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Solar panels are basically set and forget. Once installed, the system produces power without needing any input from you. But what happens if the solar panel has no voltage or very low power? What should you do? These are actually common problems and there are ways you can fix them.
A faulty inverter or charge controller are the most likely reasons for a solar panel to register no voltage. Other possible reasons for low to zero power are a damaged PV module, poor wiring, shading and temperature higher than the ideal operating range.
Troubleshoot Solar Panels with No Voltage
If your solar array does not produce any voltage or power, these are the three most probable reasons:
- Damaged charge controller
- Damaged inverter
- One or more of the solar panels in the array is malfunctioning
How to Test a Solar Panel
Solar panel warranties usually guarantee operation up to 25 years. But wear and tear could damage one or more of the arrays. The best way to find out is to test the system.
PV Open Circuit Voltage (VOC) Test. Get a multimeter like the AstroAI 2000 and set it to measure DC. Disconnect the solar panel from the system and connect the negative lead of the multimeter to the negative terminal of the solar panel. Repeat this step with the multimeter positive lead with the panel positive terminal.
The Open Circuit Voltage should display the following:
- 24V PV modules: 34V to 56V
- 12V PV modules: 18V to 28V
PV Short Circuit Current (ISC) Test. Disconnect the solar panel from the rest of the system. Set the multimeter to check for current (A). The minimum setting is usually 10A. Connect the multimeter positive wire to the panel positive terminal. Repeat this step with the multimeter negative wire and the negative panel terminal.
Depending on the solar panel specifications, the results should be between 3A to 9A. This number could vary depending on how your solar array is configured.
How to Load Test a Solar Panel. You can connect a TV and a fan to a solar panel to test if it is working. But there is an easier way. Get a couple of 12V light bulbs, around 20 watts each. Hook up the bulbs’ wires to the negative and positive terminals on the panel. The bulbs should light up.
If your solar panel fails any of these tests, it is a sign there is probably something wrong with it. You have to do more solar panel repair or call a professional installer to repair or replace it.
How to Test a Charge Controller
Connect the multimeter positive test lead to the positive wire on the charge controller. Do the same for the negative multimeter lead and the negative solar controller wire. The multimeter will display how much current is going through the system.
If there is no current or there is an error message, reset the charge controller. If that does not work, disconnect the controller from the solar power system. Reconnect all the cables and try it again. If nothing happens, the controller is damaged.
How to Test an Inverter
There are many types of inverters but they all have built -in mechanisms that make system monitoring easy. The following are some of the most common methods manufacturers use, plus other ways you can determine if something is wrong.
Warning lights. Solar inverters will flash warning lights if there is a problem. If your solar array has no voltage, check the inverter. If the lights flash, reset the inverter . If that does not work, disconnect the unit from the solar system and reconnect the wires after a few minutes.
Noise. The only sound you should hear is a click when you turn it off or on. There may be a slight hum, but others do not even produce that. If there are other noises coupled with zero solar panel power, the inverter has a defect.
Monitor performance. Powerful inverters have data trackers so you can check how much power is being generated. If you have been using your inverter for a while now, you will know how much power it pulls from the solar system or battery.
The power draw fluctuates according to the season, time of day, appliances used etc. But if the performance suddenly drops and you have ruled out these possibilities, the inverter may need repair or replacement.
Troubleshoot Low Voltage Solar Panels
Is your solar panel not performing as well as it used to? Is the power generation dropping quickly for seemingly no reason? Low power is a very common solar array problem, and fortunately, the fix is usually easy.
Most solar panels do not need cleaning, as rainfall is sufficient to wash off dirt. But if you live in a dry area, dirt, dust and other airborne particles may have accumulated on the panel. In this case cleaning solar panels is a necessity.
If your solar array is connected in a series, one poor performing solar panel will affect the rest of the array. By cleaning the cells you might be able to get the PV array running at full power again.
This is the most likely cause of low solar power output. All PV arrays must be installed with a clear, unobstructed view of the sun. Trees, buildings or any objects that block it will cause a drop in voltage and energy production.
Perform an inspection at least twice a year especially if there are any trees nearby. Even if you trimmed the branches, it does not take long for tree branches and foliage to grow back. You should also check the array following a storm as debris may have been blown all over the cells.
If you live in a dusty, arid area, sand, dust and other particles could pile on the cells quickly. Hose them with water if possible or call a professional solar cleaning service to do it for you.
If your solar panel, inverter and charge controller are not faulty, the most likely reason is poor connection. Use a multimeter to check the connection points at various areas of the solar system. You should get a reading if the connection is stable.
Also look for signs of frayed or loose wires. There might also be a blown fuse somewhere. Any one of these can trigger a voltage drop and reduce output even if the sun is out. Frayed wires can also be dangerous and could start a fire or just stop working. If there are loose wires, tighten them right away. You can also replace them with new solar panel wiring like the Kohree 10 AWG solar panel cables to ensure efficient performance.
Solar panels are designed to operate under specific temperature ranges. If it gets too cold or too hot, the panels will still run, but it will not be under optimum conditions. This can result in gradual or sudden voltage drops.
A very persistent solar power myth is that the hotter it is, the more efficient a solar panel will be. That is not true. PV modules do not perform better during hot days. In fact, the higher the temperature goes, the higher the odds the voltage will drop.
If you notice the solar array voltage dropping, check the temperature. If it is higher than normal, then you have the probable cause. Solar power works fine without excessive heat. What it needs is the energy of the sun, because heat actually cause the cell temperature to rise. Overheating is not good for solar panels.
The best solution is to add more panels to your array. Connect the panels in a series or parallel and that should eliminate the overheating problem. You could also reduce the load when the temperature is high. If you are not using the modules, put a solar panel cover on them.
Defective PV Modules
This is unlikely especially if you bought them from a reputable manufacturer. But it is worth considering if all others failed. Check the solar panels for signs of cracks, hot spots, UV discoloring or even water seeping into the system. You can perform solar panel troubleshooting, but if it is severe, you need to contact a professional solar panel technician to assess the damage and if it can be repaired or if it needs to be replaced.
If the solar panel is still under warranty, you may be able to get it replaced at no cost. But this will depend on the damage and if it falls under the warranty coverage. This is why it is crucial that you take the time to study the warranty so you can determine what it does and does not cover.
Solar panel systems have earned a reputation for being low maintenance and easy to manage. These are well deserved, though sometimes problems can occur like low to zero voltage. When they do occur, the fixes are often simple like the ones given here. Of course if you are not familiar with wires and do not like tinkering, there are technicians you can call.