Emergency Lighting Battery Runtime Checker
Estimate nominal battery capacity and end-of-life energy duration for a stated emergency load. Verify actual discharge curves, temperature, cut-off voltage and emergency photometry.
Screening only. This tool does not classify hazardous areas or approve a product, installation or safety system. Use the applicable project requirements, manufacturer data and exact certificate conditions.
Method & limits
Required rated Ah = load W × duration h ÷ (voltage V × DoD × efficiency) × aging factor. Estimated end-of-life duration = rated Ah ÷ aging factor × V × DoD × efficiency ÷ load W. Percentages are converted to fractions. This constant-energy model omits discharge-rate effects, temperature dependence, BMS limits and voltage variation; do not size a safety system from this estimate alone.
Frequently asked questions
What does PASS mean?
The calculated duration equals or exceeds the selected target under the entered assumptions. It is not emergency-lighting compliance approval.
Are the defaults battery specifications?
No. The 80%, 85% and 1.25 values are editable planning assumptions. Replace them with accepted design and battery data.
Why can real runtime differ?
Discharge rate, cold conditions, aging, cut-off voltage, driver behavior and battery chemistry affect usable energy.
Does three hours always apply?
No. Duration depends on the applicable rules and building strategy. The 1 h and 3 h presets do not replace project requirements.
Does sufficient Ah prove sufficient illuminance?
No. Emergency output, distribution, escape-route illuminance and test requirements must be assessed separately.
Sources & verification
Source and calculation review: 2026-11-05. Reference methods do not replace the edition adopted for your project.