1. What is the Fire Alarm Battery Calculator?

The Fire Alarm Battery Calculator determines the minimum required battery capacity for fire alarm systems based on standby and alarm currents. It ensures compliance with safety standards that require 24 hours of standby power plus 5 minutes of alarm.

2. How Does the Calculator Work?

The calculator uses the following formula:

Where:

• Standby Current — Normal operating current of the system
• Alarm Current — Current drawn during alarm condition
• 24 hours — Required standby duration
• 0.083 hours — 5 minutes of required alarm time
• 1.25 — Safety factor (25% additional capacity)

Explanation: The calculation accounts for both normal operation and emergency conditions, with a safety margin for battery aging and temperature effects.

3. Importance of Proper Battery Sizing

Details: Correct battery sizing is critical for fire alarm system reliability. Undersized batteries may fail during emergencies, while oversized batteries increase costs unnecessarily.

4. Using the Calculator

Tips: Enter standby current in amps (normal operation current) and alarm current in amps (current during alarm condition). Values must be ≥0.

5. Frequently Asked Questions (FAQ)

Q1: Why is there a 1.25 multiplier?
A: The 25% additional capacity accounts for battery aging, temperature effects, and ensures reliable performance throughout the battery's life.

Q2: What are typical current values?
A: Standby current is usually 0.1-0.5A for small systems. Alarm current depends on connected devices but is often 1-5A.

Q3: Does this meet NFPA requirements?
A: Yes, this calculation meets NFPA 72 requirements for 24 hours standby plus 5 minutes alarm with safety margin.

Q4: Should I round up the battery size?
A: Yes, always round up to the next available standard battery size (e.g., 7Ah, 12Ah, 18Ah, etc.).

Q5: How often should batteries be replaced?
A: Fire alarm batteries should be replaced every 3-5 years or when capacity drops below 80% of rated capacity.