DC POWER SOURCES
MAIN BATTERIES
Two main electrical system batteries are lo-
cated, one above the other, in the tailcone
(Figure 2-3). The upper battery is connected
to the left generator bus by depressing the left
battery switch and the lower one is connected
to the right generator bus by depressing the
right battery switch. When the battery switches
are selected on, they provide a source of elec-
trical power for engine starting and for emer-
gency operation in the event of dual generator
failure. They also provide power to three hot
busses and two emergency hot busses even
when the batteries are selected off.
The standard batteries are nickel-cadmium
(Ni-Cad) (24 VDC, 27 amp/hour, 30 minute
duration). Optional batteries are lead-acid (24
VDC, 28 amp/hour, 30 minute duration) and
Ni-Cad 24 VDC (38 amp/hour, 60 minute du-
ration). JAA certificated aircraft have the Ni-
C a d ( 2 4 V D C , 3 8 a m p / h o u r, 6 0 m i n u t e
duration) batteries as standard installation.
The main batteries are vented overboard
through two tubes that extend through the tail-
cone skin on the left side just aft of the tail-
cone baggage door. The protruding end of the
tubes are cut at an angle so that one tube takes
air in to vent the batteries and the other ex-
hausts the gases from the battery cases. On air-
craft equipped with the optional APU, the
upper battery vent is located on the left side
of the fuselage, slightly above the aft end of
the left engine pylon connection.
Electrical power from each battery is used to
close the corresponding battery contactor when
the main battery switches are selected ON.
When the battery contactors are closed, the
main batteries are connected to the respec-
tive generator bus (Figure 2-18).
When the airplane is on the ground, the bat-
tery contactors are controlled by voltage sen-
sors to prevent discharge below 14 volts. If a
battery is below 14 volts, the contactor will not
close when the battery switch is selected on.
If the battery voltage falls below 14 volts for
more than 10 seconds while on the ground, the
contactor will open. Battery depletion pro-
tection is inhibited when airborne and during
engine starting on the ground. If the batteries
are above 14 volts, they can be connected and
recharged in the airplane by connecting a GPU,
APU or aircraft generator to the electrical sys-
tem.
The Before Starting Engines checklist in-
cludes turning on the L BATT, R BATT and
EMER BATT switches and checking each bat-
tery voltage. Prior to connecting a GPU or
APU to the electrical system, individual bat-
tery voltages can be read on the SUMRY or
ELEC schematic displays on the EICAS or
MFD display units (Figure 2-10).
Battery temperature monitoring and overtem-
perature warning for Ni-Cad batteries are also
provided via the EICAS/MFD displays and
the crew warning panel (CWP).
In the event of a double generator failure, the
aircraft batteries, in conjunction with the emer-
gency battery, will provide power for the nec-
e s s a r y e s s e n t i a l e q u i p m e n t f o r a l i m i t e d
duration.
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
2-3
FOR TRAINING PURPOSES ONLY
FlightSafety
international
Figure 2-3. Main Batteries Location