EnForcer™ SCR Service Manual I.B. 1561
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memory. If AC power is lost during a charge cycle, the charge cycle will resume after a random delay when AC power is
restored. This allows the charger to return to where it left off when power is restored. NOTE: There are no trimming
potentiometers located in this charger.
Caution must be observed when handling or taking measurements on the PC board. The control common, or
ground, is tied to the positive battery buss. This is especially important to consider when taking measurements on the
board while it is operating.
CONTROL CIRCUITRY
The control circuitry measures current via the precision shunt located in the positive lead of the charger. DC Voltage is
measured by means of a precision resistor circuit.
WARNING:
Under no circumstance should the starting current be adjusted to higher than the charger’s
ampere-hour nameplate rating times 0.16, or overheating of the charger will occur.
The control circuitry has three phases of charge cycle. When set for SEALED it has four:
1) Constant-Current control at the start-current setting( .16 times battery AH rating).
2) Constant-Voltage control at the Gassing-Voltage (80%) point setting.
3) Constant current at finish rate.
4) Finish voltage will not exceed 2.53 VPC (SEALED configuration only).
These modes of operation are determined by the recharge characteristics described in the following sections.
The control circuitry is connected to three small windings off the main transformer through connector J1. The value of
these AC voltages can be found in the troubleshooting section of this manual. These windings serve several purposes:
1. Provide the signals that enable the control circuitry to synchronize and determine the proper phase angle to gate
on each SCR.
2. Provide power to the control board. The controller will give an AC fault if any of the three phases becomes low or
distorted, or if any of the three AC fuses clear.
Each SCR is gated with a DC pulse. The red lead of the SCR is tied to control common, and the white gate lead is tied to
the gate-firing circuit on the control circuitry. The control will automatically balance SCR currents to within 10% at the
beginning of each charging cycle.
Refer to later sections of the manual for specific measurements and values that can be expected for normal charger
operation.
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