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Section I11
Paragraphs 3-16 to 3-27
Model 204B
3
-
16,
RECHARGING NICKEL- CADMIUM
BATTERIES.
3-17. The batteries should be considered as fully
discharged when maximum oscillator output drops
below 5.0 volts r m s opencircuit o r l e s s than 2. 5 volts
r m s into 600 ohms. The batteries
w i l l
not
operate
much longer when this point is reached and the osci-
llator probably will not meet specifications. Exces-
sive discharge of batteries may damage them
o r
shorten their life.
3-18. To recharge batteries, turn oscillator O F F and
connect power cord to a suitable power source. The
batteries will be fully charged in approximately 60
hours a t a 5 . 5 miliiampere charge current and 30
hours a t
a
11 milliampere charge current
if
they were
fully discharged
at the beginning. The instrument can
be turned on for use after an initial charge of
at least
20 minutes. If the batteries were only partiallydis-
charged, the oscillator can be turned on for use
at any
time. The charge rate is the same whether the osci-
llator is O F F
o r operating; therefore, very little in-
crease in charging time will be required
i f
the instru-
ment is used while the batteries a r e being recharged
The charge circuit can be increased with the charge
current adjustment R102 ( r e f e r to figure 5-11) to
a
maximum of 11 milliamperes to provide
a
quick
charge. The 11 milliampere charge rate should be
used for quick charge only. Repeated chargingat a
high rate
w i l l
shorten battery life.
3-19. The batterJes can beocharged
at
ang tempera-
ture between +32 F to +122 F (0 C to +50 C). How-
ever, to obtain optimum battery life,
recharging
should be tone at
a
temperature of 80.6'F
*lO°F
(27OC *5.6 C).
CAUTION
THE FOUR NICKEL-CADMIUM
BATTERIES
ARE HERMETICALLY SEALED AND CAN BE
DAMAGED I F CHARGED AT A FAST RATE
AT
A
TEMPERATURE EXCEEDING 1 2 2 F
(5OOC). I F THE CHARGE CURRENT ADJUST-
MENT
HAS
BEEN SET FORA QUICK CHARGE
RATE, PLACE THE INSTRUMENT I N
A
LOCATION WHERE
THE
AMBIEYT
TEMPERATURE DOES NOT EXCEED 104 F
(4OOC).
3-20.
CYCLE-LIFE O F NICKEL-CADMIUM
BATTERIES,
3-21.
As extremes in temperatures a r e approached,
the cycle-life (complete charge-discharge cycles) of
the batteries is reduced. Storage a t high tempera-
tures w i l l increase the self-discharge rate and also
decrease the cycle-life.
Permanent battery damage
may result
if
the batteries a r e stored
at a high tem-
perature for a prolonged period.
3-22.
Battery cycle-life canbe extended by recharg-
ing before the batteries a r e completely discharged,
charging and discharging at
a
rate which is slower
than the maximum ten-hour rate specified by the
manufacturer, and by not overcharging.
3-23.
The cycle-life of the batteries i s based, by
the manufacturerer,on an endpoint of 80% of the rated
225 milliampere-hour capacity. This is with
a
ten-
hour charge and discharge current of 22. 5 milliam-
p e r e s with discharge c a r r i e d to the normal ten-hour
end voltage (1.10 volts/cell x 5
=
5.50 volts/battery)
on every cycle. Under these conditions a cycle-life
in excess of 100 cycles can be expected.
3-24. When used topowerthe @ Model 204BOscilla-
tor, the batteries a r e discharged a t approximately a
40 hour rate. The batteries a r e not fully discharged
if
they are recharged as recommended in paragraph
3-25.
Optimum battery life can be obtained by fol-
lowing a simple routine of 1) preventing complete
battery discharge by recharging before the oscillator
output level drops below 5.0 V r m s into an open cir-
cuit
(2.
5 V r m s into 600 ohms), 2) keeping the use of
a quick charge to a minimum, 3) operati.i,r a t mod-
erate temperatures whenever possible and 4) by dis-
connecting power cord after 60 hours of continuous
charging with oscillator turned O F F (30 hours
if
charging batteries a t a quick charge rate).
3 - 2 6 .
M E R C U R Y B A T T E R Y R E P L A C E M E N T .
3-27. Battery replacement is required wnen the
oscillator output becomes l e s s than 5.0 volts r m s open
circuit o r l e s s than 2. 5volts r m s into 600 ohms pro-
vided the DC BAL is adjusted correctly. Replace the
batteries with four
6. 75-volt
mercury batteries
(Mallory type TR235R o r equivalent). Refer to figure
3-2, and proceed as follows:
a. Remove top cover retaining screw and slide
cover from instrument.
b. Remove wing nuts and battery clamps.
c. Remove and dispose of batteries according to
paragraph 1-6.
d. Install replacement batteries s o that battery
polarity matches polarity designation on battery
clamps.
e.
f .
Replace top cover.
3-16.
Replace battery clamps and wing nuts.
POLARITY
DES IGN-ATION
WING
N
U T
2 0 4 6 - S - I
I
BATTERY
CLAMP
Figure 3-2.
Rear View of Model 204B Showing
Mercury Batteries Installed.
3-2
01369-2
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