Author Topic: MC4 connector ratings (brand differences)  (Read 1463 times)

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Offline jack11

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MC4 connector ratings (brand differences)
« on: May 06, 2013, 12:25:49 PM »
I believe the original mc4 connectors have ratings of 600Vdc, and the amperage dependent on the cross-section of the wire used, up to some max value.

In my pool of mc4 connectors I have some original mc4 brand, plus about 3 other knockoff brands.

I've notices slight differences in the geometry between these brands, the one that has me concerned is the male-female metallic parts overlap (the area thru which the actual connection is made). I measured these overlaps as these different brands are mixed, and the difference may be as large as 2 mm of overlap for the brands I have, possibly more for other brands.

So the question is: what's the minimum length of metallic parts overlap to maintain the mc4 ratings, especially the amperage rating? I've called a few places but haven't been able to get a clear answer.

Offline oztules

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Re: MC4 connector ratings (brand differences)
« Reply #1 on: May 06, 2013, 03:26:31 PM »
I would not be too carried away with overlap.
If you think about it, the current carrying of the plug is designated by the cross sectional area of the tubes that fit into each other on connection. The cross section is very small.

To carry that current from one plug to the next requires the same cross section area as overlap area...... so very little overlap is required for current transfer from plug to plug with the same losses.

The really critical thing is the mating of the two surfaces. Provided they provide a good connection, the problems are minimal. It is the integrity of this intersection, not the surface area so much that is the real problem. If it fits tight, it should be right... regardless almost of the overlap. Loose connection will kill it pronto, regardless of how much overlap you have.

The boffins may/may not have some regulation about it, but it is all academic if the thing is loose.



...............oztules
Flinders Island...... Australia

Offline jack11

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Re: MC4 connector ratings (brand differences)
« Reply #2 on: May 07, 2013, 02:59:46 PM »
the cross-section makes sense. I guess, ideally if one could make a perfect butt-to-butt connection between two tubes of equal diameter, with no overlap at all, then the rating should be maintained.

But, in the case of mc4 the tubes are not equal diameter. And I think the male post of mc4 is tapered/rounded at the end to ensure self-alignment when connecting (the shape and length of taper varies between different brands). So, to have a snug fit there must be some overlap to at least exceed the tapered length plus additional small area equal to the cross-section.

All this is difficult to measure because it's hidden deep in plastic, and I have a feel that I may be operating on the hairy edge when I mix different brands. But I keep checking these connectors, and haven't seen any arcing or heating problems yet.