Solar panel testing (3 methods)
Content
By the end of this article, you will know three different solar panel test methods and be able to choose the one that works best for you.
You need to know how to test your solar panels to ensure you are getting the proper power from them to avoid potential stray drains and connection issues. While working as a handyman and contractor, I did several installations where the residents' panels were installed incorrectly and half of their panels were only running at part power; it's devastating given the cost of installation, another reason why it's important to test them to make sure you get your money's worth.
In general, follow these three solar panel testing methods.
- Use a digital multimeter to test the solar panel.
- Test the solar panel with a solar charge controller.
- Use a wattmeter to measure solar panel power.
Get more details from my article below.
Before we begin
Before proceeding with the practical guide, you should know a few things. First, you need to know why solar panel testing is so important. Then I will give you a brief introduction to the three methods that you will learn about.
When you test a solar panel, you can get a good idea of the power generation and efficiency of that panel. For example, a 100W solar panel should provide 100W under ideal conditions. But what are the ideal conditions?
Well, let's find out.
Ideal condition for your solar panel
The following conditions must be ideal for the solar panel to produce maximum power.
- Peak hours of sunshine per day
- Shading level
- Outside temperature
- Solar panel direction
- Geographic location of the panel
- Weather
If the above factors are ideal for a solar panel, it will operate at maximum power.
Why is my solar panel not working at full capacity?
Let's say your new 300W solar panel only produces 150W. You may be disappointed in this situation. But don't worry. This is a problem that most people face when using a solar panel, and there are two reasons for this.
- The solar panel is not in ideal conditions.
- The panel may malfunction due to a mechanical error.
Whatever the cause, the only way to confirm the problem is to do some testing. That's why in this guide, I'll cover three methods that can help you test solar panels. Whether the panel is working properly or not, you should check it from time to time. This will give you a clear idea of the output of the solar panel.
There are a few things you need to know about these three tests.
When testing a solar panel, you must test the output of the panel.
This means the power of the panel. Therefore, you must measure the voltage and current of the solar panel. Sometimes this voltage and current is more than enough to test the solar panel. In some cases, you may need to calculate the power in watts. You will know more about this when the calculations are shown later in the article.
Method 1 - Checking the solar panel with a digital multimeter
In this method. I will be using a digital multimeter to measure open circuit voltage and short circuit current.
Step 1 - Learn VOC and ISC
First of all, inspect the solar panel and find the VOC and ISC rating. For this demo, I am using a 100W solar panel with the following ratings.
In most cases, these values should be indicated on the solar panel or you can find them in the instruction manual. Or get the model number and find it online.
Step 2 - Set your multimeter to voltage mode
Then take your multimeter and set it to voltage mode. To set the voltage mode in the multimeter:
- First connect the blackjack to the COM port.
- Then connect the red connector to the voltage port.
- Finally, turn the dial to DC voltage and turn on the multimeter.
Step 3 - Measure the voltage
Then locate the negative and positive cables of the solar panel. Connect the black test lead to the negative cable and the red test lead to the positive cable. Then check the reading.
Quick-Tip: When the connection is complete, the multimeter leads may spark slightly. This is completely normal and nothing to worry about.
As you can see, I got 21V as open circuit voltage, and the nominal value is 21.6V. So, it's safe to say that the output voltage of the solar panel is working correctly.
Step 4 - Set the Multimeter to the Amplifier Settings
Now take your multimeter and set it to the amplifier settings. Turn the dial 10 amps. Also, move the red connector to the amplifier port.
Step 5 - Measure the Current
Then connect two multimeter probes to the positive and negative cables of the solar panel. Check reading.
As you can see here, I get a reading of 5.09A. Although this value is not close to the short circuit current rating of 6.46V, this is a good result.
Solar panels produce only 70-80% of their rated power output. These panels achieve maximum performance only under ideal conditions. So, try to read in good sunlight. For example, my second test under ideal conditions gave me a reading of 6.01 A.
Method 2. Checking the solar panel using a solar charge controller.
For this method, you will need a solar charge controller. If you are not familiar with this device, here is a simple explanation.
The main purpose of a solar charge controller is to prevent the battery from overcharging. For example, when connecting a solar panel to a battery, it should be connected through a solar battery charge controller. It regulates current and voltage.
You can use the same principle to measure the voltage and current of a solar panel. Here is how you can do it.
Quick-Tip: You will need a solar charge controller to measure PV current and voltage for this testing process.
Things You'll Need
- solar charge controller
- Rechargeable battery 12V
- Several connection cables
- Notebook and pen
Step 1. Connect the solar charge controller to the battery.
First, connect the battery to the solar charge controller.
Step 2 - Connect the solar panel to the controller
Then connect the solar charge controller and solar panel. Turn on the solar charge controller.
Quick-Tip: The solar panel must be placed outside where direct sunlight can reach the panel.
Step 3 - Calculate the number of watts
Scroll through the controller screen until you find the PV voltage. Write down this value. Then follow the same process and record the PV current. Here are the relevant values I got from my test.
Photovoltaic voltage = 15.4V
Photovoltaic current = 5.2 A
Now calculate the total watts.
Consequently, the
Solar panel power = 15.4 × 5.2 = 80.8W.
As you already know, for this demo I used a 100W solar panel. In the second test, I got a power of 80.8 watts. This value indicates the health of the solar panel.
Depending on the conditions, you may receive a different final answer. For example, you can get 55W for a 100W solar panel. When this happens, run the same test under different conditions. Here are a few things you can try.
- Place the solar panel where sunlight can directly contact the panel.
- If you previously initiated the test in the morning, try a second attempt at a different time (sunlight may be more powerful than in the morning).
Method 3: Test the solar panel with a wattmeter.
The wattmeter can measure power in watts directly when connected to a source. So no calculation needed. And you don't need to measure voltage and current separately. But for this test, you will need a solar charge controller.
Quick-Tip: Some recognized this device as a power meter.
Things You'll Need
- solar charge controller
- Rechargeable battery 12V
- Wattmetre
- Several connection cables
Step 1. Connect the solar charge controller to the battery.
First, take the solar charge controller and connect it to a 12V battery. Use the connection cable for this.
Step 2. Connect the wattmeter to the solar charge controller.
Then connect the wattmeter to the solar charge controller adapter cables. Once connected, the wattmeter must be in line with the controller. In other words, the two cables that connect to the solar panel must first be connected to the wattmeter. If you remember, in the previous test, the controller cables were directly connected to the solar panel. But don't do it here.
Step 3 - Connect the Solar Panel
Now place the solar panel outside and connect it to the wattmeter using the jumper cables.
Step 4 - Measure the power of the solar panel
Next, check the readings of the wattmeter. For this test, I got a reading of 53.7 watts. Given the sunlight, this is quite a decent result.
What we have learned so far
After checking your solar panel with one of the above methods, you will get a good idea of its performance. But remember, all three tests are different from each other.
In the first, we measured the voltage and current of the solar panel. The second method is based on a solar charge controller. Finally, the third uses a solar charge controller and a wattmeter.
Which method is the most suitable?
Well, it depends on your situation. For some, finding a wattmeter will be a daunting task. For example, some people may not have heard of a wattmeter and had no idea how to use it.
On the other hand, finding a digital multimeter or solar charge controller is not that difficult. So, I would say that the 1st and 2nd methods are the best. So, you will be better off with 1st and 2nd methods.
Why is solar panel testing so important?
Despite the fact that I mentioned this topic at the beginning of the article, I hope to discuss this issue in detail. So, here are a few reasons why solar panel testing is so important.
Recognize physical damage
Most of the time the solar panel will be outside. Therefore, it may be corrupted even if you don't know it. For example, small animals such as rodents can chew on exposed cables. Or the birds might drop something on the panel.
Testing is the best way to verify this. Whenever you bring in a new solar panel, test it the first time you start it up. This way you will know that the panel is working properly. If you find any output problems, check the solar panel again. Then compare the latest results with the results of the first test.
To identify corroded parts
Do not be surprised; even solar panels can corrode. It doesn't matter if you brought the world's best anti-corrosion solar panel. Over time, it can corrode. This process can greatly affect the performance of the solar panel. So remember to check it at regular intervals.
Determination of failed devices
In some cases, you may end up with a defective solar panel. The three tests above can be helpful in such a situation. As I mentioned earlier, it would be better if you could test the solar panel immediately after purchase.
To avoid fire hazard
Most often, solar panels will be installed on the roofs. Consequently, they will absorb a large amount of sunlight during the day. Because of this, the solar panels can overheat and cause a fire due to power failures. Therefore, to avoid such situations, check the solar panel regularly.
Warranty and regular maintenance
Due to the high usage and performance, these solar panels need to be serviced regularly. Most manufacturers provide these services free of charge during the warranty period. However, to get these benefits, you will need to test the solar panel from time to time. Otherwise, the warranty may become invalid. (1)
F.A.Q.
Can I test my solar panel on a cloudy day?
Yes you can. But this is not the method I would recommend. Due to clouds, sunlight will not reach the panel properly. Thus, the solar panel will not be able to show its full performance. If you are testing a solar panel on an overcast day, the results may mislead you into thinking that the solar panel is defective. But in fact, the panel works properly. The problem lies in the little sunlight. A clear and sunny day is the best day to test your solar panel. (2)
I have a 150W solar panel. But it only shows 110 watts in my wattmeter. Is my solar panel working correctly?
Yes, your solar panel is fine. Most solar panels give 70-80% of their rated power, so if we did the calculations.
(110 ÷ 150) x 100% = 73.3333%
Therefore, your solar panel is fine. If you need more power, position the solar panel in ideal conditions. For example, a place with the best sunlight can help. Or try changing the angle of the solar panel. Then measure the power of the solar panel.
Can I use a digital multimeter to test my solar panel?
Yes you can. Using a multimeter is one of the easiest ways to test a solar panel. Check the voltage and current and compare them with the nominal value.
Take a look at some of our articles below.
- How to test solar panels with a multimeter
- What are the positive and negative wires in a USB cable
- How to find a short circuit with a multimeter
Recommendations
(1) warranty period - https://www.sciencedirect.com/topics/computer-science/warranty-period
(2) clouds - https://scied.ucar.edu/learning-zone/clouds
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