757
MAINTENANCE MANUAL
MAIN BATTERY SHUNT SEE MAIN BATTERY, BATTERY CURRENT MONITOR, E
MAIN BATTERY CHARGER SEE F BATTERY MAIN CONNECTOR BATTERY
BATTERY SHUNT MAIN
CURRENT MONITOR BATTERY
BATTERY CHARGER MAIN FORWARD EQUIPMENT AREA E FWD
TERMINAL COVER
OUTPUT TERMINALS
FWD
FORWARD EQUIPMENT AREA F Batteries Component Location Figure 1 (Sheet 3)
G38621
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757 MAINTENANCE MANUAL
(c) In the T-R mode, the charger acts as a regulated power supply at 27.75 volts dc with a current limit of 64 amps.
(2)
The following conditions will command the battery charger to start a constant current charge mode:
(a)
Input voltage is initially applied or interrupted for more than
0.5 second.
(b)
Battery voltage is less than 23 volts.
(c)
The charger has operated more than 0.5 second in the T-R mode and is switched to the charge mode.
(3)
The battery charger will shut down when any of the following conditions occur:
(a)
Input voltage less than 94 volts or greater than 134 volts.
(b)
An open in the battery interlock circuit.
(c)
Battery temperature above 145 degrees F (63 degrees C).
(d)
Loss of input power.
(e)
An internally caused overcurrent condition or inverter circuit unbalance.
(f)
A shutdown also occurs if the power connector is not connected to the battery when the charger is initially energized. The charger does not start unless the voltage sensed at the output terminals is above 4 volts.
(4)
The latched status and maintenance message MAIN BAT CHGR is displayed on the bottom display if any of the following conditions occur:
(a)
The interlock circuit is open.
(b)
The battery temperature is greater than 145 degrees F.
(c) The input power is lost. ú (5) AIRPLANES WITH CHARGER AND BATTERY LED's ON THE BATTERY CHARGER; ú There are two LED's (CHARGER and BATTERY) on the front panel of the ú battery charger. Both LED's are on when the battery and charger are ú in normal operation. If the battery is not in normal operation, ú then the BATTERY LED will be off. If the charger is not in normal ú operation, then the CHARGER LED will be off. If both LED's are off, ú then there is no 115 VAC input power to the charger.
(6) The main battery charger is located in the fwd equipment center, and the APU battery charger is located in the E6 rack.
C. Battery Shunts
(1)
A battery shunt is installed in the ground lead of the main battery to provide for battery current measurement. This measurement is sent to the EICAS computers.
(2)
A battery shunt is installed in the ground lead of the APU battery charger to provide APU battery charging current measurement. This measurement is sent to the EICAS computers.
D. Main Battery Relay
(1) The main battery relay K104 connects the hot battery bus to the battery bus. Switching occurs if the left main DC bus loses power or an autoland signal is present. Contacts on the relay provide mode control for the main battery charger. The relay is in main power distribution panel P6.
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757
MAINTENANCE MANUAL
E. Main Battery Transfer Relay
(1) The main battery transfer relay K106 connects the left main DC bus to the battery bus. The relay is in the P6 panel.
F. DC Under Voltage Sensing Relay
(1) The DC under voltage sensing relay K113 de-energizes the main battery transfer relay if left main DC bus voltage is low. The relay will open if voltage drops below 21.5 |.5 volts DC for 200 -400 milliseconds, or below 15 volts for 50 milliseconds. The relay will close when bus voltage exceeds 24.5 |.5 volts DC for 100 milliseconds. The relay is in the P6 panel.
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