Specialty Concepts SC3/20 - Manual (Page 12)

O P E R A T I O N
The charge regulation aspects of the SC3/20 are completely automatic. No user interface is
required after installation. This controller will regulate the charging of batteries during conditions
of heavy usage, or when left unattended for long periods of time.
SWITCHING SHUNT, PULSE CHARGE REGULATION: When in the charge mode, the SC3/20
allows maximum available array current to flow into the battery through a blocking diode,
lighting the yellow "CHARGING" light. As the battery charges, the voltage will rise slowly until
it reaches the charge-cutoff set-point. At this point, the "CHARGING" light goes out, the green
“CHARGED” light goes on and battery charging stops. When charging stops the battery
voltage will fall, and when the battery voltage drops to the charge resumption set-point, the
SC3/20 will resume charging.
A TYPICAL DAY: A typical daily cycle will be as follows. As the charging starts for the day and
battery capacity is low, charging will be continuous and the “CHARGING” light will be on all the
time. As the battery charges up, current will pass into the battery for awhile and eventually
stop. Later, charging will resume and the system will continue this cycle throughout the day.
During the course of the day, the duration of the charging period of each cycle will get shorter
(cycling on for shorter periods and staying off longer). When the battery is close to full charge,
it will pulse current into the battery to achieve and maintain full charge. This pulse charging is
indicated by the "CHARGING" light occasionally turning on and off, and the ‘CHARGED” light
turning off and on.
B A T T E R Y F U S E
“BATTERY FUSE” - A battery fuse is included for the SC3/20. This will protect the controller from
over-current from the solar panels, reverse polarity from the batteries and a short circuit in the
system. Fuse type: 20 AMP AGC.