1. What is Fire Alarm Battery Calculation?

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

2. How Does the Calculator Work?

The calculator uses the standard fire alarm battery capacity formula:

Where:

• \( Design\ Current\ Standby \) — Current drawn during normal operation (A)
• \( Design\ Alarm \) — Current drawn during alarm condition (A)
• 24 — Hours of standby operation required
• 0.25 — Hours of alarm operation required (15 minutes)
• 1.1 — Safety factor (10% additional capacity)

Explanation: The calculation ensures the battery can power the system for 24 hours in standby plus 15 minutes in alarm, with 10% extra capacity.

3. Importance of Proper Battery Sizing

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

4. Using the Calculator

Tips: Enter the standby current and alarm current in amps. Both values must be zero or positive. The result shows the minimum required battery capacity in ampere-hours (Ah).

5. Frequently Asked Questions (FAQ)

Q1: Why 24 hours standby and 15 minutes alarm?
A: These are standard requirements in most fire codes to ensure system operation during extended power outages and sufficient time for evacuation.

Q2: What's the purpose of the 1.1 multiplier?
A: The 10% safety factor accounts for battery aging, temperature effects, and manufacturing tolerances.

Q3: Should I round up the battery size?
A: Yes, always select the next standard battery size above the calculated value.

Q4: Does this account for battery temperature effects?
A: No, for installations in extreme temperatures, additional derating factors may be needed.

Q5: Is this calculation suitable for all fire alarm systems?
A: This covers typical systems, but specialized systems may have different requirements.