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scribed in this art icle will:
• Monitor the state of charge of
station backup batteri es.
• Maintain batteries a t full
charge. preventing overcharging.
• Pro vide a visual and/or aural
a larm that wa rns o f low batte ry
voltage.
• Indicate voltage and c urrent
supplied 10 the transceiver.
The Circuit
Lead·Acld Battery
Col",
Sec Figure I. This proj ect ineludes
a voltage-limited regulated power
supply operated from the AC line and provides
up to 3 ampe res to maintain the batteri
es at full charge. Charging voltage is
constant at the normal full-charge level , so
the charging current drops as full charge is
approached, and full charge is maintained
with a trickle current. This charging voltage
can be adjusted between approximate­
Iy 10 and 15 ¥DC to accommodate leadacid
(l3.8 V) o r lead calci um (I3.2V,
I3.5V maximum) deep-cycle storage batterics.
A separate connection is provided so an
external charger can be used when greater
than 3 am peres is needed to charge a partially
discharged battery. Any standard automobile
battery charger can be used, setting
the charging current at no more than
10 percent of the ampere-hour capacity of
Red
Yellow
Green
Red
Table 1. Battery Condition
Meter Calibration
Voltage
11.6 and below
11.6-12.0
12.0-.13.8
13.8 a nd higher
Lead calcium Battery
Color
Red
Yellow
Green
Red
Voltage
11.6 and below
11.6-12.0
12.0-13.5
13.5 and higher
the battery. Internal circuitry will maintain
the charging voltage to the battery at the
nominal full-charge vo ltage level. regardless
of the voltage supplied by the external
charger, whic h will be 2 vo lts o r more
greater than that applied by the regulator to
the storage battery. WARNING: Do not
fast-charge deep-cycle storage batteries!
A pair of meters calibrated to indicate
20 VDC an d 20 ADC full-scale monitor
voltage a nd c urrent pro vided to the rig
when battery power is used.
A separate, suppressed zero. expandedscale
meter calibrated over th e range o f
about 10 to 15 VDC allows immediate and
constant indication of the state of charge of
the station 's bac kup battery. This meter
scale is calibrated in bands of red, yellow
and green. as e xplained in Table I. The
narrow ye llow segment is based on the as-
s um ption that so li d -state
transceivers may not operate properly
be low +12 VDC. The internal
power supply is used to ca librate
this meter. A DMM should be used
fo r greates t acc urac y. Colored
markers can be used to produce the
multicolored scale.
An alarm circ uit is included to
indicate when the battery has been
discharged by 60 percent to th e
11.6 V D C level. When batte ry
voltage is above 11.6, th e g ree n
LED wi ll be illuminated; when voltage
falls to 11.6, the green LED goes out and
the red LED ligh ts. A piezo audible alarm
sounds at this lo w voltage level unless silenccd
by the toggle switch controlling it.
A pair of fixed three-terminal regulators
are included to provide +9 and +6 VDC
for station accessories with outputs terminated
in RCA jacks. An additional RCA
jack provides regulated voltage from either
the internal AC supply or the storage batte
ry for accessories requiring this voltage.
Most small 12 volt relays have a coil resistancc
of 100·300 ohms and require 50 to
150 rnA for operation. Because this curre nt
must flo w th rough switch transisto r 04.
the power dissipated is much higher than
can be handled by any of the small signal
transistors usually available (2N3904,
etc.). Allhough at first glance it may seem
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P .O . BOX 16646
HAT TIESBURG . MS 39404
C/RCU 104ON READlA SEIMCf: CARD
ME·165 SWR POWER METER