Solar Power - Cable size from MPPT to Battery Bank?

[DCH]

Hi.

 

Could someone please tell me what size cable I should be using from my MPPT controller to my 12v battery bank with 3x100W solar panels connected in series? Distance from MPPT to batteries is 1.50mts.

 

Thanks for your attention.

 

DCH

Edited July 19, 2014 by DCH

[Nickhlx]

It matters not what is on the input side to the MPPT, but if it potentially can put 300 watts ( 25 amps) or so in to the battery bank, you should size based on that

 

For that short distance 4mm2 should be fine, but I would use 6mm2.. and enjoy the fractionally less loss..

 

What cable size has been used from the panels to the MPPT, and what is the length of the run ? Being in series, the voltages of the panels will add, and the current will probably be no more than around 8 amps peak, but this run from the panels to the MPPT will likely be somewhat longer, than from the MPPT to the battery bank.

 

Nick

Edited July 19, 2014 by Nickhlx

[leeco]

6mm2 mate

[b0atman]

same set up as you slightly longer 2m run with 6mm cable lose 0.2 volts so am upgrading to 10 mm sq

as the actress said to the bishop every little helps

[Grace and Favour]

6mm² would be the optimum in terms of minimising voltage loss, and within the practical parameters of finding MC connectors (it's difficult to find connectors that will take a larger diameter cable)

 

Please make sure you use proper solar cable, (which is UV resistant!)

[matty40s]

6mm² would be the optimum in terms of minimising voltage loss, and within the practical parameters of finding MC connectors (it's difficult to find connectors that will take a larger diameter cable)

 

Please make sure you use proper solar cable, (which is UV resistant!)

cough, read the OP!!! , controller to battery doesn't need MC connectors - or UV resistant cable.

 

I used to install with 6mm2 , however, with most customers seeming to surmise that they may add to the array at a future date, now use 10mm2 from controller to batteries, with a fuse holder capable of taking larger capacity fuses.

[bottle]

or

 

as big as the terminals of the MPPT will take.

[DCH]

Thanks to everyone for your help. I'm glad I checked because someone told me I could get away with 2.5mm.

[smileypete]

If the controller uses screw terminals it may be well worth putting 'bootlace ferrules' on the bare ends of the cable. (try Ebay, eleccy distributors for supply)

 

In the US there are a number of cases of burnt MPPTs which may well have been down to loose screw terminals:

 

 

http://www.kg4cyx.net/xantrex-xw-mppt-60-150-squeezing-60-amps-through-a-toothpick/

 

cheers, Pete.

~smpt~

Edited July 21, 2014 by smileypete