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Battery Backup Time
Runtime from a battery bank on a given AC/DC load.
BatteryCore inputs only — quick sizing with engineering defaults.
Inputs (SI units)
Results
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Engineering Formula
- E_usable = V × Ah × DoD × η_inv / 1000 [kWh]
- t = E_usable × 1000 / P_load [h]
Backup time is stored energy divided by load, derated by DoD and inverter efficiency. Peukert's law reduces effective Ah at high C-rates for lead-acid.
Step-by-step Calculation
- 1.Usable energy
V×Ah×DoD×η/10007.07 kWh - 2.Runtime
E×1000/P7.07 h
Design Assumptions
- • Steady load (no motor inrush).
- • Battery at 25 °C, healthy (SoH > 90%).
Engineering Tips
- ◆Add 10–15% margin for real-world losses.
- ◆For inductive loads, size for 3× starting current.
Warnings
- ▲Never discharge lead-acid below 50% — halves cycle life.
Standards & References
IEC 61427IEEE 1013