Battery Supervision; Stand-By Battery Calculations - Bosch 24VDC Operation And Installation

Battery Supervision

The D9142F supervises the batteries for both missing and low battery conditions. To maintain battery lead supervision,
and optimum performance, do not parallel additional batteries on to the power supply.
When the battery is disconnected or the battery voltage drops into the 22 - 24 VDC range, the red Trouble LED lights and
the power supply triggers the Low Battery Trouble output.
When battery is restored and the voltage returns to the 24.2 - 26.5 VDC range, the red Trouble LED is turned off and the
Low Battery Trouble output is reset.
Calculating Standby Power Requirements
Commercial Fire Alarm Systems typically require either 24 or 60 hours of stand-by time. Table 1 is designed to assist
you in determining the battery amperage needed to achieve the desired standby time or current output.
Selecting the Correct Batteries
Selecting the correct batteries for the system depends on the total continuous current draw of all devices, the amount of
stand-by time required, the amount of intermittent current draw (in alarm) needed and finally the time it takes to recharge
the batteries.
Table 1 shows the amount of current (at 24 VDC) that can be drawn for a given battery selection. The calculations used
to create this table include the intermittent current required for five minutes of 3A bell time at the end of the standby
period. When the summary trouble relay is used, subtract 0.02 amps from the available standby current you select from
the table.
Example: 7 amp hours of battery capacity (two 12v 7 Ah, D126 batteries installed) provide 24 hours of standby time,
when drawing no more than 0.135 A from the supply continuously. 7 amp hours also provide up to 3 A of alarm power
for indicating devices for five minutes at the end of the stand-by period.
F01U036364-03
Table 1
D9142F Operation and Installation
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