Battery Capacity Calculator
Estimate the battery capacity you need for your application. All calculations run in your browser — no data is uploaded or stored.
Inverter and wiring losses. 85–95% is typical.
LiFePO4: 80–90% typical. Lead-acid: ~50%.
How it works
Step 1 — Load energy: Power (W) × Hours = energy your load consumes (Wh).
Step 2 — Nominal battery energy: Load energy ÷ Efficiency ÷ Depth of discharge = the battery’s rated energy (Wh).
Step 3 — Battery capacity: Nominal energy (Wh) ÷ System voltage (V) = required Ah.
Important notes
- This is a planning estimate only — not a final engineering design.
- Peak/surge power: motors and compressors draw 3–7× their rated power at startup. Size your inverter and BMS for peak current, not just average load.
- Temperature: battery capacity drops in cold conditions (below 0°C). LiFePO4 should not be charged below freezing without heating.
- BMS limits: check the battery’s maximum continuous discharge current — your peak load must stay within it.
- Backup days: for off-grid solar, multiply by the number of cloudy days you want to ride through, and account for solar input.
- Always verify against the product datasheet and consult a qualified professional for system design.
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