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

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. :(

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!

Funny, I've had no trouble distinguishing the male from the female MC4 connectors, nor for that matter, taking them apart after once putting them together. All you have to do is squeeze at the right spot, and they come right apart.

As for at the controller, when you make your own connectors, you certainly can put the wrong MC4 gender plug on there. One must certainly pay attention. But I defy you to plug two males or two females together. Homosexuality just isn't a thing with MC4 connectors.

crcr wrote:

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. :)

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.

Follow-up: I did test the 2nd and 3rd panels of the same brand (Renogy) today, and the MC4 connector with the red ring is the positive pigtail on all three solar panels.

Thanks again, everyone, for your helpful responses. Much appreciated!

crcr wrote:
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.

On an RV, I'd be more concerned about fasteners coming loose.

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.

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. :)

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 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. :)

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.

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.

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" :)

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.!

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.