1. What is Standby Battery Capacity?

Standby battery capacity is the amount of energy storage required to maintain a fire alarm system during power outages. It ensures the system remains operational for the required standby period with an appropriate safety margin.

2. How Does the Calculator Work?

The calculator uses the following equation:

Where:

• Standby Current — Quiescent current draw of the fire alarm system in amps
• Standby Time — Required backup duration in hours
• Safety Margin — Factor to account for battery aging, temperature effects, etc. (typically 1.2-1.5)

Explanation: The equation calculates the minimum battery capacity needed to power the system during an outage, with additional capacity to account for real-world conditions.

3. Importance of Proper Sizing

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

4. Using the Calculator

Tips: Enter the system's standby current in amps, required standby time in hours, and safety margin (typically 1.2 for 20% margin). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is typical standby current for fire alarms?
A: Most fire alarm control panels draw between 0.5-2 amps in standby, but consult manufacturer specifications for exact values.

Q2: What standby time is required by code?
A: NFPA 72 typically requires 24 hours of standby plus 5 minutes of alarm, but local codes may vary.

Q3: Why include a safety margin?
A: Batteries lose capacity over time and with temperature fluctuations. The margin ensures reliable operation throughout the battery's life.

Q4: Should I round up the calculated capacity?
A: Yes, always select the next available standard battery size above your calculated value.

Q5: Does this account for alarm current?
A: No, this calculates standby capacity only. Alarm current requirements should be calculated separately and added to the total.