Installation manual

SAFEPATH Manual Sheet 73 of 78
Rev. C April 1999
Supervised Audio System Battery Charger Module (SABC)
The supervised audio system battery charger module (SABC) provides battery charging and supervision as well as AC power
supervision for the SAFEPATH system.
The SABC monitors three parameters: AC input power, battery wiring and battery voltage. When a low AC input power condition is
detected, the PWR LOW indicator is illuminated. When a battery wiring open condition is detected, the BAT OPEN indicator is
illuminated. When a low battery voltage condition is detected, the BAT LOW indicator is illuminated. See Figure 37 for the indicator
locations on the SABC.
The battery charger operates on the dual voltage charging principal, thereby achieving the highest possible level of charge in the
shortest amount of time while maintaining battery reliability. The charging circuit is enabled when the AC voltage is within the
specified range, the SAFEPATH system is not in alarm, and the battery voltage is above the charge enable threshold level.
When charging begins, the current will be limited to the fast charge rate. As the batteries charge, the terminal voltage increases.
The terminal voltage is eventually limited to the overcharge voltage level and the charging current begins to drop. When the
charging current drops below the overcharge termination current the float state is entered. At this time the batteries are
approximately 90% charged.
There are three fuses on the printed circuit board, F1, F2, and F3. F1 is the fuse for the battery wiring. Fuse F2 is the DC supply
fuse which directly powers the charging circuitry. F3 is the fuse for the AC input voltage supervision circuitry. See Figure 37 for fuse
locations.
Fuse Rating
F1 30A
F2 10A
F3 0.5A
Nominal Specifications:
AC Supply Voltage 120VAC
DC Supply Voltage Range 20.4VDC to 26.4VDC
DC Supply Current @ 24VDC, Bulk Charge Rate 3.7A
Fast Charge Rate Current @ Vbat = 26VDC 2.6A
Overcharge Voltage 28.9VDC
Overcharge Termination Current 469mA
Float State Voltage 27.3VDC
Charge Enable Voltage 20VDC
Battery Type Lead Acid Starved Electrolyte
Nominal Battery Voltage 24VDC
Maximum Battery Capacity 72AH
Figure 37.
Supervised Audio System Battery Charger Module