Fire Alarm Battery Load Worksheet
Estimate fire-alarm standby and alarm amp-hour demand from project-specified currents, durations, and a user-entered capacity adjustment factor.
Load and duration details
Use the total system standby current from the approved load schedule or equipment data.
Enter the duration specified by the project documents and applicable authority.
Use the total alarm current for the operating condition specified by the system design.
Enter the duration specified by the project documents and applicable authority.
Use a factor established by the approved design basis or battery manufacturer. 100% applies no adjustment.
Estimated battery demand
The adjusted value is the calculated load demand multiplied by the factor you entered.
About this worksheet
Enter total standby current, standby duration, total alarm current, alarm duration, and a capacity adjustment factor from the approved design basis. The worksheet calculates the amp-hour contribution of each operating period and their adjusted total.
Enter system-level current values from the approved load schedule or equipment data. This worksheet does not calculate device loads or circuit voltage drop.
Method and assumptions
Standby demand (Ah) = standby current (mA) × standby duration (hours) ÷ 1,000. Alarm demand (Ah) = alarm current (mA) × alarm duration (minutes) ÷ 60 ÷ 1,000. Adjusted demand = (standby demand + alarm demand) × entered capacity factor ÷ 100.
The calculation treats each entered current as constant during its period. It does not model battery discharge curves, changing voltage, or product-specific capacity ratings.
Interpret the result
The primary result is the total amp-hour load after applying the factor you entered. It is not a battery selection or a pass/fail determination. The battery design must account for the listed equipment, discharge conditions, environmental limits, aging, recharge, and requirements adopted by the authority having jurisdiction.
FAQs
Where do the current values come from?
Use the approved system load schedule and the technical data for the exact fire-alarm control unit, notification appliances, and connected equipment. Include the operating condition required by the design.
Does this tool provide required standby or alarm durations?
No. Enter the durations from the approved design documents and applicable authority requirements. The worksheet does not determine which duration applies.
What does the capacity adjustment factor do?
It multiplies the unadjusted amp-hour demand by the percentage you enter. Use a value specified by the approved design basis or battery manufacturer; 100% applies no adjustment.
Does the result prove a battery is suitable?
No. Battery capacity depends on discharge rate, end voltage, temperature, age, listing, recharge requirements, and the exact system configuration. A qualified designer must verify the complete calculation and selected battery.
Sources
- Use the approved fire-alarm system load schedule, equipment listing, and manufacturer documentation for current values, battery ratings, discharge conditions, and adjustment factors.
- Use the applicable adopted fire-alarm requirements and authority direction to establish required operating durations and design conditions.