Calculate off-grid solar battery bank capacity in Amp-Hours (Ah) and kWh. Supports 12V, 24V, and 48V LiFePO4 lithium and AGM lead-acid batteries.
ℹ️ Note: Wiring 2 units in series creates 24V strings; paralleling 6 strings provides 14.4 kWh (600 Ah @ 24V), safely satisfying the calculated 12.5 kWh minimum requirement.
The Solar Battery Calculator determines the exact battery storage capacity in Amp-Hours (Ah) and Kilowatt-Hours (kWh) needed to power your home during nights and extended cloudy periods.
Battery bank sizing centers around two primary engineering parameters: Days of Autonomy (how many days the system can run with zero solar generation) and Depth of Discharge (DOD). LiFePO4 Lithium Iron Phosphate allows 80% to 90% usable capacity and 4,000+ cycles, while Lead-Acid (AGM/Gel) must be limited to 50% DOD to avoid rapid cycle failure.
Our calculator also computes series and parallel battery wiring configurations to achieve your target 12V, 24V, or 48V DC bus voltage while maintaining balanced charging.
An off-grid retreat consumes 3,000 Wh daily on a 24V DC bus, requiring 2 days of autonomy using 12V 100Ah LiFePO4 batteries.
Gross Energy = (3,000 Wh × 2 Days) ÷ 0.80 DOD = 7,500 Watt-hours (7.5 kWh)
Two days of 3,000 Wh load with 80% maximum depth of discharge requires a gross storage capacity of 7,500 Wh.
Amp-Hours (Ah) = 7,500 Wh ÷ 24V = 312.5 Ah
Dividing total storage energy by system voltage yields 313 Ah of 24V battery capacity.
Single Battery = 12V × 100Ah = 1.2 kWh | Total Batteries = 7.5 kWh ÷ 1.2 kWh = 6.25 → 8 Batteries
To maintain balanced 24V series strings (pairs of two 12V batteries), round up to 8 batteries (4 strings of 2 batteries in series = 24V 400Ah = 9.6 kWh).
✅ Engineering Sizing Result: An 8-battery bank provides 9.6 kWh gross capacity (7.68 kWh usable), delivering 2.5 full days of complete off-grid autonomy.
Calculates the Amp-Hour capacity needed at the system DC bus voltage to protect against excessive discharge.
Determines how many batteries must be linked in series to build the system DC voltage bus.
| Daily Load (kWh) | 12V LiFePO4 (Ah) | 24V LiFePO4 (Ah) | 48V LiFePO4 (Ah) | Autonomy Reserve |
|---|---|---|---|---|
| 1 kWh / day (Shed/Van) | 208 Ah | 104 Ah | 52 Ah | 2 Days (2.5 kWh Bank) |
| 5 kWh / day (Cabin) | 1,042 Ah (Heavy Cable) | 521 Ah | 260 Ah (Best) | 2 Days (12.5 kWh Bank) |
| 10 kWh / day (Full Home) | Not Recommended | 1,042 Ah | 521 Ah (Best) | 2 Days (25.0 kWh Bank) |
| 20 kWh / day (Homestead) | Not Recommended | Not Recommended | 1,042 Ah (10x 100Ah 48V) | 2 Days (50.0 kWh Bank) |
LiFePO4 lithium batteries deliver over 4,000 charge cycles (compared to 500 for AGM), tolerate 80%-90% depth of discharge without degrading, charge 3x faster, weigh 65% less, and maintain consistent output voltage throughout their discharge curve.
Never mix batteries of different capacities, brands, chemistries, or ages. The weaker battery will drag down the stronger battery, causing internal circulating currents, severe imbalance, and premature pack failure.
To double voltage, wire batteries in series (positive of battery 1 to negative of battery 2). To increase capacity, wire batteries in parallel (positive to positive, negative to negative). For 48V, connect four 12V batteries in series.
Ensure your solar array generates enough daily energy to recharge the battery bank.
Next StepCalculate peak continuous AC power your battery bank must supply.
Next StepCalculate thick copper battery cables to prevent excessive voltage drop.
