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Old 26-03-2018, 04:41   #1
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Bigger cable for MC4 connector?

The MC4 connector specs I've seen seem to be limited to 10 AWG or 6 mm2 wire. Is it possible/does it make sense to fit a 10mm2 (~ 7 AWG, quite common in Europe) cable? I want to minimize losses as much as possible and also try to avoid using all kind of junction boxes exposed to the elements.

My actual panels (450Wp total) could probably do more or less fine with the standard 6 mm2 but I'd prefer to do the wiring as future-proof as possible and leave some room for upgrades.
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Old 26-03-2018, 05:10   #2
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Re: Bigger cable for MC4 connector?

A bit of a basic answer but...If you are wiring your panels in series, you don't need the bigger cable as the amperage does not increase.

If you're wiring your panels in parallel, the 10awg will suffice until it goes through the bulkhead or whatever where the various 10awg's can meet up to a larger cable which can take it to the controllers/batteries.
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Old 26-03-2018, 05:53   #3
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Re: Bigger cable for MC4 connector?

The plan is to go 2series 3parallel, and joining the cables on deck with MC4 Y-connectors. After these I expect 10A current now, maybe 20A in the future (to mitigate shading issues, I am reluctant to build very long series groups). Anyway, I didn't want to worry much about losses, just wanted to buy a one size bigger cable - if possible - to stay on the safe side.
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Old 26-03-2018, 06:01   #4
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Re: Bigger cable for MC4 connector?

This is probably not what you want to do, but I used one of those weatherproof plastic boxes with the O-ring seal on the cover. I put a terminal strip in there then you can use whatever size wires you care to. The final installation was underneath the panel to keep it out of the direct weather
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Old 26-03-2018, 06:47   #5
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Re: Bigger cable for MC4 connector?

MC4 is commonly used ​with 2.5mm2 (14), 4mm2 (12), 6mm2 (10).

You can get #8 but it's rare, the die's expensive, and that's the biggest.
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Old 26-03-2018, 06:48   #6
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Re: Bigger cable for MC4 connector?

Quote:
Originally Posted by motion30 View Post
This is probably not what you want to do, but I used one of those weatherproof plastic boxes with the O-ring seal on the cover. I put a terminal strip in there then you can use whatever size wires you care to. The final installation was underneath the panel to keep it out of the direct weather
My solution too, only the junction is below deck as the panel came with 5m long wire. First thing I did was cut off those MC4 connectors because they are a pain to thread through the boat and waterproof deck seals.

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Old 26-03-2018, 06:49   #7
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Re: Bigger cable for MC4 connector?

call genuinedealz see if they can make custom for you
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Old 26-03-2018, 07:03   #8
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Re: Bigger cable for MC4 connector?

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call genuinedealz see if they can make custom for you
I think the boat is on the West Coast so costs could be a problem, post 105 refers:

MPPT vs PWM cotrollers?
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Old 26-03-2018, 07:11   #9
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Re: Bigger cable for MC4 connector?

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I think the boat is on the West Coast so costs could be a problem, post 105 refers:

MPPT vs PWM cotrollers?
Exactly . And I don't intend to create a bigger problem as it actually is. If there is no straightforward solution (soldering the contacts instead of crimping, etc), I'll just go with the 6 mm2 wire, full stop. I'll give a second thought to a ready-made combiner box, maybe it's not a bad idea if I want to install a Schottky between the parallel groups.
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Old 26-03-2018, 08:10   #10
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Re: Bigger cable for MC4 connector?

Use the 10awg above deck, then switch to larger for the run below deck. The losses caused by the smaller wire only apply to its actual length, which is short.
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Old 26-03-2018, 08:15   #11
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Re: Bigger cable for MC4 connector?

What is the output voltage of each of your series panels? What is the output current of each of your series panels and the current downstream of the combining wye.? And, finally, what is the circuit length from panels to the batteries, broken down into the series portion and the parallel section?

With this info, you can enter voltage drop tables or use a wire sizer app and adjust the AWG/mm^2 wire size until you attain a reasonable voltage drop.
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Old 26-03-2018, 08:27   #12
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Re: Bigger cable for MC4 connector?

I soldered 10mm2 cable in MC4 connectors. It can be done, is a bit bulky but works. I did it for the same reason as you. Was not really necessary but if it is possible, why not. The other solution of course is to just cut off the connector and do a watertight crimp with heated glue.
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Old 26-03-2018, 09:33   #13
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Re: Bigger cable for MC4 connector?

I used 8 awg from Windy Nation.
https://www.amazon.com/WindyNation-E...w%2F+mc4&psc=1
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Old 26-03-2018, 10:24   #14
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Re: Bigger cable for MC4 connector?

For 10 gauge wire
Code:
% losses = length in ft * current / voltage / 10
So with 20 ft of wire and 100 watt panel (8 amps) your loss is only 1% so 99 watts instead of 100. You are wasting money on 8 gauge wire.

You would be better off using mppt, larger panels, more efficient batteries, more efficient devices etc.. than worrying about wire size here. If you upgrade to 20 amps, and have 2% losses, it's not going to matter much with all that power.

I use 14 gauge wire for 150 watts and twist all the connections (inefficient when corroded) and I still have plenty of power.
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Old 26-03-2018, 10:30   #15
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Re: Bigger cable for MC4 connector?

Unlimited solar and Windynation both sell 8 AWG solar extension cable on Amazon in lengths from 3' to 150' .

https://www.amazon.com/WindyNation-E...c4+cable&psc=1
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