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Application, Installation & Commissioning Doc. version 2
5.2 Standby Battery Requirements
FIRECLASS Prescient III
5.2
Standby Battery Require-
ments
5.2.1
Battery Capacity Calculation
The usual requirement for standby batteries is 24 Hours
standby, plus 30 Minutes in Alarm.
Use the following as a guideline when calculating your
requirements.
24 Hours Standby
Mains Failed current is 0.060 A plus ancillary equipment
e.g. if a Status Indicator draws 0.030 A then the total
Mains Failed current is 0.090 A.
Therefore over 24 hours the battery requirement is:
0.090 X 24 = 2.16 Ah
30 Minutes Alarm
Alarm current is 0.160 A plus the detector current plus
alarm and solenoid current plus ancillary equipment e.g.
if one detector is in alarm and draws 0.030 A, and the
alarm load is 1.0 A, and the actuator load is 1.0 A and a
Status Indicator draws 0.040 A then the total Alarm cur-
rent is 2.23 A.
Therefore over 30 Minutes the battery requirement is:
(2.23 X 0.5) x 1.5 = 1.67 Ah
.
Therefore the total Battery requirement is:
2.16 Ah + 1.67Ah = 3.83 Ah
Use batteries with a rating of at least 25% more than
the capacity required. This is to allow for deterioration of
the batteries during use. So the minimum battery capac-
ity required in this example is:
1.25 x 3.83 = 4.79 Ah
5.2.2
Battery Replacement
The useful life of the standby batteries in this panel is
three years. The batteries must be replaced after this
time. To ensure this, when first installed, the battery
should be clearly labelled with the date of installation
and scheduled replacement date.
5.2.3
Battery Charging
The battery charger voltage is set during manufacturing
and should not require adjustment. The output voltage
can be verified by measuring the voltage across the bat-
tery terminals on the internal control board with the bat-
teries connected. The battery charger output should be
27.10 V +/- 0.05 V @ 25
o
C (Thermistor value 15 k.)
If the charger voltage requires adjustment, use an insu-
lated trimming tool to adjust the potentiometer SVR1 on
the Power Supply (see PSU layout diagram in Fig. 6 for
location). See Table 7 for recommended charge volt-
ages.
Mains Failed
Current
(A)
X Standby
Time
(H)
=
Battery
Capacity
Required
(Ah)
Alarm
Current
(A)
X Alarm
Time
(H)
X
De-rating
Factor
(1.5)
= Battery
Capacity
Required
(Ah)
Battery Capacity
Note that the enclosure will only accommo-
date two 12 V batteries up to 12 Ah capacity.
Larger sized batteries fitted in a separate
enclosure are not permitted.
