1. What is the Fire Alarm Battery Capacity Calculation?

The fire alarm battery capacity calculation determines the minimum battery size required to power a fire alarm system during both standby and alarm conditions, with an appropriate safety margin.

2. How Does the Calculator Work?

The calculator uses the following equation:

Where:

• Standby Load — Current drawn during normal operation (amps)
• Alarm Load — Current drawn during alarm condition (amps)
• 24 hours — Required standby duration
• 0.083 hours (5 minutes) — Required alarm duration
• Safety Margin — Typically 1.25 (25% extra capacity)

Explanation: The equation calculates the total energy needed for 24 hours of standby plus 5 minutes of alarm, then adds a safety factor.

3. Importance of Proper Battery Sizing

Details: Proper battery sizing ensures the fire alarm system remains operational during power outages and can activate all alarm devices when needed. Undersized batteries may fail when needed most.

4. Using the Calculator

Tips: Enter the standby and alarm currents in amps from your fire alarm panel specifications. The safety margin is typically 1.25 but may be adjusted based on local codes or specific requirements.

5. Frequently Asked Questions (FAQ)

Q1: Why 24 hours standby and 5 minutes alarm?
A: These are common requirements in fire codes (NFPA 72 in the US) for central station monitored systems.

Q2: Can I use this for other battery calculations?
A: This is specific for fire alarm systems. Other applications may have different requirements.

Q3: What if my system has different duration requirements?
A: Adjust the hours in the calculation accordingly (e.g., 60 hours for non-monitored systems).

Q4: Should I round up the battery size?
A: Yes, always round up to the next available standard battery size.

Q5: Does temperature affect battery capacity?
A: Yes, cold temperatures reduce capacity. You may need additional margin in cold environments.