Live Demo — Solar Charging Time Calculator
Enter panel power, peak sun hours and battery state of charge to see how long the battery takes to reach full charge.
Solar Charging Time Calculator
Free professional solar charging time calculator for solar lighting systems. Input solar panel power, PV system efficiency, local peak sun hours, battery capacity, system voltage, charging efficiency and initial/target state of charge to determine the equivalent full-power charging time and how many sunny or cloudy days the battery needs to reach full charge.
Key Features
Solar Panel Parameters
Enter panel power in Wp, overall PV efficiency and local peak sun hours to model daily energy production.
PV Efficiency Model
Account for module degradation, tilt, soiling and wiring losses with a single efficiency factor, typically 70-85%.
Battery & Charging Target
Set battery capacity, system voltage, charging efficiency and the start and target state of charge (SOC).
Charging Time Result
Get the equivalent full-irradiance charging time in hours and the actual number of sunny days required.
Cloudy-Day Estimate
With reduced effective charging hours, see how many days a cloudy period would need to top up the battery.
PSH Region Reference
Built-in table gives annual average and winter minimum peak sun hours for different regional climates.
Technical Specifications
| Platform | HTML5 Web App | Android (via WebView) |
| Core Calculation | E_needed = C × V × ΔSOC / η_charge; T_charge = E_needed / (P_pv × η_pv) |
| Solar Panel Power | 1 - 5000 Wp |
| PV System Efficiency | 30% - 100% |
| Peak Sun Hours | 0.1 - 24 h/day |
| Battery Capacity | 1 - 1000 Ah |
| System Voltage | 12V / 24V / 48V |
| Charging Efficiency | 50% - 100% (MPPT ~95%, PWM ~85%) |
| Initial / Target SOC | 0% - 100% |
| Industry Standards | IEC 62509, IEEE 1562 |
| Output | Charging time (h) + recharge days under sunny and cloudy conditions |
Frequently Asked Questions
How is the solar charging time calculated?
First the energy needed is E_needed = C × V × ΔSOC / η_charge, where ΔSOC is the difference between target and initial state of charge. Dividing by the panel output gives the charging time T_charge = E_needed / (P_pv × η_pv). For a 12V 200Ah battery charging from 50% to 100% with a 300Wp panel, that is about 4.95 equivalent hours.
What is peak sun hours (PSH)?
PSH equals the daily total irradiation in kWh/m² divided by 1000 W/m², so it is the number of hours of full 1000 W/m² sun equivalent. It is the standard way to compare solar resources, and it directly drives daily generation E_pv = P_pv × PSH × η_pv.
Why does charging efficiency differ between MPPT and PWM?
MPPT controllers track the panel maximum power point and convert it efficiently to battery voltage, reaching about 95% charging efficiency, while PWM controllers simply clamp voltage and reach about 85%. Choosing MPPT can cut the recharge time significantly, especially in low-light weather.
What does the charging days result mean?
It converts the equivalent full-irradiance charging time into real calendar days by dividing by local PSH. With PSH = 5h, a 4.95h charge is reached in about 1 sunny day; with only 3h of effective charging on cloudy days it would take about 1.65 days. As a design rule, size the panel so daily yield is 1.2-1.5 times the daily load.
Thank you for choosing Open Solar Design