Live Demo — Battery Capacity Calculator
Enter your daily load, consecutive rainy days and battery type to get the required battery capacity in amp-hours instantly.
Battery Capacity Calculator
Free professional battery sizing calculator for solar lighting systems. Input your daily power consumption, night consumption, consecutive rainy days and minimum ambient temperature, choose a battery type, depth of discharge and system voltage to determine the required energy, apply a temperature correction factor, and get a recommended battery capacity in Ah.
Key Features
Load Parameters
Enter daily power consumption and night-only consumption in Wh to define the energy your battery must supply over 24 hours.
Environment Parameters
Set the number of consecutive rainy days the battery must cover alone and the minimum ambient temperature in °F.
Battery Type & DoD
Choose lead-acid, gel or lithium chemistry with an appropriate depth of discharge (lead-acid 50-70%, lithium 80-90%).
System Voltage
Select the system operating voltage (12V / 24V / 48V) to convert the required energy into battery amp-hour capacity.
Temperature Correction
An automatic correction factor compensates for the capacity loss of batteries operating at low ambient temperatures.
Recommended Battery
Get a commercial battery rating in Ah that covers your rainy-day autonomy requirement with a clear result breakdown.
Technical Specifications
| Platform | HTML5 Web App | Android (via WebView) |
| Core Calculation | C_battery = E_total / (V_system × DOD × η_battery), then × K_temp |
| System Voltage | 12V / 24V / 48V |
| Daily Power Consumption | 10 - 5000 Wh/day |
| Consecutive Rainy Days | 1 - 10 days |
| Minimum Temperature | -4 to 104 °F (correction factors up to 1.3) |
| Battery Type | Lead-acid / Gel / Lithium |
| Depth of Discharge | 30% - 90% (lead-acid 50-70%, lithium 80-90%) |
| Battery Efficiency | 85% - 98% |
| Industry Standards | IEC 61427-1, IEC 62620, IEEE 485, AS/NZS 4509.2 |
| Output | Total required energy + base & corrected capacity + recommended battery (Ah) |
Frequently Asked Questions
How is the required battery capacity calculated?
The calculator first multiplies daily power consumption by the number of consecutive rainy days (E_total = P_daily × N_days), then divides by the product of system voltage, depth of discharge and battery efficiency (C_battery = E_total / (V × DOD × η_battery)). The result is then multiplied by a temperature correction factor to obtain the final capacity in Ah.
What is the temperature correction factor for?
Battery capacity falls as temperature drops because chemical reactions slow down. The tool applies a factor of 1.3 below 14°F (-10°C), 1.1 below 32°F (0°C), 1.05 below 50°F (10°C), 1.0 below 68°F (20°C) and 0.95 below 86°F (30°C), so cold-climate installations get a bigger battery.
Why do lead-acid and lithium batteries need different DoD values?
Depth of discharge limits how much stored energy can be safely used. Lead-acid chemistry is damaged by deep discharge, so a DoD of 50-70% is typical, while lithium batteries tolerate 80-90%. Using the correct DoD protects the battery and extends its cycle life in the solar lighting system.
What does the recommended battery result mean?
The recommended battery value rounds the corrected capacity up to a practical commercial rating in Ah (for example 200Ah or 220Ah). It is the battery size that keeps the lighting system powered through the specified consecutive rainy days without any solar charging.
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