MPPT250 70 PV voltage on cooling fins grounding point

DIY
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3

Hi,

thanks for your thoughts on that. I checked the PV with an insulation tester. It looks completely fine.

I build a small test setup to check the MPPT. I used a 12V car battery and a single PV panel with about 45V open circuit valtage.

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With that setup i also measured PV voltage between the negative battery terminal and the grounding point.

IMG_20250519_092914
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When i connect the grounding point to the negative terminal on the battery, there are no sparks and the current through the grounding wire is <1mA. It seems like the sparks only appear with higher PV voltage.

I did the same measurement with a different MPPT and there is no voltage between the negative battery terminal an the grounding point.