When the battery pack temperature is more than 10°C
(18°F.) below ambient, thermistor RT (BATT) exhibits a high
resistance, causing the voltage on A13-13 to be larger than the
voltage on A13-14. (The same thing would occur if there were
no battery pack present). There is no output from A13-6 or
A13-10. Transistor Q3 and LED READY indicator DS2 remain
off. The battery pack charges at the trickle charge rate, deter-
mined by series resistance R24, until the temperature is less
than 10°C below ambient. At less than 10°C below ambient,
the voltage at A13-13 is still larger than the voltage on A13-14,
the output at A13-6 goes high causing transistor Q4 to conduct,
turning Q3 on and beginning the high-rate charge.
As the battery pack temperature increases to 10°C above
ambient at end of charge, the voltages at A13-13 and A13-14
become equal, indicating the bridge circuit is balanced and the
battery pack is fully charged. A14-6 goes low, causing Q4 to
stop conducting. Q3 cuts off and the charge rate switches from
the high charge rate to the trickle charge rate . The equal
voltages on A13-13 and A13-14 cause the output at A13-10 to
go high, turning READY indicator DS2 on.
A memory circuit internal to A13 is set so that the same
battery can not be recharged at the high rate unless it first has
been discharged or removed from the charger. When the battery
pack is removed from the charging insert, RT (BATT) is re-
moved from the bridge circuit causing the bridge to again be
unbalanced. A13 senses the bridge in an unbalanced state, the
voltage A13-13 being larger than the voltage on A13-14, and
resets the charger memory. Microswitch S1 (RADIO DE-
TECT) will also remove power from the charger circuits,
causing the memory to reset.
VOLTAGE CONTROLLED CUT-OFF
The voltage controlled cut-off circuit monitors the battery
voltage and cuts off regulator Q3 when the battery charging
terminal voltage exceeds 9.5 Vdc. It is comprised of Compa-
rator A7, Charge Control IC A13, and associated circuitry.
A reference voltage derived from voltage divider R37,
R38, R41, and zener diode CR12 is applied to pin 2 of Com-
parator A7. Resistor R43 is adjusted for a battery charging
terminal voltage of 9.5 Vdc. A voltage equal to the reference
voltage on pin 2 is applied to pin 3 of A7. This causes A7-1 to
go high, applying a lesser voltage to A13-14 than is applied
to A13-13. This causes A13 to turn Q3 off and turn READY
indicator DS2 on. NOTE: During charging there is one
diode drop between the (+) charge terminal and the (+)
terminal of the battery pack.
POWER INPUT CIRCUIT
When a radio is present in the Vehicular Repeater
Charger, 13.8 Vdc from the vehicle battery is supplied to the
Charger board through a 5 ampere fuse and J1-6. This
voltage is then passed through normally open (no) contacts
of S1 and terminated at J7-4 on the Charger board. Diode
CR1 provides reverse voltage polarity protection. The
charger circuit is powered through a noise filter consisting
of C1, C2, L1, and C7.
When the radio is removed from the charging insert,
radio detect microswitch S1 closes and applies 13.8 Vdc to
the base of repeater enable transistor Q2 on the Display
Repeater board. If Q2 collector voltage (from J2-1) is pre-
sent, and if the REPEATER OFF-ON switch is in the ON
position, then the REPEATER ENABLE line (J1-3) goes
high.
DISPLAY REP CA2
The Display board provides the current status informa-
tion for the Vehicular Repeater Charger and radio. It contains
the READY, CHARGE, and REPEATER ON indicators and
associated repeater control circuitry. The cathodes of DS2
and DS3 are at ground and turn on when a positive voltage
from the charge control circuit is applied.
READY indicator DS2 is controlled by A13 and turned
on when the battery is fully charged as indicated by a positive
voltage being applied from A13-10 through J7-7 to the anode
of DS2, turning DS2 on.
CHARGE indicator DS3 is controlled by BATT SET 2
transistor Q2. When the battery is being charged Q2 is turned
on, applying 13.8 Vdc from the battery input at J1-6 through
J7-6 to the anode of DS3, turning DS3 on.
REPEATER ON indicator DS4 is controlled by the
REPEATER OFF-ON switch. A+ from the mobile radio is
applied to the anode of DS4 through J2-1. A+ from the
battery is applied to the base of Q2 through J1-6, S1, and
J7-4. When the REPEATER OFF-ON switch S1 is turned
ON, A- is applied to the emitter of Q2, turning Q2 and DS4
on.
LED BOARD CA1
LED board CA1 contains the RADIO ENGAGED indi-
cator. When the POSILATCH switch is moved to the
latched position, battery voltage is applied to the anode of
DS1 through J1-7 and S3, turning the RADIO ENGAGED
indicator on.
INSTALLATION
Install the Vehicular Charger in a convenient place
where it will not interfere with the safe operation of the
vehicle. Refer to the Installation manual for specific instal-
lation instructions.
MAINTENANCE
The Maintenance section contains Disassembly instruc-
tions, Troubleshooting Procedures, and Adjustment Proce-
dures. A Test Adaptor may be constructed to facilitate
servicing the Vehicular Charger. The Test Adaptor is used to
simulate actual battery pack conditions and to determine if
the charger is working properly. Simulations include cold
battery pack, battery pack at room temperature, and hot
battery pack. Pertinent information is provided in the last
section of this manual.
DISASSEMBLY PROCEDURES
To remove the Top Cover:
•
Remove the six Phillips head screws on the back of
the housing. (Three at the top edge, two at the
bottom corners, and one in the center).
To Remove The Charge Board:
•
Remove the top cover.
•
Remove the four screws from the Charge board and
one screw from the heatsink for Q3.
To Remove The Repeater Display Board:
•
Remove the top cover.
•
Remove the four screws securing the Display board
to the chassis.
Figure 3 - Vehicular Repeater Charger
Figure 4 - Simplified Temperature Cut-Off Circuit
LBI-31869
LBI-31869
3
