Lamarche A70B Instruction Manual - page 7
INSTRUCTION / TROUBLESHOOTING MANUAL FOR MODEL A70B
PAGE 7 OF 16
NOTE: CODE 100 INDICATES DEFECTIVE S2A-122A. PRINTED CIRCUIT BOARD OR S2A-123 OR
WRONG AC VOLTAGE FROM THE CONTROL TRANSFORMER.
The Model A70B charger accomplishes its charge cycle completely automatically without the use of any moving
parts except for the input AC contactor.
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 on a taper
curve as the battery comes up to full charge. The shape of this tapering curve is produced by the software in
the microprocessor. The voltage of the battery is continuously sensed by the microprocessor which calculates
the changes in control that are necessary to properly charge the battery. These new updates are sent to the
unit's SCR's at a rate of approximately 100 times per second.
The charger provides automatic AC input line compensation. This eliminates the need for adjusting taps to
match the input line voltage. 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. The current limiting feature
limits the output current to not more than 105% of the output rating of the charger.
It should not be necessary to make any adjustments to this charger. Should any adjustments be necessary, a
factory service representative should be contacted.
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.
The automatic start/stop circuitry senses when a battery is connected and then slowly ramps the output current
up to start the charge. If the discharged battery is not the correct number of cells, the unit will not start and
the digital display will indicate number "0003".
The automatic start/stop feature senses the connection of a battery and determines if it is in the proper range,
1.6 volts per cell to 2.45 volts per cell. It also determines if AC input line voltage is in the proper range. The
high AC input voltage limit is 10%, the low AC input voltage limit is -15% of nominal. Five seconds after both
of these conditions have been met, the AC input contactor will close. If the recommended procedure is not
followed and the DC output connector is disconnected from the battery, the AC input contactor will open within
five seconds.
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.
With the normal/equalize switch in the normal mode, the rate of change program begins after the charger is
energized. The rate program operates by measuring the battery current continuously during the charge cycle
and storing it. As new battery, current information is received, the difference between the old and new values
is calculated to determine the rate of change during the interval. This rate is then compared against a
reference and the decision is made whether or not to terminate the charge cycle.