Guru
Joined: 31/12/2016
Location: AustraliaPosts: 1267
| Posted: 09:25am 18 Jun 2025 |
Ok then, check each section with a meter while in full sunlight and see if anything isn't right, diodes etc, testing each section under some load should be helpful, I have found a few faulty panels but they were all old, some look good when reading short circuit current but didn't put out any useful power at VMP, thought that was a bit strange, haven't got around to fixing yet.
Just for an example using an old panel, 250w 60 cell open circuit voltage 38v, well it used to be.....not very sunny today so panel voltage is 35v total, this panel output will stop completely if any portion of it is shaded, and would be useless on its own, if it were in a string the rest of the panels should still work through the bypass diodes........I normally don't bother with any of this detail just connect a string of 3 for the MPPT charge controller and power on......lets go.....
Now disconnecting one section (see line drawn on lower panel string) in the junction box and left the diode in place, the panel will now output 23.2v and the other section is 11.6, now we can shade the lower section and it has no affect on the rest of the panel, there is normally no reason to do this (just a demonstration) but I can use this to charge a 12v battery with an appropriate charge controller
A little info on the diodes and how they are used..https://sinovoltaics.com/learning-center/off-grid/blocking-diode-bypass-diode-solar-panels/ you may have seen this already but if you haven't
or it might be useful for someone else.
