COMPONENT MAINTENANCE MANUAL
BA27
24-01-01
T
h
is docum
ent
contains D
a
ta
control
led by th
e U.S. Export Admini
str
a
tion
Reg
u
lati
ons. Di
versio
n or use
contrary to U.S. law is
proh
ibit
ed
2.
U
Operation
A General
The battery is charged (and also sustained) on the aircraft by a modified
constant potential mode via a series 0.75 ohm resistance and relay contacts
from the flight controls dc bus within the Flights Controls Power Supply
Assembly. Whenever the aircraft engines are in operation, the relay contacts
are closed and the flight controls dc bus is powered from two regulated
converters supplying a regulated 28.2 V dc. When the aircraft engines are not
in operation (ground operation), the battery is connected to the flight controls
bus via the 0.75 ohm resistance and relay contacts only when the voltage on
the flight controls bus is within the range of 26.5 V dc and 30.0 V dc. Under
operation with ground service power, the flight controls dc bus voltage is
normally between 27.0 and 27.5 V dc. The operation of the relay contacts that
connect the battery (via the resistance) to the flight controls dc bus is controlled
by logic circuitry within the Flight Controls Power Supply Assembly.
The battery is capable of supporting short duration fill-in and path check loads
of approximately 15 A dc as well as a parasitic demand of 1.5 mA dc (when the
airplane is without electrical power) and an emergency condition loading of up
to 30 A dc for up to one minute duration. The worse case daily usage (with
twelve flights per day) and with no emergency is approximately 0.25 Ah.
U
CAUTION
U
:
The battery is maintenance free. Under no circumstances
should any attempt be made to introduce any substances, e.g.,
acid, distilled water or alkali, to the battery.
B Temperature
Effect
The ideal environmental temperature for battery operation is 23°C (73°F) to
25°C (77°F). Long-term exposure to temperatures above 30
C (86°F) can
shorten the life of the battery.
As the temperature falls, the available capacity of the battery is reduced, which
causes a reduction in performance. However, this is not a permanent condition
and the capacity will be restored as the temperature rises. Long-term exposure
to low temperatures will not damage the battery.
Page 3
June 09/06