Alternate Operation
Single Battery
Option
The alternate power source for standby power is the battery. With the standby power switch
in the AUTO position, the loss of all engine or APU electrical power causes the battery to
power the standby loads, both in the air and on the ground.
The AC standby bus is powered from the battery via the static inverter. The DC standby
bus, battery bus, hot battery bus, and switched hot battery bus are powered directly from
the battery.
The standby power switch provides for automatic or manual control of power to the standby
buses. In the AUTO position, automatic switching from normal to alternate power occurs if
power from either AC transfer bus 1 or DC bus 1 is lost. Positioning the switch to BAT
overrides automatic switching and places the AC standby bus, DC standby bus, and battery
bus on battery power. The battery switch may be ON or OFF. If the battery switch is OFF,
the switched hot battery bus is not powered.
Positioning the standby power switch to OFF de–energizes both the AC standby bus and
the DC standby bus and illuminates the STANDBY PWR OFF light.
