Cable requirements for solr panels

[pcatterall]

Panels arrived today. I got 2x Lensun 40watt panels ( £139) which I will mount initially on the pushpit.
Quallity looks ok and the junction box seems up to the job. In the end I went for a 10 amp PWT regulator.
I did order some connector cable for these panels with the intention of buying more if the stuf was OK. In fact the cable looks like overkill to me being seperate pos and neg leads of around 1mm section and very stiff. Possibly the stuff is used where there are multiple arrays carrying (together) a large current. My plan is just to link these two panels together in parallel and then run the lead to the regulator and the batteries.
Have I missed some important point and do I really need cable of this size fro these two panels?
Your advice as always most appreciated.

 

[ex-Gladys]

With low voltage systems, the longer the cable run, the more voltage drop and therefore the less effective the charge from your panels. Long story short, the thicker the copper the better...

Here for example is a calculator... http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

6 amps over 10 metres requires 10sq mm cable for a voltage drop of <2%

 

[pcatterall]

Larry, Thanks, thats an excellent little calculator. Suprising result though!! I can probably get away with 6mm twin core stuff for the length and anticipated amps. I suppose my thinking was clouded where equipment is happy to work ok with a bit of voltage drop. Also I have seen a few set ups on various yachts but didnt notice such large cable sizes. Calculator stored in favourites!

 

[VicMallows]

I think you are worrying too much with 2 x 40w (same as I have). When you have anything like the likely 6A maximum (for a few hours a day in summer!) the panel voltage will be high enough for a slight voltage drop to be insignificant. The rest of the time the charge current -and hence voltage drop due to cable resistance - will be much lower and unlikely to be of any significance,

I would put most effort into ensuring the panels have the clearest, un-obscured, exposure to the sun. That's the hard part

Vic

 

[pcatterall]

One additional question arising.
Looking on the above site for 6mm twin core and am not certain if the figure refers to the section of each of the 2 cables or to both of them together.
Can anyone advise?
Thanks also Vic for your comment,perhaps I could drop a size. I did a test with one of the panels today and certainly saw a great difference when the panel was aligned at 90 degrees to the low sun..
I'm trying to work out the best way to construct an omni directional mounting.

 

[VicS]

Looking on the above site for 6mm twin core and am not certain if the figure refers to the section of each of the 2 cables or to both of them together.

6mm² is the cross sectional area of each conductor.

 

[ex-Gladys]

I have two Solara semi flex panels mounted on Gladys Wheelhouse supplied by Barden, they recommended 5 sq.mm. My one season of use has convinced me it was one of the best things I've done. Not charged the domestic bank from the mains all season. Mainly weekend sailing apart from a week aboard in Chatham, and constant use of a compressor coolbox, very impressed with the performance.

 

[simonfraser]

i have one on each side of the cabin, swinging mooring, 90 to the winter sun, works much better than horizontal on the deck.
can't see out of most of the side windows though, at least the heater works