Emergency-lighting battery energy equations
Fixture load energy is corrected for conversion loss, usable discharge, aging, temperature, and margin.
Eload = Pfixture × N × tEbattery = Eload × (1+margin)/(η × DOD × Faging × Ftemp)Ah = Ebattery/Vbatterywhere:
- Eload
- Energy delivered to emergency fixtures[Wh]
- Ah
- Required nominal battery capacity[Ah]
Battery energy does not prove emergency illuminance or legal compliance.
How to use the Emergency Lighting Battery Calculator
Estimate emergency-lighting battery Wh and Ah from fixture load, duration, efficiency, depth of discharge, aging, temperature, and design margin. 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. Fixture emergency input power is constant All fixtures operate for the full entered duration Battery voltage remains suitable for the emergency driver A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.
- Fixture emergency input power is constant
- All fixtures operate for the full entered duration
- Battery voltage remains suitable for the emergency driver
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. This sizes battery energy only; it does not prove emergency illuminance, uniformity, spacing or code compliance. Use listed emergency equipment and manufacturer discharge data at end-of-life and minimum temperature. 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.
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Assumptions
- Fixture emergency input power is constant
- All fixtures operate for the full entered duration
- Battery voltage remains suitable for the emergency driver
Important Warnings
- Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions.
- This sizes battery energy only; it does not prove emergency illuminance, uniformity, spacing or code compliance.
- Use listed emergency equipment and manufacturer discharge data at end-of-life and minimum temperature.