Panel cable.

[paulca]

My little panel came with fairly light gauge wire on it.  Not only that it has about 3 meters of the stuff.  My charge controller is within 1 meter of the panel.

I noticed today, with the panel producing 2A that the PV cable is a little warm.  This could be voltage drop along it or it could just be the heat from the panel soaking along the cooper.

Is it best practice to cut the cables to the minimum length required, accepting that I might need to resolder new wires if I move the panel, or does it really matter?

In fact maybe I should pop the cover off the junction box on the panel and solder a shorted length of much heavier cable on there.

[CM800]

Hello Paulca,

I highly doubt that it's getting warm from heat travelling along the copper core...

Depending on how much you paid for the panel, it could likely be they have went with the bare minimum for the cable thickness.

If you can check the wire gauge, I would suggest doing so, and changing it if you care about it.

You can never go wrong shortening a cable if you won't ever need it longer.

[Richard Crowley]

It is also possible that it is some sort of cheap cable that isn't really copper. Copper-plated steel has often been seen in low-end products from asia.  If the wire is getting warm, certainly it would be better to replace it with heavier, real-copper wiring.

[paulca]

Yea.  I think I should. 

The panel never seems to get over 15V, but it's MPP is 17V.  Could I be dropping a whole 2V in those cheap cables I wonder.

I have some good 18 AWG tinned copper wire that ought to do the job, over a 1 meter length.

[fourtytwo42]

Yea.  I think I should. 

The panel never seems to get over 15V, but it's MPP is 17V.  Could I be dropping a whole 2V in those cheap cables I wonder.

I have some good 18 AWG tinned copper wire that ought to do the job, over a 1 meter length.

Umm insulation ?
Also what is ISC of your panel (should be <= 10Amps) ?

[paulca]

Yea, it's either the cable or more like the window glass, or a combination of both.

ISC is 2.93A.  MPP 18.32V

It doesn't carry a brand, just says "Solar Module Type 050M...." and the datasheet summary, on the back.

It a generic 36 cell 50W panel.  Cost me £54.

[SeanB]

Replace the cable, using some 1mm mains rated cable, simply because the mains rated cable is easy to get in stores either as precut cable or simply by buying a standard 2m mains extension and cutting the plug and socket ends off it. Then the rear of the panel the connection box is easy to open and replace the existing cable using the new one, and feed it through the same rubber grommet, which will be a lot tighter than the original, and either the cable has screw connections inside or solder connections. You just use the brown and the blue conductors, and ignore the green yellow PE each side.

Makes a big difference in those panels, though I used 1m of the cable and then went to 4mm copper wire to run down, as I had a long way to go. On a good sunny day like today I get nearly the full 50W out of the panel.

[fourtytwo42]

Replace the cable, using some 1mm mains rated cable, simply because the mains rated cable is easy to get in stores either as precut cable or simply by buying a standard 2m mains extension and cutting the plug and socket ends off it. Then the rear of the panel the connection box is easy to open and replace the existing cable using the new one, and feed it through the same rubber grommet, which will be a lot tighter than the original, and either the cable has screw connections inside or solder connections. You just use the brown and the blue conductors, and ignore the green yellow PE each side.

Makes a big difference in those panels, though I used 1m of the cable and then went to 4mm copper wire to run down, as I had a long way to go. On a good sunny day like today I get nearly the full 50W out of the panel.

Just one small thing to add, you want the stranded flexible cable NOT the solid stuff with a bare copper earth.

[paulca]

The solid core installation wiring doesn't bend well.  I think I can get twin flex stuff, but I don't believe it's as high gauge.  The 3 core stuff comes in 13A and even higher here, but the twin core seems to be rated for 6A.  Surely 6A rated mains wire is enough to avoid voltage drop for 2.7A?

[fourtytwo42]

It should in theory be adiquite especially as you only require a meter BUT in the modern world of shaving every penny off of everything it might be rather thinner than I would expect, you have to remember that it is designed to not drop to much voltage in a 240V circuit, so that could easily be several volts I have seen some of that stuff that looks more like 2 or 3 amps to me, but then I am to old and remember when things were made properly hahaha Unfortunatly going up to 13A you can only get 3-core but hey reduce the voltage drop even more by paralelling the earth with one of the other cores. Only you have the panel so try go for the biggest you think you can get in its terminal box. If its soldered be sure to use a heavy hot iron so you can be very fast to avoid damaging anything else lurking in there

[IanMacdonald]

Beware of cheap wire which is actually copper plated iron. Has a much higher resistance than you would expect.

That said, solar panels are more or less constant current devices so unless you have an optimizing controller which takes advantage of the best terminal voltage, losing a volt or two will not make any difference to the rate of charge.

[NiHaoMike]

In the US, a cheap source I have found for known good stranded 16AWG wire are extension cords. Especially when they're on sale and the connectors are a bonus.