Use a multimeter to check the polarity of the panel.View attachment 196151
Should be fine on that basis <24v…I’m going direct from panel to ctek (no controller) and using an extension to the wires that came provided, I had to crimp and heat shrink larger lugs to fit the ctek.
panels work fine when plugged in via controller to charge phone etc.
Not sure what I should be testing next!!
Sometime they wired back to front.
You should see +15-22v DC from the panel in strong daylight/sun.
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Post some pics of the multimeter with the panel off the ctek.
Then connected to the ctek.