Samlexsolar SC-05 Owner's Manual - page 6
6 | SAMLEX AMERICA INC.
SECTION 3 |
Principles of
Operation
3.1 ELECTRICAL OPERATING PARAMETERS OF A SOLAR PANEL
A solar panel can be considered as a current limited source of electrical power with a voltage
versus current relationship as shown in Fig 1.
Voltage - Current Characteristics
Voltage (V), Volts
Cu
rr
en
t (
I), A
m
p
s
0.0
0.2
0.4
0.6
0.8
1.0
0
5
10
15
V
MP
= 16 V
V
OC
= 20.2 V
V
OC
= 21.5 V
V
MP
= 17 V
I
SC
= 0.6 A
I
SC
= 0.33 A
20
25
SC-05
SC-10
Fig 1 Voltage versus Current characteristics
When exposed to the sun and without any load connected, the solar panels will generate an
Open Circuit Voltage (Voc). As soon as a load is connected to the panel, the voltage at the load
will drop and the value of the voltage at the load will be determined by the current (I) drawn by
the load. Please note that at the Open Circuit Voltage Voc, the output current (I) is zero.
The electrical power (P) in Watts fed to the load = Voltage (V) X Current (I).
If the output of the panel is short circuited, the output current will be limited to the maximum
current that the panel can provide. This Short Circuit Current is designated as Isc.
The maximum power Pmp is fed to the load when the operating point is near the knee of the
curve as shown. At this operating point for maximum power output, the voltage is designated
as Vmp and the current is designated as Imp.
Please note that for the portion of the curve between Voc to Vmp, the current drops at a faster
rate. After that, the current is almost constant and equal to the Short Circuit Current Isc.