PREMIER M PLUS INSTALLATION MANUAL
Approved Document No: GLT.MAN-111
PAGE
16
Issue : 2.8 Author: NJ Date: 23/07/2012
11. STANDBY BATTERY CALCULATION
In order to calculate the standby battery size required, the following formula can be used:-
Battery Size (Standby time in Amp Hours) = 1.25 x [(T
ALM
x I
ALM
) + (T
SBY
x (I
QP
+ I
QZ
))]
Where:
T
ALM
= Maximum time in hours required for the alarm [½ hour is most common time]
I
ALM
= Total Alarm Current in amps for all alarm devices connected to the alarm circuits
T
SBY
= Standby time in hours for the system after mains failure [normally 24, 48 or 72 hr]
I
QP
= Quiescent current in amps of control panel in fault condition [because of mains failure]
IQZ
= Quiescent current in amps of all detection zones. Eg Ion detector 0.00005 Amp (50 μA),
Optical Detector = 0.0001 Amp (100 μA)
Typical Example:
A system comprises of 24 zones. Each zone has 20 smoke detectors. 10 bells are connected to each of the common sounder circuit.
The required standby is 24 hours. It will need to operate in alarm for ½ hour.
Calculate the battery size required.
T
ALM
= 0.5 Hr
I
ALM
(panel) = 0.205mA
I
ALM
= (4x10) x 0.025 =1.0A [This typical bell current is 25 mA. Most alarm Devices show their operating current on their instruction
sheet. Typical sounders will take less current]
T
SBY
= 24 Hr
I
QP
= 0.105A
I
QZ
=24 x 20 x 0.00006 =0.0288A [the quiescent current for a typical optical detector is 60 μA
Therefore using the equation:
Battery Size (Standby time in Amp Hours) = 1.25 x [(T
ALM
x I
ALM
) + (T
SBY
x (I
QP
+ I
QZ
))]
Battery Size (Standby time in Amp Hours) = 1.25 x [(0.5 x (0.205+1.0)) + (24 x (0.105 + 0.0288))]
Battery Size (Standby time in Amp Hours) = 1.25 x [(0.5 x 1.205) + (24 x 0.1338)]
Battery Size (Standby time in Amp Hours) = 1.25 x [0.6025 + 3.2112]
Battery Size (Standby time in Amp Hours) = 1.25 x 3.8137
Battery Size (Standby time in Amp Hours) = 4.76 Amp Hours
This system would require a minimum of 4.76Ah batteries, so we would recommend using 7Ah batteries (the nearest convenient
size).
*On a system with a heavier load, it may be necessary to use larger batteries. This may require a separate battery box to hold the
batteries.
