Inflection Point Engineering Calculators

UPS / DC Battery Sizing

Constant-power battery sizing per IEEE 485 (lead-acid) / IEEE 1115 (NiCd). Enter a stepped load profile; the tool computes total duty kWh, required cell kWh with design/aging/temperature correction, and approximate Ah capacity.

Standards: IEEE 485-2020 (Lead-Acid Sizing for Stationary Applications), IEEE 1115 (NiCd Sizing). Method: constant-power (kWh-per-cell) method; load profile is step-profiled and summed as kWh, then distributed per cell and multiplied by design (Kd), aging (Ka), and temperature (Kt) correction factors. Typical factors: Kd 1.10–1.25, Ka 1.25 (80%-EOL), Kt 1.11 at 60°F per IEEE 485 Tab 1. Ah estimate at Vcell_nom is preliminary — confirm against manufacturer capacity-vs-time curves.

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© 2026 Inflection Point Engineering, LLC. All rights reserved.