question

skykay avatar image
skykay asked

250/100 mc4 not working

Hi I set up 4 375w panel in series and installed the cables on the first mc4 switches. All working fine. Then I put a second series same panel but only on in series on the second mc4 connector. The 250/100 stopped working...showing only 0-6 watts. Did I destroy it because of 2 different strings? thanks

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4 Answers
klim8skeptic avatar image
klim8skeptic answered ·

Sounds like you have reverse polarity connected the second string.

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rickp avatar image
rickp answered ·

I agree with @klim8skeptic on this. Your first set of panels is fine, and should be about 120-160v and about 10a or so. I don’t understand exactly what your second string consists of... one panel? You say in series, so I’m not sure. Your connection to the second MC4 set puts that string in parallel to the first string, but should still be ok if it’s just 1 or 2 panels. Check your wiring on both ends. Sounds like something is reversed somewhere.

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skykay avatar image
skykay answered ·

I have 2 string with 4 panels each in series. Polarity is fine. I checked it several times. (see attached pictures) And when I plug in the cabels from the former working string nothing happens.


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ejrossouw avatar image ejrossouw commented ·

@skykay For the sake of clarity. Did you connect the first string to the controller using the first set of MC4 and then added the second string to the second PAIR of MC4 connectors? All I can think is the panels were energized at the time and you should not connect live wires as this could well have damaged the controller or blown the internal fuse. Otherwise check the fuse between the battery and the charge controller, assuming you have one. Fuses featured a lot in recent posts.

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skykay avatar image
skykay answered ·

Ok, I am sending it back to have it repaired...thanks

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