Battery System - SAC SS-800AVS Manual

2.2.8 Battery System
The optional Battery Standby System automatically switches the
transmitter to battery power in case of AC power failure, and
automatically keeps the batteries charged under normal conditions.
The battery charger operates in two modes of operation during
charging, depending upon the state of charge of the batteries. The
charger initially operates in a constant current charging mode until
the battery voltage rises to an equalizing voltage of approximately
55 volts. The charger then switches to a voltage regulating mode
to maintain the battery voltage at a float voltage of approximately
52.4 volts (adjustable). A light emitting diode on the battery
charger PWB indicates whether the current regulating mode (LED OFF)
or voltage regulating mode (LED ON) is active. When the voltage
regulating mode is active, the battery float voltage can be adjusted
with R22.
During charging, power to the batteries is furnished from the
transmitter +50 volt supply with the voltage boosted i0 to 15 volts
by T1 and CRI-CR4. Charging current is regulated at approximately
2 amps maximum with current sensed across R7 and R8, and current
level controlled with QI, Q2 and Q3. Ul, RI7 and CRI0 latch the
charger into a current regulating mode. After the battery voltage
reaches an equalize voltage of about 55 volts, CRI0 reverse biases
and switches the charger to a voltage regulating mode with float
level voltage regulation through UI, Q6, Q2 and Q8. Float voltage
level is set for 52.4 volts for 24 cell lead acid batteries. For
Nickel Cadmium batteries, the normal float voltage is approximately
1.40 volts per cell or 53.2 volts for a 38 cell battery.
During discharge, current flows through CRI2, RTI, RT2 and K1 to
the transmitter. Battery voltage is monitored through CRI2. If
the battery voltage drops below approximately 38 volts, flip-flop
U3 is set, turning off Q4 and opening KI. Power is thus removed
from the transmitter. Flip-flop U3 is reset with power again being
applied to the transmitter when AC power is momentarily reapplied
or power is removed from the battery charger by turning off SI.
When AC power is present, Q4 and K1 are maintained in the OFF state.
SS-800AVS Southern Avionics
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