Specialty Concepts SC3/20 - Manual (Page 14)

M O N I T O R I N G
The system operation can be monitored by using the digital meter and the lights on the front of the
controller.
DIGITAL DISPLAY: The Digital display on the front of the SC3/20 provides metering of four
parameters, selected by a four position slide switch to the right of the display, labeled A, B, C and
D.
POSITION A - "BATTERY VOLTAGE": This displays the system battery voltage. The battery
voltage is a general indication of battery condition, or capacity. Battery voltage will change
when the battery is being charged and discharged, with the amount of change depending on
the amount of charge current or discharge current. A fully charged battery that is not being
charged or discharged will be at about 12.6-12.8 volts. The normal range of a 12 volt battery is
about 11 to 15 volts. A voltage below 11 volts would indicate a dead battery, and over 15 volts
is definitely an overcharged battery. It is best to keep the batteries above 11.5 and below 14.5
for maximum battery life and performance.
POSITION B - "ARRAY CURRENT": This displays the amount of current the solar panel is
generating. Any current generated by the solar panels will be used first to operate any loads
that are on, and any left over will go into the battery for charging. The array current reading
can be used to optimize the array tilt angle by moving the array (if possible) and noting when
current is maximum. Consult the panel supplier or literature for rated output to see what the
output should be for the total number of panels in the system under ideal conditions. Ideal
conditions would be a bright sunny day, with the panel aimed right at the sun and no shadows
or dirt on the panel.
POSITION C - "CHARGE SET-POINT": This position displays the charge termination voltage
set-point that the controller is currently calibrated for. This display will have a negative sign,
and will read in tenths of a volt. For example the setting of 14.3 will be displayed as -143. This
setting can be used to verify the termination set-point, or for re-calibration. All monitoring or
recalibrating should be performed at times of mild temperature (or “room temperature”). In a
warm or cool condition, the display reading will stray from the actual voltage set-point. For re-
calibration, refer to the “CHARGE SET-POINT ADJUSTMENT” section.
POSITION D - "CURRENT, EXT. SHUNT": This position displays the reading from an external
shunt. This reading could be used for a charger or alternator or for monitoring loads such as a
DC source center or an inverter. Refer to “EXTERNAL SHUNT FOR 2nd CURRENT
READING” section.
“CHARGING” LIGHT: The "CHARGING" light will be on when the array is active (generating
voltage) and the battery needs charging. When the battery is at a low state of charge, the light
will be on continuously during the day. When the battery charges up, the light will go out for a
while (until the voltage drops a little) and then will be on again. When the battery is close to full
charge, the light will be on for short periods of time, and off for longer.
NOTE: The charging light can be on when there is voltage from the solar panel and the battery
can use more charging. This could result in the "CHARGING" light being dimly lit at night when
the panels are under street lights or a full moon.