Direct Answer

Using the source inputs, the calculated battery capacity is 14.22 Ah; the source selects the next standard size as an 18 Ah battery set. Final sizing must be checked against OEM requirements, ageing/derating and applicable codes.

At a Glance

Standby / alarm current	0.45 A / 2.10 A
Standby / alarm duration	24 h / 0.5 h
Design factor	1.20
Calculated / selected capacity	14.22 Ah / 18 Ah

Technical Content

Fire Alarm Battery Backup Calculation

1. Purpose

To determine the minimum battery capacity required to support a Fire Alarm Control Panel during standby and alarm conditions in accordance with applicable standards and manufacturer requirements.

2. Engineering Objective

To calculate battery ampere-hour (Ah) capacity for reliable operation during mains power failure.

3. Applicable Standards

4. Design Inputs

5. Assumptions

Battery is new, fully charged and lead-acid type. Manufacturer derating and ageing factors shall be verified.

6. Formula(s)

Battery Capacity (Ah) = [(Is × Ts) + (Ia × Ta)] × Design Factor

7. Variables Explained

Is=Standby current; Ia=Alarm current; Ts=Standby time; Ta=Alarm time.

8. Step-by-Step Calculation

Standby Ah = 0.45×24 = 10.80 Ah Alarm Ah = 2.10×0.5 = 1.05 Ah Raw = 11.85 Ah Final = 11.85×1.20 = 14.22 Ah Select next standard battery size: 18 Ah.

9. Worked Engineering Example

A panel drawing 0.45 A standby and 2.10 A alarm requires 14.22 Ah. An 18 Ah battery set satisfies the requirement.

10. Engineering Output

Required Capacity: 14.22 Ah Recommended Battery: 18 Ah

11. Design Considerations

Consider temperature, battery ageing, charger capacity and OEM recommendations.

12. Common Design Mistakes

Ignoring design factor, incorrect standby duration, undersized batteries, no ageing allowance.

13. Practical Site Notes

Perform discharge testing and replace batteries at recommended intervals.

14. Limitations

Final battery sizing shall comply with OEM documentation and applicable codes.

15. Related Engineering Systems

FACP, Battery Charger, Power Supply, NAC Circuits.

16. Cross References

Related FAQ: Fire Alarm Battery Backup Related White Paper: VEP-001 Related Diagram: ED-006

17. SEO Meta Title

Fire Alarm Battery Backup Calculation | EC-006

18. SEO Meta Description

Calculate fire alarm battery backup capacity with a worked engineering example.

19. URL Slug

ec-006-fire-alarm-battery-backup-calculation

20. Keywords (15)

Fire Alarm Battery, Battery Calculation, NFPA72, IS2189, Ampere Hour, FACP, Standby Current, Alarm Current, Fire Protection Engineering, Engineering Calculation, EPC, Consultant, Battery Sizing, Fire Alarm Design, Power Supply

21. AI Search Summary

Fire alarm battery capacity is calculated by adding standby and alarm ampere-hour requirements and applying a design factor. In this example, the required capacity is 14.22 Ah, so an 18 Ah battery is selected.

Source Tables

Standard		Description
NFPA 72		National Fire Alarm and Signaling Code
IS 2189		Fire Detection & Alarm Systems
NBC India Part 4		Fire & Life Safety
OEM Manual		Panel battery sizing
Parameter	Symbol	Value	Unit
Standby Current	Is	0.45	A
Alarm Current	Ia	2.10	A
Standby Duration	Ts	24	h
Alarm Duration	Ta	0.5	h
Design Factor	Df	1.20	–

Frequently Asked Questions

What battery capacity does the example calculate?

The source calculates 14.22 Ah and selects an 18 Ah battery set.

Is the selected capacity universally suitable?

No. Check OEM sizing, temperature, ageing, derating, charger capacity and applicable project requirements.

SEO & Publishing Details

SEO title: Fire Alarm Battery Backup Calculation | EC-006

Meta description: Calculate fire alarm battery backup capacity with a worked engineering example.

URL slug: ec-006-fire-alarm-battery-backup-calculation

Keywords: Fire Alarm Battery; Battery Calculation; NFPA 72; IS 2189; Ampere Hour; FACP; Standby Current; Alarm Current; Fire Protection Engineering; Engineering Calculation; EPC; Consultant; Battery Sizing; Fire Alarm Design; Power Supply