UPS energy-method runtime equations
Nominal battery energy is reduced by UPS efficiency, remaining capacity, and permitted depth of discharge.
Enom = Vbattery × Ns × Ah × NpEusable = Enom × η × Faging × DODt = Eusable/PloadIDC = Pload/(Vbank × η)where:
- Ns
- Series battery count
- Np
- Parallel string count
- η
- UPS efficiency
- t
- Energy-method runtime[h]
Use manufacturer constant-power discharge tables for final runtime.
How to use the UPS Backup Time Calculator
Estimate UPS battery runtime from load, battery voltage and Ah, series and parallel configuration, inverter efficiency, aging, and depth of discharge. Start by choosing the operating mode, then enter values from nameplates, measurements, or project documents in the units shown. The result updates immediately and keeps intermediate quantities visible for review.
- Confirm the system and calculation mode.
- Enter measured or manufacturer-rated values.
- Review the primary result and intermediate metrics.
- Continue with the related protection or equipment-selection checks.
Calculation method and validation
The equations and symbol definitions above show the complete calculation basis. Inputs are checked before calculation so zero, negative, incompatible, or physically impossible combinations are flagged instead of silently producing a misleading result.
How to interpret the result
Use the main result as a starting value and read every supporting metric. Battery Ah is valid at the required discharge rate Load and efficiency are constant Series batteries are identical and balanced A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.
- Battery Ah is valid at the required discharge rate
- Load and efficiency are constant
- Series batteries are identical and balanced
Selection limits and next checks
Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions. Energy-method runtime can overestimate high-rate lead-acid performance due to Peukert and cutoff effects. Use the UPS and battery manufacturer runtime or constant-power discharge table for final selection. Compare the output with the current applicable standard, local rules, exact VIOX product datasheet, environmental conditions, protection coordination, and the engineer's project requirements before procurement or installation.
Continue with battery capacity converterContinue with battery c rate runtime calculatorContinue with stationary battery sizing calculator
Assumptions
- Battery Ah is valid at the required discharge rate
- Load and efficiency are constant
- Series batteries are identical and balanced
Important Warnings
- Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions.
- Energy-method runtime can overestimate high-rate lead-acid performance due to Peukert and cutoff effects.
- Use the UPS and battery manufacturer runtime or constant-power discharge table for final selection.