Standby Battery Calculation Guide - XFP XFP501E/X Engineering Manual

XFP 16 ZONE ANALOGUE ADDRESSABLE FIRE ALARM PANEL

STANDBY BATTERY CALCULATION GUIDE

The standby time of the fire alarm panel after the Mains has failed depends on the quiescent
loading of the panel, the alarm load of the panel, and the capacity of the batteries.
To determine the capacity of batteries required for any given stand-by period, the following
formula should be used:
The multiplier 1.25 is present to account for lost capacity over the life of the batteries.
H = Number of hours standby required
P = The quiescent current of the panel = 0.042A
This value is with the Mains failed, beeper silenced and the Supply Present and General Fault
indicators lit. If there are other quiescent drains on the Panel then these must be added in.
Z = The total quiescent current of all zone devices
As a guideline, the average quiescent current addressable devices is typically 0.00025A (250µA).
To obtain accurate figures consult the device manufacturers' own specifications.
A = The total alarm current of the panel sounders (plus any other devices connected to other alarm
outputs).
T = The amount of time in hours required for the alarm (most commonly being half an hour).
Example 1:
The panel has 50 devices each consuming 250µA each, 15 sounders at 8mA each, the required
standby time is 24 hours, and the required alarm time is 0.5 hours.
Z = 50 x 0.00025 = 0.0125A
P = 0.042A
A = 15 x 0.008= 0.12A
H = 24
T = 0.5
Standby Time in Ah = 1.25 x [(0.5 x 0.12) + 24 x (0.0125 + 0.042)] = 1.71Ah
Therefore, batteries with at least 1.71Ah capacity are required.
Example 2:
The panel has 100 devices each consuming 250µA each, 40 sounders at 20mA each connected to
the panel sounder circuits, the required standby time is 24 hours, and the required alarm time is
0.5 hours.
Z = 100 x 0.00025 = 0.025A
P = 0.042A
A = 40 x 0.02 = 0.8A
H = 24
T = 0.5
Standby Time in Ah = 1.25 x [(0.5 x 0.8) + 24 x (0.025 + 0.042)] = 2.51Ah
Therefore, batteries with at least 2.51Ah capacity are required.
XFP ENGINEERING MANUAL • Approved Document No. DFU1200510 Rev 3 • Page 35 of 36
S t a n d b y T i m e i n A h = 1 . 2 5 x [ ( T x A ) + H x ( P + Z ) ]