-current were recorded. Input power, battery charging power, instantaneous measured efficiency, and interval energy efficiency were calculated. Irradiance ranged from 5.0 to 143.8 W/m² and module temperature from 25.4 to 62.5 °C. The maximum panel power was 2.680 W at 08:00, whereas the maximum battery-input power was 2.361 W at 10:00. Trapezoidal integration yielded 12.524 Wh of panel energy and 10.647 Wh of battery-input energy, corresponding to an aggregate energy efficiency of 85.01%. Instantaneous ratios above 100% at 14:00-16:00 occurred at very low power and are interpreted as apparent efficiencies affected by measurement resolution and non-simultaneous readings, not as physical conversion gains. The results provide a preliminary field baseline and emphasize synchronized measurements and uncertainty reporting for subsequent testing.