Fire Lite Battery Calculations

Battery Capacity Formula:

\[ \text{Battery Capacity (Ah)} = (\text{Fire Lite Standby A} \times 24 \text{ (h)} + \text{Alarm A} \times 0.5 \text{ (h)}) \times 1.25 \]

Battery Capacity (Ah):

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1. What is the Battery Capacity Calculation?

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

2. How Does the Calculator Work?

The calculator uses the following equation:

\[ \text{Battery Capacity (Ah)} = (\text{Standby Current} \times 24 \text{ hours} + \text{Alarm Current} \times 0.5 \text{ hours}) \times 1.25 \]

Where:

Standby Current — Normal operating current in amps (A)
Alarm Current — Current draw during alarm in amps (A)
24 hours — Required standby duration
0.5 hours — 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 30 minutes in alarm, with additional capacity for 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 to maintain operation during power outages, while oversized batteries may not charge properly.

4. Using the Calculator

Tips: Enter the standby current and alarm current in amps (A) as specified in the fire alarm system documentation. Both values must be non-negative.

5. Frequently Asked Questions (FAQ)

Q1: Why is there a 1.25 multiplier?
A: The 1.25 multiplier (25% additional capacity) accounts for battery aging, temperature effects, and other factors that reduce actual battery capacity over time.

Q2: What if my system has different duration requirements?
A: Adjust the 24 and 0.5 hour values in the calculation to match your specific code requirements or system specifications.

Q3: Should I round up the battery size?
A: Yes, always select a battery with the next higher standard Ah rating than your calculated value.

Q4: Does this account for battery type?
A: This calculation is for sealed lead-acid batteries typically used in fire alarm systems. Other battery types may require different calculations.

Q5: How often should batteries be tested?
A: NFPA 72 requires annual battery discharge testing under load to verify capacity.