UPS Battery Sizing Calculator — Formula
## UPS Battery Sizing
Proper battery sizing ensures the UPS provides the required runtime at the expected load.
### Formula
**Capacity (Ah) = (Load / Efficiency) x Runtime (hours) / Battery Voltage / DOD**
Where DOD is the maximum depth of discharge (80% for lead-acid to extend life, 90% for lithium).
### Sizing Considerations
- Battery capacity degrades over time (plan for end-of-life capacity)
- Temperature affects capacity (reduce by 1% per degree C below 25 C)
- Higher discharge rates reduce effective capacity (Peukert effect for lead-acid)
Proper battery sizing ensures the UPS provides the required runtime at the expected load.
### Formula
**Capacity (Ah) = (Load / Efficiency) x Runtime (hours) / Battery Voltage / DOD**
Where DOD is the maximum depth of discharge (80% for lead-acid to extend life, 90% for lithium).
### Sizing Considerations
- Battery capacity degrades over time (plan for end-of-life capacity)
- Temperature affects capacity (reduce by 1% per degree C below 25 C)
- Higher discharge rates reduce effective capacity (Peukert effect for lead-acid)
Exemplo Resolvido
2000 W load, 30 min runtime, 48 V battery, 90% inverter efficiency, 80% DOD.
- Runtime in hours: 30 / 60 = 0.5 hours
- Actual draw: 2000 / 0.90 = 2222 W
- Capacity: 2222 x 0.5 / 48 / 0.80 = 28.9 Ah
- Energy: 2222 x 0.5 / 0.80 / 1000 = 1.39 kWh
- Discharge current: 2222 / 48 = 46.3 A