How to Test Solar Panels?

In this regard, a few crucial components of your solar PV systems depend on regular, adequate electrical testing and inspection. You must be checking your solar panel and the system for effective grounding, environmental degradation and physical damages, surface contaminations, ground faults and damages to wiring.

Testing before installation

If you are going to purchase a solar panel, the solar panels are tested at the manufacturing unit to check these things:

  • Voc – Open circuit voltage
  • Isc – Short circuit current
  • Vmax – Maximum Voltage
  • Imax – Maximum Current
  • Pmax – Maximum power at Standard Test Conditions or Peak Power Output

The testing of solar panels is pretty much simple, you have to multiply voltages and amperage to calculate the precise total wattage.

Read our detailed and pictured guide for testing solar panel wattage here.

Before You Start

  • Cover the front of the solar panel when handling other than collecting measurements since photovoltaic panels generate electricity when exposed to light.
  • Solar panels should only be short-circuited for testing purposes, and only for no longer than five minutes.
  • Verify the system wiring is correct and intact. Refer to the manual for panel information.
  • On the specs label on the back of your solar panel, find the voltage and current ratings. These numbers will be compared with our readings later.
Figure 1 : 370W Solar Panel Monocrystalline Silicon Photovoltaic Module Charging Power solar panel specs label
  • Make sure you know how to use the multimeter. Learning the multimeter anatomy is just a few-minute thing!
  • Confirm that the lighting conditions are appropriate for your system in order to provide readings. You will need full, bright sunshine falling directly onto the panel in order to get the rated output of your panel.
  • Make sure the battery is not fully charged if you’re testing a charge controller because else it won’t be able to receive current.
Figure 2 : A multimeter

Measure Open Circuit Voltage (Voc)

Figure 3: Multimeter and the Solar Panel Connection to measure the Open Circuit Voltage
  1. Your multimeter should be in the DC configuration to do this. So, you can plug the black probe into the COM port and the red probe into the voltage terminal. Now you have to be sure whether you have your multimeter in the DC voltage settings and the correct voltage range.
  1. Bring your solar panel outside, with the monocrystalline side facing up the sun. Tilt it toward the sun for best results.

This will produce a test voltage for you to measure.

Make sure it is a sunny day, the panel is not placed in a shade and the panel is cleaned.

Figure 4: A tilted solar panel
  1. Find the positive and negative cables for your solar panel.

Modern PV panels use a standard connector called MC4. These are a 4th generation connector that allows easy interconnects between PV panels.

  1. Hold your multimeter’s red probe against the metal pin inside the positive connector. Connect the black probe to the negative connector’s metal pin.
  1. Compare the voltage you receive on your multimeter to the open circuit voltage (Voc) indicated in the panel specifications.

If the two values are pretty much close, you have got your panel good.

Measure Short Circuit Current (Isc)

Figure 5: Configuration to measure Short Circuit Current
  1. In this test, you are going to measure the amperage. So, connect the red probe to the amperage terminal and make sure that the multimeter is in the correct range.
  1. Then keep the solar panel in the direct sunlight.
  1. Put your multimeter’s red probe against the metal pin inside the positive connector. Connect the black probe to the negative connector’s metal pin.
  1. Compare the current displayed on your multimeter to the short circuit current (Isc) in panel specifications.

The two values being close enough means that the panel is working well.

Having a spark when connecting the terminals is quite normal….

Measure Operating Current (IL)

Figure 6: Configuration to measure the Operating Current
  1. You have to Connect the panel to the regulator (solar charge controller) and battery.
  1. Ensure that the multimeter is set at 10A, at least to start with. You can change the setting later if required.
  1. Disconnect the positive cable between the battery and the regulator
  1. Measure the operating current by connecting the positive terminal from the multimeter to the positive cable from the regulator, and the negative terminal from the meter to the positive battery terminal

If you want to know how close your solar panel is to its maximum, you can compare this value to the current at maximum power (Imp) on panel specifications.

A fully charged battery might not be able to accept current, giving a low reading

If you connect the meter reversed, you will get a negative current showing.

Test the Regulator

Figure 7: Configuration to test the regulator
  1. Measure the operating current
  2. Reconnect the battery and solar panel without using the regulator.
  3. Disconnect the positive cable between the battery and the panel.
  4. Connect the positive and negative leads of the multimeter to the positive cable coming from the panel and the positive battery terminal, respectively, to determine the operational current.
  5. If an operating current is now available without the regulator but there was none when the regulator was installed, the regulator may be defective.

More tests

Continuity Test

To ensure maximum protection for your solar power system it’s good to conduct the Continuity test. Continuity is the presence of a complete path for current flow. This test can be accomplished using the Continuity Test feature of a digital multimeter.

You have to set your multimeter in the resistance setting. When placing the 2 probes between 2 ends of a circuit, if the circuit is open, OL (Open Loop) will be displayed.  If the circuit is closed there will be a resistance measurement which depends on the rated resistance of the component.

Insulation Resistance Test

Insulation resistance tests are performed to confirm and demonstrate that electrical wiring systems and equipment are reliable.

Never conduct insulation tests on batteries or other energy storage systems

REMEMBER: This test is performed with the circuit de-energized.

You can use an IR tester or megohmmeter to test insulation resistance. The two probes of the IR tester are placed at two components which we have to test the insulation and a current is passed through them. The megohmmeter indicates the insulation resistance value and gives a result in kW, MW, or GW. If the IR tester reading is high then you have good insulation. On the other hand, the insulation is inadequate if it is low.

PV systems may also undergo special testing as part of maintenance or to address a particular issue. Specialized equipment and sometimes the supervision of professionals are needed for these tests.

TestReason to Conduct
Power Quality AnalysisTo monitor grid conditions: voltage sags and surges, power factor and phase angles, harmonics over time

To measure ac ripple currents on dc circuits
Polarity TestingBecause the polarity of every source circuit and the entire PV power source must be verified prior to connecting to any dc utilization equipment.
Thermal ImagingTo identify hot spots or overheating equipment
Inverter Efficiency TestsTo determine power for reactive circuits and components
Shading AnalysisTo evaluate and quantifies the impacts of shading on PV arrays

Visual inspection

When you look well into your solar panel well you might see several flaws.  Those visual defects are

  • broken, cracked, or torn external surfaces, including superstrates, and substrates
  • bent or misaligned external surfaces
  • crack or voids in a cell
  • bubbles or delamination forming
Figure 8: Snail Trialing a Solar Panel

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