INSTRUCTION / TROUBLESHOOTING MANUAL FOR MODEL A75M
PAGE 6 OF 13
The Model A75M charger accomplishes its charge cycle completely automatically without the use of any moving
parts except for the input AC contactor.
It is recommended that the connector used for the battery/charger connection have an auxiliary control
contact. (A contact that makes last and breaks first.) This contact should be wired to the battery positive on
the battery side of the connector and to Pin #2 of the terminal strip on the charger side of the connector. (The
jumper bar between Pins 1 and 2 must be removed when using the auxiliary control contact.)
An SCR regulator controls the charge rate so that the charger puts out near maximum output current up to the
gassing point of the battery, then automatically reduces the output current down to a trickle charge.
The charger provides automatic AC input line compensation. This eliminates the need for adjusting taps to
match the input line voltage. After the AC voltage taps are set, see INSTALLATION. The automatic
compensation also eliminates charging problems that arise from a varying input line when charging continually
or for two or three shift operations.
The unit is self-protecting when subjected to abnormal overloading conditions.
It should not be necessary to make any adjustments to this charger. Because of the stability of design, the unit
needs no periodic adjustment. This, along with the rugged construction and conservatively rated components,
insures long life and trouble-free operation.
Should any adjustments be necessary, a factory service representative should be contacted.
The automatic start/stop feature senses the connection of the battery and determines if it is in the proper
range, 1.4 volts per cell to 2.5 volts per cell, and then slowly ramps the output current up to start the charge.
If the discharged battery is not the correct number of cells or if the correct battery is over discharged the unit
will not start and the digital display will indicate number "0003". The charger will automatically turn off at the
end of the charge cycle.
An on/off switch is provided to de-energize the charger. Be sure to turn this switch off before disconnecting
the battery during the charge cycle. (After disconnecting the battery, place the on/off switch to the "ON"
position to activate the auto/start function.)
In the normal mode, the charger will charge the battery for 3 hours after the 80% point is reached (unless the
rate program terminates the charge first) or the battery is disconnected. In the equalize mode, a 6 hour timer
is initiated after the 80% point is reached.
A momentary equalize switch is provided so that equalizing may be selected to give a 6 hour charge after the
80% point is reached. Equalizing should be done periodically as recommended by battery manufacturer. This
switch, when activated, will start the equalize charge mode for that cycle only. After completion of the cycle,
the charger will automatically be reset to the "normal" mode.
When the 80% point is reached, the 80% charge lamp will flash at a one second rate. At this point, the timer
in the SCR is set for 3 or 6 hours depending on whether or not the equalize mode is active. The charger will
continue the trickle rate until the SCR control turns unit completely off. When a charging cycle is completed
correctly, the 80%/Complete light will be on solid until the battery is unplugged and the amp hours returned,
elapsed charging time and elapsed time from charge complete will be displayed. Unplugging a charged (charge
complete light "ON") battery will place the unit back in the autostart mode.
Disconnecting the output connector while a battery is being charged is not recommended.
If the
battery is disconnected during a charge cycle, the control will turn off the charger, the complete light will not
light, all timers will reset, and the unit will go into the autostart mode.
If the battery never reaches the 80% charge point (due to battery failure), the unit will turn off in 12 hours
from the override timer. The complete light will not light. The "ON CHARGE" light will turn off, the "FAILURE"
