Disclaimer: RacewayIQ is an informational engineering tool only. All calculations must be independently verified by the user. Do not rely on these results as the sole basis for design, procurement, installation, construction, permitting, or code compliance decisions.

UPS Battery Runtime Calculator

Estimate UPS battery runtime from connected load, battery arrangement, efficiency, depth of discharge, and aging assumptions.

This calculator provides a simplified energy-based UPS runtime estimate. Final UPS and battery selection should be verified using manufacturer runtime charts, discharge curves, battery chemistry data, cutoff voltage, temperature, age, and actual UPS load characteristics.

Job Information

Project nameLocationPrepared byDateNotes

Main Inputs

UPS calculation modeEstimate runtime, check a required runtime, or estimate required battery capacity from the same energy assumptions.Load entry modeUse simple total load until a detailed load list is reviewed separately.Supported load (W)Enter the load supported by the UPS after realistic equipment load, diversity, and redundancy assumptions.Required backup runtime (minutes)Enter the required backup time from owner criteria, code, project specification, or system design.Battery block/module voltage (V)Use the voltage of one battery block or module.Battery capacity per block/module (Ah)Use the rated amp-hour capacity for one battery at the relevant discharge rate when available.Battery blocks/modules in seriesEnter how many battery blocks/modules are connected in series to build the DC string voltage.Parallel battery stringsEnter how many identical series strings are connected in parallel.

Advanced Inputs

Use these when the job has project-specific assumptions, manufacturer data, or review conditions.

UPS / inverter efficiency (%)Use manufacturer efficiency when available. Lower efficiency reduces usable runtime.Usable depth of discharge limit (%)Limit this to the usable portion allowed by the battery type, UPS design, and manufacturer recommendations.Battery aging / end-of-life factorUse a value below 1.0 to reserve capacity for battery aging and end-of-life performance.UPS name / equipment tagUPS typeBattery chemistryLoad typeEnvironmentManufacturer data source / notesManufacturer runtime data verified

Result

Review

Supported load

1000 W

Required backup runtime

300.0 min

Estimated runtime

331.8 min

Runtime margin

31.8 min

DC string voltage

48.0 V

Total battery bank capacity

200.0 Ah

Nominal battery energy

9600 Wh

Usable battery energy

5530 Wh

Runtime utilization

90.4%

Required usable energy

5000 Wh

Required Ah at DC bus

180.8 Ah

Status

Review Required

Reason

Estimated runtime exceeds required runtime, but utilization is above the review threshold and manufacturer discharge curves must be verified.

Practical Next Steps

Treat this as a workable planning result that still needs review.
Resolve warnings that are close to limits, based on manual assumptions, or missing manufacturer data.
Confirm the result against the project specification before procurement, permitting, or installation.

This energy-based estimate does not replace manufacturer UPS runtime charts or battery discharge curves.

Runtime utilization is above the review threshold. Verify manufacturer runtime data, battery aging, temperature, cutoff voltage, and load assumptions.

Lead-acid runtime may be affected by discharge rate, Peukert effects, temperature, aging, and cutoff voltage.

Manufacturer runtime or discharge data was not entered. Treat the result as a planning estimate.

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Calculation Breakdown

Battery Bank

UPS calculation mode: Check Required Runtime
UPS name / equipment tag: Not entered
UPS type: Online Double Conversion
Battery chemistry: VRLA Sealed Lead Acid
Load type: Mixed Loads
Environment: Indoor Conditioned
Battery block/module voltage: 12 V
Capacity per block/module: 100 Ah
Series blocks/modules: 4
Parallel strings: 2
DC string voltage: 12 V x 4 = 48 V
Total battery capacity: 100 Ah x 2 = 200 Ah

Nominal Energy

Nominal energy: 48 V x 200 Ah = 9,600 Wh

Usable Energy

UPS / inverter efficiency: 90%
Usable depth of discharge limit: 80%
Battery aging / end-of-life factor: 0.80
Usable energy: 9,600 Wh x 0.90 x 0.80 x 0.80 = 5,530 Wh

Runtime

Supported load: 1,000 W
Estimated runtime: 5,530 Wh / 1,000 W x 60 = 331.8 min

Required Runtime Check

Required backup runtime: 300 min
Runtime margin: 331.8 min - 300 min = 31.8 min
Runtime utilization: 300 min / 331.8 min = 90.4%
Status: Review Required
Reason: Estimated runtime exceeds required runtime, but utilization is above the review threshold and manufacturer discharge curves must be verified.

Required Battery Capacity

Required usable energy: 5,000 Wh
Required nominal battery energy: 8,681 Wh
Required Ah at DC bus: 180.8 Ah

Code and Design References

Manufacturer Runtime Data

Final UPS runtime should be verified using manufacturer runtime charts, battery discharge curves, and UPS model-specific data.

Use the manufacturer's runtime or constant-power discharge data for final selection.

Battery Chemistry

Battery performance depends on chemistry, discharge rate, cutoff voltage, temperature, age, and manufacturer limits.

Efficiency and Internal Consumption

UPS efficiency, charger behavior, internal consumption, and inverter losses affect usable runtime.

End-of-Life Capacity

Battery aging and end-of-life criteria may require additional capacity margin.

Temperature

Ambient temperature can significantly affect battery capacity and life.

Load Assumptions

Actual runtime depends on connected load, load profile, redundancy assumptions, and equipment behavior during outage.