Bc-35 - Fire Alarm Resources

Fire Safety
The SIEMENS Model BC-35 battery charger/transfer
module complies with UL Standard 864. The module is
designed to monitor the battery charge status and alert
appropriate personnel when the batteries may not have the
standby power capacity required by NFPA Standard 72
Local, Municipal Tie, Remote Station, or Proprietary.
The BC-35 charging circuit provides a charging current
only if the voltage of the batteries being used is
between 18.3 VDC and 27.7 VDC. If the battery voltage is
out of this range, the BC-35 will automatically cut off its
charging circuit.
CAUTION: Disconnect the system power input before
installing the BC-35 and/or BE-35 cable connections.
The BC-35 module has a trouble signal for both high and
low battery conditions. A trouble condition occurs:
During normal AC operation when the instantaneous
or constant voltage across the battery is more than
30 volts peak or is less than 24 volts.
During the battery backup operation when the
instantaneous or constant voltage across the battery
is more than 30 volts peak or is less than 21 volts.
Siemens Building Technologies, Inc.
8 Fernwood Road
Florham Park, New Jersey 07932
P/N 315-086767-4
Siemens Building Technologies, Ltd.
2 Kenview Boulevard
Brampton, Ontario L6T 5E4 CN
When the battery trouble signal activates because of a low
battery voltage, it indicates that the batteries may have
inadequacies that will prevent the BC-35 from providing the
standby power capacity required to meet national and local
codes. When the signal activates because of a high battery
voltage, it indicates one of the following: 1) BC-35 malfunction, 2) poor battery terminal connections, or 3) a battery
that has an unacceptable high internal resistance.
It is recommended that the batteries be charged prior to
installation, if necessary. A voltage check of the batteries
should be performed to ensure that the BC-35 charging circuit will begin charging. Follow Steps 1 and 2 below. Step 2
may also be used to troubleshoot the BC-35 when a trouble
condition is indicated.
Step 1
Test the batteries connected to the BC-35 module.
a. Remove the battery leads.
b. Test the open battery voltage; it should be between
22 and 27 VDC.
c. Reconnect the battery and test it under a load condition. If possible, remove the AC power from the
system and measure the battery voltage. Activate the
audible devices and again measure the battery
voltage. Under both conditions, the minimum
acceptable battery voltage is 21 VDC.
d. If it is not possible to test the batteries as previously
noted, utilize a simulated load. For example, with the
batteries disconnected, a 12 ohm, 50 watt resistor
should be placed momentarily (2-4 seconds) across
the 24 volt battery connections. Measure the battery
voltage under this loaded condition. Again, the
minimum acceptable voltage is 21 VDC.
Replace the batteries if the results of b, c, or d above are
not acceptable.
Step 2
Verify that the BC-35 is providing a charging current.
a. If an MM-35 is being used in conjunction with a BC-35,
check the meter and verify that a current is being
supplied to the batteries either in a constant or a
pulsed mode.
b. If no MM-35 is being used, place an analog VOM meter
with a 10 amp scale in series with the batteries connected to the BC-35 module. If the batteries are being
charged, the VOM meter will indicate a constant
current or pulsed current is being provided to the
A constant charging current or pulsed charging current
is displayed if the battery voltage is between 18.3 VDC
and 27.7 VDC. Once the battery is fully charged, a
pulsed charging current is present on a periodic basis.
The time between pulses is determined by the rate of
discharge due to the internal circuitry of the charger
and the ability of the individual battery to accept and
maintain the charge condition. The constant charge
current is between .5 and 1.5 amps for the BC-35 and
increases proportionally if BE-35 modules are used.
On initial system startup, when the battery charger is
functional, but the battery trouble indicator remains on,
the batteries may not have had time to properly
charge—as much as 24 hours may be necessary for
charging. After charging for 24 hours with the charging
current as described above, and the BC-35 trouble
signal still on:
1) If less than 24V is present across the battery:
(a) Batteries are not accepting the charge
(b) Battery capacity is too large for the BC-35
and the number of BE-35s being used
2) If more than 30V is present across the battery:
(a) Batteries used have high internal impedance
(b) BC-35 is not shutting off the charge state at
the required voltage point
If the BC-35 is not providing a charging current, test
pin 1 of the P1 plug on the BC-35 module in reference
to the negative side of the power supply. If there are no
volts at this point, replace the BC-35 module. If there
are more than 2 VDC at this point, and no alarm is
present, replace the CP-35 panel.
This information is provided to assist you in diagnosing
relatively routine problems. There may be extenuating
circumstances involved which are not covered here. If
further assistance is needed, please contact your Regional
Engineer or the Siemens Building Technologies, Inc.
Technical Support Group.
WARNING: The BC-35 has been factory set for the
batteries specified. Any alteration or
adjustment to this module will void both
the UL listing and the Manufacturer’s
Warranty and may cause damage to the
P/N 315-086767-4
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