(2)
AIRPLANES WITH EXTENDED STANDBY POWER; The battery current monitors are installed around the ground lead of the main and APU batteries. The monitor magnetically senses the magnitude and direction of battery current. The monitor is located next to the battery.
(3)
AIRPLANES WITH 30-MINUTE STANDBY POWER; If battery discharge current is more than the monitor's threshold current, the current monitor provides a ground to the DISCH light on the standby power control panel, causing the light to come on. The current monitor also supplies a ground to EICAS causing the MAIN BAT DISCH advisory message to be shown on the upper display.
(4)
AIRPLANES WITH EXTENDED STANDBY POWER; If the main or APU battery discharge current is more than the monitor's threshold current, the current monitor provides aground to the MAIN BAT DISCH light or APU BAT DISCH light on the standby power control panel, causing the light to come on. The current monitor also supplies a ground to EICAS causing the MAIN BAT DISCH or APU BAT DISCH advisory message to be shown on the upper display.
(5)
The threshold current is 4 amps for current monitor which has part number 1566-1-1. For current monitor which has part number 1566-1-2, the threshold current is 6 amps.
H. Main Battery Charger Disable Relay
(1) The main battery charger disable relay (MBCDR) K115 switches AC power from the ground service bus to the battery charger inputs. The MBCDR is located in main power distribution panel P6.
I. Main Battery Charger Detection Relay
(1) The main battery charger detection relay K10425 is a time delay relay and is controlled by the main battery current monitor and the main/APU battery charger detection enable relay K10424. When relay K10425 is energized, the main battery charger shutdown detection circuit is connected to EICAS. Relay K10425 has a dropout time delay of 750 milliseconds and remains latched until electrical power is removed from the airplane or until the STBY POWER switch on the standby power control panel is set to BAT. Relay K10425 is in the P6 panel.
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24-31-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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757
MAINTENANCE MANUAL
J. APU Battery Charger Interlock Relay
(1) The APU battery charger interlock relay (ABCIR) K116 connects AC power from the ground service bus to the battery charger inputs. The ABCIR is located in E6 panel.
K. Main/APU Battery Charger Detection Enable Relay
(1)
AIRPLANES WITH 30-MINUTE STANDBY POWER; The main/APU battery charger detection enable relay K10424 switches electrical power to the main battery current monitor and the main battery charger detection relay K10425 from the battery bus to the ground handling bus whenever the ground handling bus is energized. This ensures that the battery charging detection circuit is powered whenever the ground service bus, which powers the battery charger, is powered. Relay K10424 is in the P6 panel.
(2)
AIRPLANES WITH EXTENDED STANDBY POWER; The main/APU battery charger detection enable relay K10424 switches electrical power to the main battery current monitor and the main battery charger detection relay K10425 from the battery bus to the ground handling bus whenever the ground handling bus is energized. Relay K10424 performs the same function for the APU battery current monitor and the APU battery charger detection relay K10418 (Ref 24-33-00, Standby Power System). This ensures that the battery charging detection circuit is powered whenever the ground service bus, which powers the battery charger, is powered. Relay K10424 is in the P6 panel.
3. Operation
_________
A. Functional Description
(1) Main Battery System (Fig. 2)
(a)
The main battery and charger are connected to the hot battery bus, and supply bus loads.
(b)
In normal operation, the STBY POWER and BAT switches on M10062 standby power control panel are in AUTO and ON positions, respectively. The DC under voltage sensing relay is energized. This energizes the main battery transfer relay through the de-energized autoland bus isolation relay. The main battery relay is de-energized, grounding the mode control input of the battery charger. The charger is in the charge mode.
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