Samlexsolar SC-05 Owner's Manual - page 7
6 | SAMLEX AMERICA INC.
SAMLEX AMERICA INC. | 7
SECTION 3 |
Principles of
Operation
3.2 FACTORS AFFECTING VOLTAGE AND CURRENT OUTPUT OF A SOLAR PANEL
The following factors affect the voltage and current of a solar panel:
•
The output voltage is not affected very much by the light conditions - under shaded / cloudy
condition, the output voltage will not vary very much as compared to bright sunshine
•
The output current is very sensitive to the intensity of light and will drop considerably
under shaded or cloudy conditions
•
Variation in temperature has a sizable effect on the output voltage – a Negative
Temperature Coefficient of -2.3 mV / °C / Cell resulting in increase in the voltage at lower
temperature and decrease in the voltage at higher temperature
•
Variation in temperature has negligible effect on the current output
•
The output current can increase by 25 % due to what is known as the “Edge of the Cloud
Effect”. As the sun moves between a hole in the clouds, the solar panel will see the full
direct sunlight combined with the reflected sunlight from the clouds
3.3 BATTERY CHARGING OPERATION USING A SOLAR PANEL (See Fig 1).
When a battery is directly connected to the solar panel, the voltage of the loaded panel will be
equal to the initial battery voltage. At this point, the charging current (I) will be equal to the
corresponding value of the initial battery voltage on the V-I Curve
The current (I) fed from the panel will start charging the battery and the battery voltage will
start rising. As the battery is always connected to the panel, the panel voltage will be the same
as the battery voltage. It will be seen from the V-I curve that as the battery voltage rises, the
charging current will start reducing.
When a battery is fully charged, it will not require any further current for charging except the
very low self discharge current. If a charging current higher than the self discharge current
is continued to be fed to a fully charged battery, it will lead to damage to the battery due to
overcharging resulting in overheating and loss of water due to excessive electrolysis (conversion
of water to oxygen and hydrogen).
3.4 CHARGING A BATTERY BY A SOLAR PANEL USING A CHARGE CONTROLLER
For full scale charging of a battery from a solar panel, the output of the solar panel is required
to be fed to the battery through a Charge Controller. The Charge Controller transforms the
input power from the solar panel to regulated voltage and current necessary to safely charge
the battery as per the required charging algorithm e.g. 2/3/4 Stage Charging Algorithm.