In this article you’ll learn how to test a solar panel.
What you’ll find below is a step-by-step guide on how to check if a solar panel is working correctly.
The fact is any solar panels can go wrong or stop running efficiently, but there are specific steps you need to take to make sure your equipment is running efficiently and not lacking power.
If you follow the process outlined below for testing solar panels the right way, you’ll quickly spot any issues that need to be addressed.
In addition, it will give you accurate performance ratings of your equipment so you can calculate what you’re able to power.
Why Test a Solar Panel?
You might want to test a solar panel to make sure it is running correctly or to take accurate power reading based on certain conditions.
When it comes to off-grid systems installed in RVs, cabins, sheds, campervans, and elsewhere, many people attempt to install the equipment themselves, without the help of a professional. If you do this you’ll want to check the equipment is working properly.
In addition, solar panels are built to last a long time, often 25 years or more. Most of the time they need very little maintenance but of course things can go wrong over time. If you feel like there is a fault with your equipment then testing it will identify if anything is wrong.
Finally, the performance and power of solar panels are not consistent. For example, weather conditions can affect the output wattage. In order to make accurate calculations of how much electricity you will generate you will need to run a test. This way you can get reliable data on your system in any given scenario such as direct sunlight or cloud cover.
How to Test a Solar Panel
Testing a solar panel is quite simple with the correct equipment and knowledge.
To complete your checks you will need a multimeter. You will use it to measure the open circuit voltage and amperage (current). Plus you can compare this information to the datasheet to know if you have any specific problems.
Measure Voltage (Open Circuit)
The first thing we are going to check is the Voltage. For these tests, I am going to use the numbers based on my 145W Zamp Solar panel. Of course, you’ll need to find and compare your readings to the datasheet on your own equipment.
- Find Open Circuit Voltage Voc (V) rating of your equipment. This should be included in the specification sticker found on the back. For example, mine is 21.8.
- Switch your multimeter to DC volts.
- Place your solar panel in direct sunlight. (Or shade if you want to test shaded performance)
- Identify the positive and negative cables. Positive will be marked with red and negative with black. Often this just is a small red band on the positive MC4 connection.
- Connect the red multimeter probe to the red MC4 connection. And connect the black multimeter probe to the negative MC4 connection. Ensure the probe and metal pins touch on both to create a circuit.
- The voltage should now show on the multimeter. You can compare this real number to the Voc you noted earlier. It should be close to this value but will likely be a tiny bit less.
Measure Current / Amperage
- Find the Short Circuit Current Isc (A) rating of your equipment. This should be included in the specification sticker found on the back. For example, mine is 8.7.
- Switch your multimeter to DC Amps.
- You must also check your multimeter has a larger fuse size than the solar panel Isc rating. On average multimeters are 10A which is lower than my panels 8.7A.
- Place your solar panel in direct sunlight. (Or shade if you want to test shaded performance)
- Identify the positive and negative cables. Positive will be marked with red and negative with black. Often this just is a small red band on the positive MC4 connection.
- Connect the red multimeter probe to the red MC4 connection. And connect the black multimeter probe to the negative MC4 connection. Ensure the probe and metal pins touch on both to create a circuit. It might spark when you complete the circuit, this is normal.
- The current should now show on the multimeter. You can compare this real number to the Isc (A) you noted earlier. It should be close to this value but will likely be a tiny bit less.
Now you have checked the voltage and amperage you will know if this is an issue with your solar panel performance. When in direct sunlight the readings you take should be close to the information on your attached specifications. If there is a big discrepancy you have a problem.
What are the Common Problems of a Solar Panel?
If your solar panel test did not give you satisfactory readings then you need to identify the loss in performance. Here’s a list of common issues to check:
- Dirt – Start by giving it a good clean. Make sure there is no dirt, dust, bird droppings etc on the face. Anything stopping light from hitting your solar cells can seriously impact performance.
- Shade – Ensure there is no shade or shadow over your solar panel. Even a small bit of shade will mean the current drops across all the cells to match the lowest performer. If you have issues with shade then consider adding optimizers or microinverters.
- Microcracks – All solar panels will degrade slowly over time generally you should see no more than 1% drop in performance each year. Microcracks are invisible to the human eye and will reduce performance while speeding up degradation. Short Circuit Current drop can be a sign of microcracks. Plus, over time you might start to see snail trails or browning where moisture enters the microcracks. Checking for microcracks involves electroluminescence crack detection (ELCD) by a professional.
- Hotspots – Modern solar panels should be protected from hotspots by bypass diodes. Hotspots occur when parts of a panel get too warm and overload, usually during partial shading. It can still happen when there are badly soldered connections in low resistance areas.
- Electrical issues – Faulty or incorrect wiring will impact your panel performance. It is common to see on DIY installations or vehicles that move around a lot. Loose connections and corrosion will hinder the flow of electricity. Make sure all connections are snug, secure, and clean.
- Other Components – If you’ve checked your solar panel and everything seems to work correctly but you’re still not getting enough energy then it could be other components. Check your charge controller is charging your battery properly. Often deep-cycle batteries need replacing. Plus you should test your power inverter for faults.
FAQ on Testing Solar Panels
Still got questions? Let’s answer the other queries running around your head.
To find out if a solar panel is working you can use a multimeter to check the voltage and amperage. This should tell you if current is able to flow at the correct force. Plus you should see ample current and power from your controller and solar inverter.
It is hard to completely test solar panel without the sun. You will still be able to see a voltage and current in the shade but it will be much smaller. At night, it won’t be possible to test a solar panel.
Yes, there are many apps to keep an eye on your solar array. Some manufacturers built wireless monitoring into their systems. You can check out Renogy BT, SolarEdge, Enlighten, Fronius, and SMA Sunny.
You should see a reading on the screen of the solar charge controller that shows you the voltage and amperage of your system. In addition, you can add a battery monitor screen to check charge level. Many power inverters will also show you the battery charge level. Low voltage is a sign of low battery, the voltage should increase as it charges.
Yes, a solar panel has positive and negative wires as it needs to create an electric circuit. Usually, you can find the positive as there is a red marking on the MC4 connector. In addition, look from signals like + (positive) and – (negative). Colors also denote this information red = positive, black = negative.
Common reasons for a solar panel to stop work include no sunlight at night or covered solar cells, faulty wiring, incomplete circuit, excessive damage, other faulty components like charge controller or power inverter.
How to Test Solar Panels Summary
I hope this article has helped you learn how to test a solar panel.
As you discovered, the process for testing solar panels to make sure they are working correctly involves measuring the voltage and current. By knowing it is working correctly you can ensure you have enough energy flowing to your battery and inverter to keep your appliances powered up.
