1. What is Battery Capacity Calculation?

The battery capacity calculation determines the required ampere-hour (Ah) rating for a fire alarm system battery to ensure proper operation during both standby and alarm conditions, with an additional safety factor.

2. How Does the Calculator Work?

The calculator uses the following equation:

Where:

• Standby Current — Current drawn by system in normal operation (amps)
• 24 hours — Required standby duration
• Alarm Current — Current drawn during alarm condition (amps)
• 0.083 hours — 5 minutes required alarm duration
• 1.25 — Safety factor (25% additional capacity)

Explanation: The calculation ensures the battery can power the system for 24 hours in standby plus 5 minutes in alarm, with 25% extra capacity for aging and temperature effects.

3. Importance of Battery Calculation

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

4. Using the Calculator

Tips: Enter standby and alarm currents in amps. Values must be non-negative. Typical values range from 0.1-2A for standby and 0.5-5A for alarm.

5. Frequently Asked Questions (FAQ)

Q1: Why is there a 1.25 multiplier?
A: The 1.25 factor (25% extra capacity) accounts for battery aging, temperature effects, and manufacturing variations.

Q2: What if my system has different duration requirements?
A: Adjust the 24h and 0.083h values in the formula to match your specific code requirements.

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

Q4: Does this account for battery type?
A: This calculation is for lead-acid batteries. Lithium batteries may have different characteristics.

Q5: What about multiple alarm devices?
A: The alarm current should be the total current of all devices that may activate simultaneously.