How to measure the current of a solar panel
This article contains explanations on how to measure the current of a solar panel, so we can determine if it is working properly.In order to measure current in the solar panel, it must be exposed to the sun.
How to measure the current of a solar panel
We can make two measurements Imp and Isc . And we have to take into account that the current value that we measure will depend on the actual test conditions and that it will be lower than the value specified by the manufacturer carried out under standard measurement conditions (STC).
A) Measure the current of a solar panel with an ammeter CLAMP :
IMPORTANT: Place the selector in the direct current position (Adc) or in the symbol that we see in image 1.
Measure Current Isc (Short Circuit Current):
1.- Connect the cable + with the cable – of the solar panel. In this way we pass the maximum current that can circulate through the solar panel. There is no danger since the physical limitations of the solar panel prevent the Isc value from being exceeded.
2.- Surround the cable with the ammeter clamp . If the reading is negative, it means that the current flow is in the opposite direction, but what interests us is not the direction of the current, not its value. If you rotate the caliper you will get the positive reading.
Measure Imp Current (Current at maximum power):
1.- Connect the solar panel to the regulator as in normal operation.
2.- Surround the ammeter clamp to any of the cables that come from the solar panel, either the + cable or the – cable. If the reading is negative, it means that the current flow is in the opposite direction, but what interests us is not the direction of the current, but its value. If you rotate the clamp or change the cable you will get the positive reading.
B) Measure the current of a solar panel with a TESTER or digital multimeter :
As these devices do not have an ammeter clamp, we must carry out a series measurement. That is, the current from the solar panel must pass through the tester.
To do this, it is necessary to interpose the tester cables in the path of the cable + or cable – of the circuit.
IMPORTANT:
1.- Change the red cable of the tester from the hole with the sign V to the hole with the sign «A» or «10A». (Look at the maximum value of your tester. In the image 10A. We will not be able to exceed this current). Testers without 3 holes may not be able to perform DC current measurements.
2.- The black cable of the tester must be in the COM hole.
3.- Select the direct current selector (Adc) or the symbol that we see in image 1. If our multimeter does not have the Adc or DCA symbol or the one in figure 1, we cannot measure direct current.
Measure Current Isc (Short Circuit Current):
4.- Touch the red cable of the tester to the + cable of the solar panel. (See image 3)
5.- Touch the black cable of the tester to the cable of the solar panel.
IMPORTANT: Normally the testers or digital multimeters have a current limitation of 10A. So we can only measure solar panels with currents less than 10A and one by one.
Measure Imp Current (Current at maximum power):
4.- Disconnect the + cable that goes from the solar panel to the regulator. (See image 4)
5.- Touch the red cable of the tester to the cable+ of the solar panel
6.- Touch the black cable of the tester to the input of the regulator where the + cable of the solar panel was.
IMPORTANT: Normally the testers or digital multimeters have a current limitation of 10A. So we can only measure solar panels with currents less than 10A and one by one.
What is the Isc of a solar panel? How is the Isc measured?
This value varies depending on the cell and the light irradiation . If when measuring this value it does not coincide with that indicated in the panel specifications, it is slightly lower, there is no need to worry, because a simple fog can affect this value.
When you want to start up a photovoltaic installation , you have to know this short-circuit current Isc , as well as other parameters such as the open circuit voltage (Voc), maximum power (PM), panel efficiency , etc…
To measure the Isc of a photovoltaic solar panel, a digital multimeter (DMM) can be used that uses cables to measure the current, or a clamp meter , more recommended, that uses clamps that close around the cables and measure their current. It is not recommended to measure the short-circuit current of several panels connected to each other, the measurement must be made in individual panels.
To make reliable measurements, the measurement must be made on panels with good sun exposure , these values will be closer to those specified by the manufacturer. In the same way, it is also recommended to connect the module with it in the shade, or covered , in this way sparks that can damage the connectors are avoided, and later uncover it.
When using a multimeter, make sure you make the correct connections. Of course, if the panels are already connected, it is easier and less dangerous to use the clamps.
