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MC4 connectors a massive scandal

Spent sometime this past weekend replacing several more MC4's. Out of the ones I replaced I only found 2 more that showed considerable corrosion. They were on the first set of feeder PV wire I bought from an Amazon retailer back 5-6 years ago that I used to bring in power to a micro grid tie "pirate" setup I had back then. That did not last for long and the PV wire was then put into service on my #1 Array that has seen quite a few changes. I had not noticed any problems with them in terms of how they worked but I expect it was only a matter of time until they failed with the level of corrosion they have.

One thing after doing this that comes to mind is; I wonder how many solar installations that folks have that have bad MC4's and they do not know it?
 
Mattb4 said:
Spent sometime this past weekend replacing several more MC4's. Out of the ones I replaced I only found 2 more that showed considerable corrosion. They were on the first set of feeder PV wire I bought from an Amazon retailer back 5-6 years ago that I used to bring in power to a micro grid tie "pirate" setup I had back then. That did not last for long and the PV wire was then put into service on my #1 Array that has seen quite a few changes. I had not noticed any problems with them in terms of how they worked but I expect it was only a matter of time until they failed with the level of corrosion they have.

One thing after doing this that comes to mind is; I wonder how many solar installations that folks have that have bad MC4's and they do not know it?
Click to expand...
Any pics? Wondering what type and how bad the corrosion is I don't bother with mc4 on my combiner box so it's just at the panels for now but I live in humidity land so I tend to build things with that in mind(very few IP rated things on favour of drain holes I see to many so called IP rated lights/enclosures that eventually become fishbowls as they let in humid air but can't let out the trapped condensation).
 
Mattb4 said:
Spent sometime this past weekend replacing several more MC4's. Out of the ones I replaced I only found 2 more that showed considerable corrosion. They were on the first set of feeder PV wire I bought from an Amazon retailer back 5-6 years ago that I used to bring in power to a micro grid tie "pirate" setup I had back then. That did not last for long and the PV wire was then put into service on my #1 Array that has seen quite a few changes. I had not noticed any problems with them in terms of how they worked but I expect it was only a matter of time until they failed with the level of corrosion they have.

One thing after doing this that comes to mind is; I wonder how many solar installations that folks have that have bad MC4's and they do not know it?
Click to expand...
A lot.
Special company that try to save on those plugs.
Cheap panels have cheap plugs .

So i do think a lot of people do not know.
Well the company that sell plugs and panel tell you that its 25 years maintenance free
Wel yes if you have a brand that have certification on those mc4 plugs and panels.
 
ThaiTaffy said:
Was it galvanic or just simple old rust on cheap steel contacts?
Click to expand...
Copper corrosion of loose gray/whitish powder with green verdigris. No rust that I can remember. You would think the tin coating would prevent that.
 
Mattb4 said:
Copper corrosion of loose gray/whitish powder with green verdigris. No rust that I can remember. You would think the tin coating would prevent that.
Click to expand...
so galvanic, i wonder what reacted, I'm guessing the mc4 conductors are tinned what about the cable? was that tinned? in theory tinned copper shouldn't corrode but just the act of crimping will break the conductors coating and make it more porous (susceptible to corrosion). good info though makes me think i might goop all my crimps not just battery terminals.
 
Has anybody tried gooping the mc4 connectors when initially hooking everything up?

What kind of goop would work best for these conditions, considering the high voltage, outdoor conditions involved in many solar panel connections?
 
cs1234 said:
Has anybody tried gooping the mc4 connectors when initially hooking everything up?

What kind of goop would work best for these conditions, considering the high voltage, outdoor conditions involved in many solar panel connections?
Click to expand...
Once you've made the crimp I'd think dielectric would be fine in the back of the housing.
 
I think just a dielectric grease, but sealed volume means trapped air.
What would be better is something that could have grease injected through after assembly.

I'm finding grease-filled crimps, and grease tubes to put over crimps, but so far only < 50V, e.g. for irrigation.
Something like this should work well for PV, if rated for the voltage.

Grease Filled Crimp | RCL Irrigation Ltd

Electrical grease filled connector are an ideal solution for connecting cables with areas that could be susceptible to damp conditions. Available in Red, Or ...
www.rclirrigation.co.uk www.rclirrigation.co.uk


Some junction boxes have push connectors, aren't soldered. Potential for similar failures.
I got a surplus carton, and remove the wires when I need pigtails.
 
Hedges said:
I think just a dielectric grease, but sealed volume means trapped air.
What would be better is something that could have grease injected through after assembly.

I'm finding grease-filled crimps, and grease tubes to put over crimps, but so far only < 50V, e.g. for irrigation.
Something like this should work well for PV, if rated for the voltage.

Grease Filled Crimp | RCL Irrigation Ltd

Electrical grease filled connector are an ideal solution for connecting cables with areas that could be susceptible to damp conditions. Available in Red, Or ...
www.rclirrigation.co.uk www.rclirrigation.co.uk


Some junction boxes have push connectors, aren't soldered. Potential for similar failures.
I got a surplus carton, and remove the wires when I need pigtails.
Click to expand...
You could try to inject dielectric into a mated connector before tightening the gland on each end but it seems like it would be messy and a pita if you ever needed to disconnect and reconnect later.
 
ThaiTaffy said:
You could try to inject dielectric into a mated connector before tightening the gland on each end but it seems like it would be messy and a pita if you ever needed to disconnect and reconnect later.
Click to expand...
Why not just use marine butt connectors that shrink on? Readily available and bullet proof.
If you need to replace a panel, cut and reconnect.
I didnt know that there were so many issues with the MC connectors.
 
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Dave911 said:
Why not just use marine butt connectors that shrink on? Readily available and bullet proof.
If you need to replace a panel, cut and reconnect.
I didnt know that there were so many issues with the MC connectors.
Click to expand...
Not really going to prevent galvanic corrosion the air is already in the fitting and the mixture of metals is what's causing it you need to expel any air around the crimp to prevent it, if using heat shrink around the crimp there's a good chance it wouldn't fit into the body then.
 
Hedges said:
I think just a dielectric grease, but sealed volume means trapped air.
What would be better is something that could have grease injected through after assembly.

I'm finding grease-filled crimps, and grease tubes to put over crimps, but so far only < 50V, e.g. for irrigation.
Something like this should work well for PV, if rated for the voltage.

Grease Filled Crimp | RCL Irrigation Ltd

Electrical grease filled connector are an ideal solution for connecting cables with areas that could be susceptible to damp conditions. Available in Red, Or ...
www.rclirrigation.co.uk www.rclirrigation.co.uk


Some junction boxes have push connectors, aren't soldered. Potential for similar failures.
I got a surplus carton, and remove the wires when I need pigtails.
Click to expand...
These are cheap and nasty 50p each barely suitable for 24v ac <1A toy solenoid valves used for garden irrigations systems hardly relevant to Solar systems
 
Dave911 said:
Why not just use marine butt connectors that shrink on? Readily available and bullet proof.
If you need to replace a panel, cut and reconnect.
I didnt know that there were so many issues with the MC connectors.
Click to expand...
Are you referring to these, how is this relevant to 10AWG solar cable/MC4s
 

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    image_2024-07-09_043709782.png
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Boron said:
Are you referring to these, how is this relevant to 10AWG solar cable/MC4s
Click to expand...
Im not sure what the od is of 10 gauge solar cable, but they work fine with 10 gauge THWN.
Im saying dont use MC4s, cut them off and use heat shrink butt splices.

Something like this.
www.menards.com

Gardner Bender® Xtreme 12-10 AWG Yellow Butt Splice - 3 Count

The Gardner Bender® Xtreme Series Terminals are constructed with heat-shrink insulation and are adhesive lined to waterproof and environmentally-seal electrical connections when crimped and heated. These terminals insulate and protect connections from wire pullout, moisture intrusion, and...
www.menards.com www.menards.com

This price is high, but others make them and sell them in larger quantities.
 
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Reactions: JRH
Dave911 said:
Im not sure what the od is of 10 gauge solar cable, but they work fine with 10 gauge THWN.
Im saying dont use MC4s, cut them off and use heat shrink butt splices.

Something like this.
www.menards.com

Gardner Bender® Xtreme 12-10 AWG Yellow Butt Splice - 3 Count

The Gardner Bender® Xtreme Series Terminals are constructed with heat-shrink insulation and are adhesive lined to waterproof and environmentally-seal electrical connections when crimped and heated. These terminals insulate and protect connections from wire pullout, moisture intrusion, and...
www.menards.com www.menards.com

This price is high, but others make them and sell them in larger quantities.
Click to expand...
I would probably put a second shrink sleeve over those if I was going to run near 600 volts DC. They are truly watertight. I have them submerged in the bilge of my boat to power the bilge pumps.

Life is too short to use bad connectors.
 
ThaiTaffy said:
Not really going to prevent galvanic corrosion the air is already in the fitting and the mixture of metals is what's causing it you need to expel any air around the crimp to prevent it, if using heat shrink around the crimp there's a good chance it wouldn't fit into the body then.
Click to expand...
Dave911 said:
I would probably put a second shrink sleeve over those if I was going to run near 600 volts DC. They are truly watertight. I have them submerged in the bilge of my boat to power the bilge pumps.

Life is too short to use bad connectors.
Click to expand...
I agree…very simple and easy…last a very long time …..I have used these for hundreds of boating connections.. in dry places they are probably fine alone ,…. in sorta wet places , I would add a second sleeve of heat shrink too….. for long term underwater usage like sailboat bilge/ sump pumps or critical wet places , I used to add a good wrap of self amalgamating waterproof tape as a tat of insurance..

This is what I’m doing now for my new panel arrays .. iI am leaving about a foot of slack PV wire so as to be able cut them off if need be two or three times and have easy wire to re-connect.

I know…it’s a bit overkill ,but it works..
 
JRH said:
I agree…very simple and easy…last a very long time …..I have used these for hundreds of boating connections.. in dry places they are probably fine alone ,…. in sorta wet places , I would add a second sleeve of heat shrink too….. for long term underwater usage like sailboat bilge/ sump pumps or critical wet places , I used to add a good wrap of self amalgamating waterproof tape as a tat of insurance..

This is what I’m doing now for my new panel arrays .. iI am leaving about a foot of slack PV wire so as to be able cut them off if need be two or three times and have easy wire to re-connect.

I know…it’s a bit overkill ,but it works..
Click to expand...
Once I stop rearranging and improving my setup I likely will go to a better connection than the MC4's perhaps similar to this method. My Thanks to the OP to bring up the issue of faulty over time MC4's
 
Dave911 said:
Im not sure what the od is of 10 gauge solar cable, but they work fine with 10 gauge THWN.
Im saying dont use MC4s, cut them off and use heat shrink butt splices.

Something like this.
www.menards.com

Gardner Bender® Xtreme 12-10 AWG Yellow Butt Splice - 3 Count

The Gardner Bender® Xtreme Series Terminals are constructed with heat-shrink insulation and are adhesive lined to waterproof and environmentally-seal electrical connections when crimped and heated. These terminals insulate and protect connections from wire pullout, moisture intrusion, and...
www.menards.com www.menards.com

This price is high, but others make them and sell them in larger quantities.
Click to expand...
And how save are those connectors .
Fine for 48 volt but higher i will not trust it.

I will not run 250/500/1000 volts .
Its not designed for it.


Than you can go for the pv4 connector

www.te.com

SOLARLOK PV4-S DC Crimp Connectors

Our SOLARLOK PV4-S DC Crimp Connectors are designed to connect solar panels to the power grid, and are adapted for 1500VDC cable solutions. Applications include solar and micro inverters, combiner boxes and DC optimizers.
www.te.com www.te.com

1500volts and are for solar panels
 

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Suijkerbuijk said:
And how save are those connectors .
Fine for 48 volt but higher i will not trust it.

I will not run 250/500/1000 volts .
Its not designed for it.
Click to expand...
1720533969869.png

It's listed for 600 volts. It's jacket is rated for 600 volts. It's a piece of metal that is crushed onto other pieces of metal. As long as there is a solid link between the two ends of wire and the connector, what does the voltage have to do with it? It's not a switch or breaker, it does not have to safely extinguish an arc.

I would think the main concern is what kind of amperage it can handle.. but it's designed for 10awg, so I would assume it can handle the same amperage that 10awg would.
 
cs1234 said:
View attachment 227446

It's listed for 600 volts. It's jacket is rated for 600 volts. It's a piece of metal that is crushed onto other pieces of metal. As long as there is a solid link between the two ends of wire and the connector, what does the voltage have to do with it? It's not a switch or breaker, it does not have to safely extinguish an arc.

I would think the main concern is what kind of amperage it can handle.. but it's designed for 10awg, so I would assume it can handle the same amperage that 10awg would.
Click to expand...
Its not against uv .
And that is a problem if sunlight will damage the outside.
Those things are use for inside .

I will not use it .
Insurance will have big smile if your roof is burn .
And see that u using somting that is not designed for.
 
Suijkerbuijk said:
Its not against uv .
And that is a problem if sunlight will damage the outside.
Those things are use for inside .

I will not use it .
Insurance will have big smile if your roof is burn .
And see that u using somting that is not designed for.
Click to expand...
If your roof catches fire I doubt they will tell the difference between a mc4 and a crimp it's all likely to be ash.
 
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