FireClass Prescient III - Standby Battery Requirements; 6.1 Battery Capacity Calculation; 6.2 Battery Replacement; 6.3 Battery Charging

EQUIPMENT: FIRECLASS Prescient III WRITTEN BY: RKP
PUBLICATION: OMFCPRES3IN CHECKED BY: AP
ISSUE No. & DATE: 0 02/02/12
PAGE 22 of 43
The charger output is designed for charging
Powersonic Valve Regulated Sealed Lead-Acid
batteries, which are characterised by a reducing
charge current when charged from a constant
potential source. It will not provide the maximum
charging current when the other power supply
outputs are fully loaded. The panel requires two 12V
batteries connected in series to produce 24V.
CONNECTING ONLY ONE 12 VOLT BATTERY
OR INCORRECT CONNECTION OF THE
BATTERIES WILL PERMANENTLY DAMAGE
THE PANEL AND THE BATTERY.
The battery charger circuit is temperature
compensated and relies on a Thermistor mounted
near the batteries to ensure that the correct
charging voltage is maintained. The Thermistor type
has been chosen to fit the profile of the Powersonic
VRLA batteries. Use of batteries by another
manufacturer is not recommended.
WARNING:
A fuse protects the internal power supply; always
replace this with the correct type and rating:
T5AH250V
(20mm fuse, 5A, HBC, Anti-surge, approved to
BS EN 60127 or equivalent.)
6. Standby Battery Requirements
6.1 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
(A)
X
Standby
Time
(H)
=
Battery
Capacity
Required
(Ah)
Mains Failed current is 0.060A plus ancillary
equipment e.g. if a Status Indicator draws 0.030A
then the total Mains Failed current is 0.090A.
Therefore over 24 hours the battery requirement
is:
0.090 X 24 = 2.16Ah
30 Minutes Alarm:
Alarm
Current
(A)
X
Alarm
Time
(H)
X
De-
rating
Factor
(1.5)
=
Battery
Capacity
Required
(Ah)
Alarm current is 0.160A plus the detector current
plus alarm and solenoid current plus ancillary
equipment e.g. if one detector is in alarm and
draws 0.030A, and the alarm load is 1.0A, and the
actuator load is 1.0A and a Status Indicator draws
0.040A then the total Alarm current is 2.23A.
Therefore over 30 Minutes the battery requirement
is:
(2.23 X 0.5) x 1.5 = 1.67Ah.
Therefore the total Battery requirement is:
2.16Ah + 1.67Ah = 3.83Ah
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 capacity required in this example
is:
1.25 x 3.83 = 4.79Ah
Note that the enclosure will only accommodate
two 12V batteries up to 12Ah capacity. Larger
sized batteries fitted in a separate enclosure are
not permitted.
6.2 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.
6.3 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 battery terminals on the internal
control board with the batteries connected. The
battery charger output should be 27.10V +/- 0.05V
@ 25
o
C (Thermistor value 15k.)
If the charger voltage requires adjustment, use an
insulated trimming tool to adjust the potentiometer
SVR1 on the Power Supply (see PSU layout
diagram in Figure 6 for location). See Table 3 for
recommended charge voltages.