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MC4 connector oxidation

J

Jordi

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Could not find such experience in this forum and wanted to share it with you.

Yesterday my solar panels produced much less kWh for what a sunny day should be like. Also I realized that during the sunset the PV arrangement voltage was almost zero while at that moment should be at least 20-30% of the VOC.

This morning I disconnected both panels as the issue persisted. Both were giving the right VOC individually and also in series. Finally I discovered that the connection of one MC4 connector was failing. The three MC4 pair of connectors are just 3 months old, or said in another way, have been exposed to the outdoor environment for 3 months. Despite of this short time, they are all significantly corroded already. I presume corrosion has been the rootcause for one of the connectors to disconnect. I have solved the issue by pushing the connectors against each other and remaking the connection but I am quite sure this problematic will hit back in the near future.

I think it is already too late to apply an effective solution given that corrosion has already started/happened, but I will try to clean the corrosion by scratching the metallic elements in the connectors and cover the connectors with plastic foil to isolate them as much as possible from rain, wind, etc...

My connectors are from Aliexpress. Probably they aren't made of stainless steel.
 
Jordi said:
Could not find such experience in this forum and wanted to share it with you.

Yesterday my solar panels produced much less kWh for what a sunny day should be like. Also I realized that during the sunset the PV arrangement voltage was almost zero while at that moment should be at least 20-30% of the VOC.

This morning I disconnected both panels as the issue persisted. Both were giving the right VOC individually and also in series. Finally I discovered that the connection of one MC4 connector was failing. The three MC4 pair of connectors are just 3 months old, or said in another way, have been exposed to the outdoor environment for 3 months. Despite of this short time, they are all significantly corroded already. I presume corrosion has been the rootcause for one of the connectors to disconnect. I have solved the issue by pushing the connectors against each other and remaking the connection but I am quite sure this problematic will hit back in the near future.

I think it is already too late to apply an effective solution given that corrosion has already started/happened, but I will try to clean the corrosion by scratching the metallic elements in the connectors and cover the connectors with plastic foil to isolate them as much as possible from rain, wind, etc...

My connectors are from Aliexpress. Probably they aren't made of stainless steel.
Click to expand...

Just my 2 cents worth. There is quality, acceptable quality and runbbish… rather than messing about with them buy some acceptable quality connectors and let that be the end of it for a good few years or pay top price for a few more years beyond that.

You could try some self fusing silicone tape to seal them.
 
Jordi said:
connectors are from Aliexpress
Click to expand...
Things are probably not adequate
Jordi said:
Could not find such experience in this forum
Click to expand...
I have posted about this issue several times.

Different brands of MC4s do not generally fit each other properly and leak water. That’s problem one.
Problem two that I solved with lexel was that the rubber compression sleeves for the wire into the fittings leaks.

I bought a large number of Bouge RV MC4s (because the don’t break readily in the cold). I disassembled every one and filled the wire entrance end with lexel and tightened back up. They’ll never come apart again but I haven’t had a failure since.
The Bouge seem to seal fine with the oring where they plug together. I was careful not use so much lexel that it squished into the plug-end of the fitting which would make them unremovable.

Again- I replaced every single MC4 with pairs from Bouge RV so they matched, AND I sealed the compression end.
 
I would be surprised if the contact surfaces in the MC4 connectors are stainless steel. I would expect them to be tinned copper. Stainless steel has a higher resistance than tinned copper.

I bought my MC4 connectors from TEMCoIndustrial.com and they worked fine, even connecting to the OEM MC4 connectors on my panels from Mission Solar. You could take the MC4 connector assembly apart and replace the crimp-on part. However, buying just the crimp-on part of the connector could be challenging. I couldn't find those on the TEMCo site so I contacted customer support and they hooked me up.
 
HRTKD said:
would be surprised if the contact surfaces in the MC4 connectors are stainless steel.
Click to expand...
They are at the least generally not magnetic. A very few I’ve seen have been!

These I thought would be magnetic by the color staining- but they are definitely not magnetic. image.jpg

The clean one was sold as fitting 8ga. Some say they aren’t available 8ga suitable, but the Bouge ones fit (I don’t need 8ga but I used 8 gauge mostly).

I tried to find those temco MC4s on their site but all I found was readymade cables with fittings that look like the renogy fittings.
It did bother my head that they carry clevises but they call them D-rings.
 
Last edited:
12VoltInstalls said:
They are at the least generally not magnetic. A very few I’ve seen have been!

These I thought would be magnetic by the color staining- but they are definitely not magnetic. View attachment 90931

The clean one was sold as fitting 8ga. Some say they aren’t available 8ga suitable, but the Bouge ones fit (I don’t need 8ga but I used 8 gauge mostly).
Click to expand...
That sure looks like iron rust.
Could be mud I suppose.
I like to assemble my mc4 with dielectric grease. Helps block out moisture.
 
Supervstech said:
That sure looks like iron rust.
Click to expand...
I know! But not magnetic.

They only thing I could figure is the barbed sleeve that normally holds these things in the fitting body must have been steel on the renogy fittings? Dunno
Dielectric turned to white powdery after a summer in the sun. I didn’t try the loktite brand but I think it’s better.
Been using Fluid film- and my next trial is going to be silicone faucet grease.
 
12VoltInstalls said:
I know! But not magnetic.

They only thing I could figure is the barbed sleeve that normally holds these things in the fitting body must have been steel on the renogy fittings? Dunno
Dielectric turned to white powdery after a summer in the sun. I didn’t try the loktite brand but I think it’s better.
Been using Fluid film- and my next trial is going to be silicone faucet grease.
Click to expand...
Good luck and let us know the results.
I like the convenience of MC4 connectors. But if any of mine fail, the repair will be solder and heat shrink.
No more issues.
 
Thank you all for your inputs and interesting discussion. I feared the cut-solder-heatshrink combo because If it goes wrong and you want to go back it's a big hassle but seeing some do it; for me, with a hobbyist installation (200W) makes sense. Problems gone forever.
 
Jordi said:
you want to go back it's a big hassle
Click to expand...
True. That’s why I stay married to MC4s. I change stuff around often enough and I’ve solved the water ingress issues so it’s not a concern to me.
 
A.Justice said:
I wonder if there was something with iron in it, uphill from the wire, that dripped rust water down the cable over a long period.
Click to expand...
It might have been the clip inside that retains the fitting conductor was steel
 
Last edited:
12VoltInstalls said:
They are at the least generally not magnetic. A very few I’ve seen have been!

These I thought would be magnetic by the color staining- but they are definitely not magnetic. View attachment 90931

The clean one was sold as fitting 8ga. Some say they aren’t available 8ga suitable, but the Bouge ones fit (I don’t need 8ga but I used 8 gauge mostly).

I tried to find those temco MC4s on their site but all I found was readymade cables with fittings that look like the renogy fittings.
It did bother my head that they carry clevises but they call them D-rings.
Click to expand...
I have a house near the sea, and by near I mean practically in it, even 316 Stainless Steel gets an orange hue overtime and it won't be magnetic
 
Mike 134 said:
Question is what seal failed to allow water inside? Cable grip on the end not tight enough/wrong size?
Click to expand...
What I found initially was different ‘brands’ don’t fit each other well for the oring to seal. When I had low/no volts incoming I went exploring, cuz when I did it was jumping all over the place

I started cutting, examining, replacing. What I determined is the ‘rim’ part of the tophat-shaped rubber compression seals (where they seal against the face of internals of the MC4) would apparently not consistently sit flat and seal. I suspect the compression seal on the wire sheathing is fine when tightened. The “gasket” seal against the MC4 seemed to show staining that indicated less than 100% contact. With the wide heating/cooling temps in Vermont I think it was allowing water to be drawn into the fittings and subsequently the wires.
bruce_loco said:
Do you live near the sea?
Click to expand...
Vermont. 1600’

*Anyway, by sealing under every single one of the compression nuts with lexel- problem appears solved.
 
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