Sizes a battery energy storage system (BESS) from a backup power/duration requirement: usable energy, nameplate capacity (after DoD and round-trip-efficiency derating), maximum continuous power at the chosen C-rate, PCS DC voltage-window and AC power checks, and the AC interconnection cable.
Standards followed
IEEE 1547 (interconnection)IEC 62933 (electrical energy storage systems)IEC 61427-2 (RTE measurement/reporting)IEC 60364-5-52 (AC cable sizing, reused)
What it can do
- Converts a power+duration backup requirement into usable and nameplate battery energy, accounting for DoD and round-trip efficiency.
- Checks the bank's C-rate can actually deliver the required power.
- Checks the battery's voltage window against the PCS's DC input range.
- Sizes the PCS-to-load/grid AC cable using the same ampacity/voltage-drop engine as the Cable Sizing calculator.
- Advanced: multi-bank site aggregation and an approximate DoD-vs-cycle-life estimate.
Example problem
Size a Li-ion BESS for a 100kW critical load with 2 hours of required backup, at 90% DoD and 92% round-trip efficiency, discharging at 0.5C.
- Usable energy = Load × Duration = 100kW × 2h = 200 kWh.
- Nameplate capacity = Usable Energy / (DoD × RTE) = 200 / (0.9 × 0.92) ≈ 241.546 kWh.
- Max power at 0.5C = 0.5 × 241.546 ≈ 120.773 kW, which exceeds the 100kW requirement — C-rate check passes.
- AC cable sized to the PCS's rated output — the default scenario resolves to 70mm² at 0.52% voltage drop.
241.546 kWh nameplate capacity, 120.773 kW max power, 70mm² AC cable. With 2 identical banks, site energy aggregates to 483.092 kWh and the DoD-vs-cycle-life curve estimates ≈3750 cycles at 90% DoD (both advanced features).
Want the full step-by-step version?
Multi-bank site aggregation and the cycle-life estimate are advanced features \u2014 inputs remain editable but results show as locked on the core.