Solar panel with strange ampere/watt behaviour

[kje]

I have an old panel, don't know how many watts.

The 2 first minute is normal but then the solar panels output is strange. The ampere/watt behaviour is jumping constantly after the 2 first minutes.

If I reconnect the panel it takes just seconds before the strange behaviour appear. If I wait e.g. an our befor reconnecting it behave normal for 2 minutes again.

I have changed the cable and checked the connections. What can be the reason for such behaviour?

 

[DThames]

Maybe a bad internal connection maybe. If you put some stress, like twisting on the frame a little, does it act differently?

 

[Hedges]

Panel, charge controller, battery, load?
State of charge of battery will cause charge controller to vary operating point of PV panel.
Try with a larger load connected to battery than what PV produces, so 100% of power is needed.

 

[kje]

I have checked the watt meter and the solar regulator, nothing wrong there.
Here is a video when the strange behaviour appears:

 

[kje]

Maybe a bad internal connection maybe. If you put some stress, like twisting on the frame a little, does it act differently?

I tried this without luck.
The fault has to be inside the solar panel. Is it possible to fix? Is there a way to look for weak spots?

 

[DThames]

Just curious.....after it is acting up, pour cool water on it (all over the panel) and see if the problem goes away while the panel is cooler.

 

[kje]

It looks like it happen when it reach a certain voltage. I suspect it's the solar chargers limit; when the voltage limit is reached the current drops and the strange behaviour appears. This is mayby normal?

 

[DurkaDurka]

Is this a single panel? Did you measure the open circuit voltage (12/24V panel)? What controller are you using?

 

[EricBarbour]

It looks like it happen when it reach a certain voltage. I suspect it's the solar chargers limit; when the voltage limit is reached the current drops and the strange behaviour appears. This is mayby normal?

it is quite possible for some cheap charge controllers to do this when the battery reaches full charge. But it could also be an intermittent defect in the panel. The way to be sure is to apply a fixed resistive load directly to the panel, with controller and battery disconnected, and monitor the panel voltage. Get a 10 ohm 25 watt power resistor and put it across the panel output. This one will work--you attach it to a chassis or heatsink with screws.

https://www.mouser.com/ProductDetail/TE-Connectivity-Holsworthy/THS2510RJ?qs=sGAEpiMZZMukHu%252BjC5l7YTh6kuZk5OeaMKUrCEpQ6u4%3D