Looking for advice on cables and connectors for solar panels

[Jacob Cambridge]

Hello, I am wondering if anyone can offer advice on solar panel cables and connectors. I wrote an earlier post about affixing flexible panels to my metal roof. For my next trick I need to run extension cables from those panels under the roof and into the house. The easy solution would be to buy premade extension cables. There are a number of vendors selling these on Amazon. My concern is about quality. These will be hard for me to service. Does anyone have any suggestions?

I would be grateful for specific manufacturers or suppliers or just advice.

Thanks.

[SunEagle]

I found that making my own cables can be chancy if I do not have the proper tools. I have purchased a number of pre-made cables and they seem to have lasted a long time but they really haven't been moved around much or have seen direct sunlight so maybe I have extended their life by protecting them somewhat.

[bcroe]

Hello, I am wondering if anyone can offer advice on solar panel cables and connectors. I wrote an earlier post about affixing flexible panels to my metal roof. For my next trick I need to run extension cables from those panels under the roof and into the house. The easy solution would be to buy premade extension cables.

If you want MC4 extensions just the right length, make them yourself and perhaps save
money as well. MC4s are pretty cheap, you need a cheap crimper and I recommend
putting some NO-OX on the contact to increase its life. DO NOT leave MC4s exposed
at all to the weather, without noble metal they will quickly start oxidizing. No solar wire
handy, you could buy one long extension and cut it into the short pieces you need.
good luck, Bruce Roe

[khanh dam]

any dc wire that penetrates the roof must be in metal conduit to meet code. better talk to your AHJ and figgure something out before hand before it becomes a nightmare to redo. Mc4 crimp tool is $10 the connectors are $1 cheap to diy and easy, make sure you buy a removal tool as well. to unclip any accidental connections. they are $3

[Jacob Cambridge]

Thanks, everyone. Do you think I can pick up MC4 connectors on Amazon or do I need to worry about low quality off-shore manufacturing? In other words, is their much variation between MC4 connector brands and manufacturers?

[khanh dam]

unless you can find copper ones, the only ones I've seen are crappy aluminum, thus the recommendation above for Nox paste to keep the flow of electrons going 10 years latter.

[bob-n]

Amphenol makes excellent MC4 connectors, copper with tin plating. They call them Helios H4. A large industrial distributor called Mouser sells them for between $1.32 and $2.90 each, depending on exact model. This link searches Mouser for all in-stock H4 connectors:

https://www.mouser.com/Connectors/Solar-Connectors-Photovoltaic-Connectors/_/N-79syi?Keyword=amphenol+h4&FS=True

From personal experience, both Amphenol and Mouser are excellent companies.
Usual disclaimer: no affiliation, just trying to help.

You will also need a crimper. The Amphenol crimper is excellent and very expensive. There are imported ratcheting crimpers on Amazon for $25 or so that may be adequate. They are certainly better than simple crimper/stripper/bolt cutters sold for $5-$10. It is critical to get a crimper with the right size jaws for the connector.

[Jacob Cambridge]

https://www.mouser.com/datasheet/2/18/1/IDS_17_Helios_H4-865.pdf

Does this look like the right part?

[bob-n]

yes

[chrisski]

I really don’t see a way around making your own cables. The premade cables have the MC4 connector on and you’d need to either drill a larger hole or get a thicker conduit to stuff it in. Making them yourself is not hard at all. I got 100’ of wire for my RV build thinking I’d need 70’, but actually used 90’. Often times when putting the wire down. the shorter route I had planned was not usable for some reason.

any dc wire that penetrates the roof must be in metal conduit to meet code.

Electric PVC pipe would not work? If I remember right PVC pipe is for burying cable and for outdoor use, but metal needs to be used inside.

[solarix]

Be careful with MC4 connectors. There are lots of manufacturers of them now and they are not all perfectly compatible. And if you have connection problems, you could have nightmare arc-fault issues. I do not like the cheap MC4 connectors with contacts made from stamped sheet metal. Pretty flimsy. I only trust the machined solid contacts ($$$) with swagged crimps. I was amazed years ago to discover that even though MC4 connectors seemingly have these big contacts, in reality there is only about 1/4" engagement (at best) of the contact tips when plugged together. If you don't fully plug the connector together, or use connectors from different manufacturers (some PV panel makers use some pretty weird MC4s), there can be intermittent connections (that will drive you nuts trying to find). There was a good article in SolarPro magazine a few years ago that tested different combinations of MC4s and found they are not all compatible.

[Jacob Cambridge]

Great feedback everyone. I'm inclined to buy Amphenol connectors. In my experience with other types of cabling, they do things right. What about crimping tools? Amphenol sells a crimper for a few hundred bucks. Meanwhile, there are dozens for sale in the $25.00 range. I'm not likely to do this one job and hopefully never need to crimp again!

[bob-n]

Unfortunately, Amphenol's crimper is superb at crimping that one size connector. but may not be much use for anything else.

From my experience crimping a dozen conventional terminals, the $25 crimpers work well. I haven't tried them on MC4 connectors.

The challenge with $25 crimpers is being sure that you have a tool that fits the connector. This is where you're going to need to be compulsive in comparing drawings and dimensions. First decide which exact connector you plan to buy. Then get the drawing for that connector and find out the diameter of the uncrimped barrel. Match that to the tools available.

Or buy pre-assembled cables.