Battery Capacity Calculator
Calculate the required battery capacity in amp-hours to power a load for a specified duration.
Total Battery Capacity
57.9 Ah
Total Battery Capacity vs Load Power
Formule
## Battery Capacity Sizing Battery capacity must account for the load, duration, efficiency losses, and depth-of-discharge limits. ### Formula **Required Ah = (P / V) x Hours / Efficiency / DoD** where P is load power in watts, V is battery voltage, Hours is the backup duration, Efficiency accounts for inverter and wiring losses, and DoD is the maximum allowable depth of discharge (to protect battery life).
Exemple Résolu
500 W load on a 48V battery system for 4 hours, 80% DoD, 90% efficiency.
- 01Load current = 500 / 48 = 10.42 A
- 02Usable capacity = 10.42 x 4 / 0.90 = 46.3 Ah
- 03Total capacity = 46.3 / 0.80 = 57.9 Ah
- 04Battery energy = 57.9 x 48 / 1000 = 2.78 kWh
Questions Fréquentes
What depth of discharge should I use?
Lead-acid batteries: 50% DoD for long life. Lithium-ion (LFP): 80-90% DoD. Lithium NMC: 80% DoD. Deeper discharge shortens battery cycle life. Manufacturer datasheets show cycle count vs DoD curves.
How does temperature affect battery capacity?
Battery capacity decreases in cold temperatures. Lead-acid loses about 1% capacity per degree C below 25 deg C. Lithium-ion is less affected but still loses 10-20% at 0 deg C. Apply a temperature derating factor.
What battery voltage should I choose?
12V for small systems under 1 kW. 24V or 48V for 1-5 kW. 48V for 5-10 kW. Higher voltage means lower current for the same power, allowing smaller cables and lower losses.
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