SIMPLICITY PLUS INSTALLATION MANUAL
Approved Document No: GLT.MAN-107
PAGE 44
Issue 3.16 Author: NRPJ Date: 21/09/2017
20.1 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]
I
Qz
= Quiescent current in amps of all detection zones. e.g. Addressable optical detector 0.00048 Amp
(480 μA)
Typical Example:
A system comprises of 80 Addressable Optical detectors, 30 Sounder bases and 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
T
SBY
= 24 Hr
I
QP
= 0.105A (Quiescent current for panel)
I
QD
= 80 x 0.00048 =0.0384 A [the quiescent current for an Addressable Optical detector is 480 μA)
I
Qs
= 30 x 0.0004 =0.012 A [the quiescent current for an Addressable sounder is 400 μA)
I
Alm-snd
= 30 x 0.004 =0.12A
I
AP
= 0.115A
Therefore using the equation:
Battery Size (Standby time in Amp Hours) = 1.25 x [(Df x T
ALM
x I
ALM-snd
+I
AP
)+ (T
SBY
x (I
QP
+ I
QD
+ I
Qs
))]
(DF is a derating factor (typically = 2) used when a battery has to supply a high current load)
Battery Size (Standby time in Amp Hours) = 1.25 x [(2 x 0.5 x (0.115+0.12)) + (24 x (0.105 + 0.0384 + 0.012))]
Battery Size (Standby time in Amp Hours) = 1.25 x [0.235 + (24 x 0.1554)]
Battery Size (Standby time in Amp Hours) = 1.25 x [0.235 + 3.7296]
Battery Size (Standby time in Amp Hours) = 1.25 x 3.9646
Battery Size (Standby time in Amp Hours) = 4.95575 Amp Hours
This system would require a minimum of 4.96 Ah batteries, so we would recommend using 7Ah batteries .
