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Battery Backup Calculator — UPS / Inverter Runtime
Estimate UPS or inverter backup from battery-bank configuration, state of charge, capacity allowance and AC load.
ELECTRICAL TOPICBattery Backup Calculator
Your result
BACKUP ESTIMATEREADY
—Enter values below and press Calculate.
RESULT DISPLAYV × Ah → hours
Calculation details & exports
Inputs used
ElectricalTopic.com Tools© 2026 ElectricalTopic.comV × Ah → hoursFormula and worked example
Bank V = battery V × series count; bank Ah = battery Ah × parallel strings. Usable Wh = bank V × bank Ah × remaining-capacity fraction × (start SOC − minimum SOC) / 100. Hours = usable Wh / (AC watts / inverter efficiency + additional DC idle watts).
Worked example
Two 12 V batteries in series per string and two parallel strings, each battery 150 Ah, form a 24 V / 300 Ah bank. With 80% remaining-capacity allowance, SOC from 100% to 50%, 90% inverter efficiency, zero additional idle draw and 1,000 W AC load, estimated backup is 2.592 hours (155.52 minutes).
Using this tool
Enter the actual equipment and project values. The Use example button loads an illustrative case. Calculation happens in your browser; no Python, API key or account is required. Use the result details to see the inputs and scope, copy the result, download CSV or print.
Series में voltage बढ़ता है, Ah नहीं। Parallel strings से Ah बढ़ता है। यह energy estimate है; वास्तविक runtime के लिए battery/UPS discharge chart, cut-off और load conditions देखें।
Common questions
Is this guaranteed UPS runtime?
No. The energy model does not reproduce every battery discharge curve, temperature effect, Peukert effect, BMS/cut-off setting or inverter overload condition.
Can I add series battery Ah values?
A series string retains the Ah capacity of an individual equal battery while its voltage adds. Parallel equal strings add bank Ah.
Which load should I enter?
Enter the actual AC watts expected during backup, not UPS kVA or the sum of equipment labels without considering simultaneous use.
Related practical guides
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Formula references and model scope
Formula review: 2 November 2026. Examples are illustrative. Enter project-specific data; a planning result does not certify an installation or equipment selection.
