Ampac SP Series, Installation, Commissioning & Operation

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FireFinder
™
Installation Commissioning & Operation
Page 95
24 Battery Capacity Calculation
INTRODUCTION
The standby power source capacity, or battery capacity, determines how long the system will continue
to operate in the event of the loss of the primary power source. It therefore becomes necessary to
calculate the battery and hence power supply / battery charger capacity required for each installation.
The following calculator has been designed to determine the required capacity to meet the required
standards. Should an existing panel be expanded the required battery and power supply capacity
should be recalculated to ensure the panel continues to operate within the required standards.
The standards considered in this document are:
AS1603/4428 EN54 NZS4512 UL72 MS1404 GB4717
DESCRIPTION
Enter the number of units listed in the left hand column which go to make up the panel, complete
the multiplication to obtain the quiescent current then multiply by the standby and alarm hours
required by the standard.
POWER SUPPLY RATING
The minimum Power Supply Rating ( 4 ) is obtained by calculating the manufacturers
recommended battery charge current [ see Note ] ( 1 ) then adding the quiescent current of the
entire system ( 2 ) and the alarm current ( 3 ).
1. Battery Capacity (AH) (
determined from Calculator
) = Amps
24 x 0.8
2. Add Quiescent Current of the System ( Iq) = Amps
3. Add the extra current that is drawn when in alarm ( Ia ) = Amps
4. Minimum Current Rating of Power Supply is = Amps
☞
Note: Point 1 Battery Capacity
The capacity of the battery shall be such that in the event of failure of the primary power source the
batteries shall be capable of maintaining the system in normal working (quiescent) condition for at
least 24 h, after which sufficient capacity shall remain to operate two worst case AZFs and
associated ACFs for 30 min.
When calculating battery capacity, allowance shall be made for the expected loss of capacity over
the useful life of the battery. A new battery shall be at least 125% of the
calculated capacity requirements, based on a loss of 20% of its capacity over the useful life of the
battery.
☞
Note: Where the fire control station will not receive the system's total power supply failure signal,
the battery should have sufficient capacity to maintain the system for 96 h.