Determining the Standby Battery Capacity
This section provides guidelines for determining the standby battery rating. For power supply applications that do
not include fire alarm equipment, alar m current is the dynamic current present during operation of the power
supply. Standby current is the static curr ent present when the power supply is not operating an alarm.
Battery Rating Equation
The equation below describes the method for determining the amp hour rating of the standby batteries:
Battery Rating = ( Battery De- Rating Factor ) x [ ( Standby amp hours ) + ( Alarm amp hours )]
OR
Battery Rating = ( Battery De- Rating Factor ) x [ ( 24 hours x Standby-Current ) + ( 5 Minutes x Alarm Current)]
where the batt ery de-rating factor = 1.2 and 5 minutes = 5 / 60 minutes = 1/12 = .0833 hours
To determine the amp hour rating of standby batteries:
1. Record the standby current of the power supply.
2. Record the standby current of the fire control panel. This current includes the LCD Main Processor Board,
the Main Back Board, System A Panel Module, and System B Panel Module. It does not include current of
the power supply and circuit boards in Slots C through F.
3. Record the standby current of circuit boards populating Slots C through F.
4. Record the standby current of SLC, NAC, and auxiliary devices.
5. Total standby currents.
6. Record the alarm cur rent of the power supply.
7. Record the alarm cur rent of the fire control panel. This current includes the LCD Main Processor Board,
the Main Back Board, System A Panel Module, and System B Panel Module. It does not include current of
the power supply and circuit boards in slots C through F.
8. Record the alarm cur rent of circuit boards populating slots C through F of the panel.
9. Record the alarm cur rent of SLC, NAC, and auxiliary devices.
10. Total alarm currents.
11. Multiply the tot al standby current with the standby-time of 24, 48, or 72 hours to provide the result in amp
hours.
12. Multiply the tot al alarm current with the alarm time 5 or 15 minutes to provide the result in amp hours.
13. Combine the sum of amp hours for total standby and alarm.
14. Determine the minimum required amp hour capacity of the standby battery by mu ltiplying the combined
Amp hours with the 1.2 de-rating factor.
Appendix C: Calculations
SHIELD Fire, Safety & Security Ltd
Aura Fire Alarm Control Panel Installation Manual
Version 1.00 | June 2019 | MAN-1431VS
Page 144
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