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 > Solar Panel, Unmarked Pigtails, which is Positive, Negative?

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ktmrfs

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Posted: 01/07/20 09:06pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

naturist wrote:

You will note that they have MC4 connectors on them. Those connectors are one male, the other female. It is impossible to connect them wrong because of the MC4 connectors. That is why they are there in the first place. But also, a VOM will confirm they are wired correctly.


If you use the clips as I linked above, and put them on the wrong wires going to the controller, you can end up with them reversed. Those little monsters take a bit of figuring out. [emoticon]

Once they are on you can't get them off either. The pin grabbers mean once in, they stay in. It is an IQ test. If you fail the IQ test you buy more clips!


I've got MC4's on my portable panels and my home made parallel/series connector setup. MC4's are pretty easy to unsnap even w/o any tools. I don't even need any tools, I can easily do it with my fingers. Or you can use the plastic tool made for disconnecting MC4's.


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BFL13

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Posted: 01/07/20 09:14pm Link  |  Quote  |  Print  |  Notify Moderator

Yes the MC4s unsnap easily, but the metal pin in the ones I showed that you have to assemble onto a wire, have those little one-way grabbers that don't come back out once you shove them in.

The links I gave show a photo of the metal pin with its little grabbers, which keep the wire from being pulled out of the MC4 once assembled.

There might even be a proper name for what I am calling "grabbers" [emoticon]


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crcr

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Posted: 01/08/20 06:20am Link  |  Quote  |  Print  |  Notify Moderator

Thanks to Everyone for your prompt responses! Much appreciated. I will take the panels into the sun today and use a volt meter to verify that the MC4 connector with the red ring is positive.

Bill.Satellite

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Posted: 01/08/20 08:33am Link  |  Quote  |  Print  |  Notify Moderator

While I suspect that the information above is correct about which is positive, the best advice is to check the connections with a multimeter. Set the panel in the sun and put your probes on the 2 connections. If you have red to red and black to black you will see a 12V (or whatever) reading. If you have it backward you will see -12V.


What I post is my 2 cents and nothing more. Please don't read anything into my post that's not there. If you disagree, that's OK.
Can't we all just get along?

ktmrfs

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Posted: 01/08/20 11:54am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

Yes the MC4s unsnap easily, but the metal pin in the ones I showed that you have to assemble onto a wire, have those little one-way grabbers that don't come back out once you shove them in.

The links I gave show a photo of the metal pin with its little grabbers, which keep the wire from being pulled out of the MC4 once assembled.

There might even be a proper name for what I am calling "grabbers" [emoticon]


ah, yes, now that I understand better, you are correct. once the pins go in the housing, they are almost impossible to remove. I say almost because there is a tool that will slide over the metal part inside the mc4 and push down to release the "grabbers" and let you pull the pin out. But it takes some finese and force to do it. So it's best to get the pins in the correct sex housing on the first try. Or your likely to have to cut the wire and repeat.!

bpounds

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Posted: 01/08/20 02:44pm Link  |  Quote  |  Print  |  Notify Moderator

Look very closely at your MC4 connectors. Most have a + or - molded into the body. It's really only an issue if you start making your own cables as I did. But checking your work as well as the manufacturers work is always time well spent.

What makes the MC4 connectors extra confusing, is that the gender of the conductor pins are opposite of the connector body. So when someone refers to a M or F, you are left wondering if they mean the gender of the pin, or the body. But it's all part of the fun.


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wa8yxm

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Posted: 01/08/20 05:54pm Link  |  Quote  |  Print  |  Notify Moderator

I second the voltmeter suggestion but I also notice two "Barrel shaped" electroinc components in the box connected end to end.

These devices have a sliver band on one end In both cases the band is on the RIGHT side as it's photographed.

These are reverse polarity diodes. designed to SHORT the leads if you hook up to a battery backwards and blow the fuse.. So the banded end needs to be POSITIVE or they conduct and pop-a-fuse.. be sure to fuse 'em.

But by all means confirm this by use of a voltmeter cause.. I've seen diodes marked backwards.


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BFL13

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Posted: 01/08/20 06:23pm Link  |  Quote  |  Print  |  Notify Moderator

crcr wrote:

Thanks to Everyone for your prompt responses! Much appreciated. I will take the panels into the sun today and use a volt meter to verify that the MC4 connector with the red ring is positive.


The OP must have got sun-stroke and zapped himself as well, or we would have heard back by now how that went. [emoticon]

crcr

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Posted: 01/08/20 07:50pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

crcr wrote:

Thanks to Everyone for your prompt responses! Much appreciated. I will take the panels into the sun today and use a volt meter to verify that the MC4 connector with the red ring is positive.


The OP must have got sun-stroke and zapped himself as well, or we would have heard back by now how that went. [emoticon]


LOL, no sun stroke. I got a chance to test one of my three Renogy panels, and as expected by my many helpful friends on this forum, the pigtail with the red band is in fact, the positive lead. As is wont to happen, life then intervened and I didn't get a chance to test the other two panels. Most likely the polarity is the same on those as the first panel, but just to be thorough, I will test the other two panels tomorrow and report back.

crcr

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Posted: 01/08/20 08:01pm Link  |  Quote  |  Print  |  Notify Moderator

I have another related question and since it is about the mounting of solar panels on an RV roof, I will ask it in this thread rather than start a new thread.

I have stainless steel hardware to fasten the solar panels to my RV roof. Since stainless steel is known to sometimes gall, would it be wise to use a little bit of Anti-Seize on the SS nuts and bolts when assembling them? The pic below is of some copper-based anti-seize that I happen to have.

[image]

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