To effectively charge photovoltaic solar panels, one must focus on 1. Utilizing direct sunlight, 2. Direct sunlight exposure is critical, as photovoltaic panels convert. Estimate how long it takes your solar panel to charge a battery based on panel wattage, battery capacity, voltage, and charge efficiency. Formula: Charging Time (h) ≈ (Battery Ah × V × (Target SOC / 100)) ÷ (Panel W × (Eff% / 100)). Adjust for sunlight hours to find daily charging duration. But before you start charging your solar charger, it's. Basic Operation: Solar panels work by converting sunlight into direct current (DC) electricity through photovoltaic cells, which can then be stored in batteries for later use.