what amp cable?

Juggenaut · Veteran Member

what amp cable?

oldgrey52 · Member

Juggernaut - 6B&S will be more than ample.

Aus-Kiwi · Guru

Yep. Cable and plugs can be bought at Battery world or Jaycar . Just Multy plug them together if using Multy panels . The wire size is around 6mm . Easy plug and play system . Water proof too .

Juggenaut · Veteran Member

thanks oldgrey for the imfo

PeterD · Guru

what amp cable?

A little bit of info for you. Never purchase cable on the basis of its current carrying ability. The current carrying capacity rating of a cable is the current that will cause it to heat up and melt the insulation. If your cable is heating up it means that you have a significant voltage drop along it. You should always select cable by the cross section size (or in other words how much copper there is in it.) The international sizing of cable is in in square millimetres, abbreviated as mm2. There are tables and online programmes for you to work out what size you need. Try this calculator.

Using the above link - your 140 W panel will provide around 8.5 A maximum (140 / 17 = 8.235.) A 5% voltage drop is acceptable for solar panels. Assuming you need 4 metres of cable (8 m there and back.) If you put those figures into the calculator it tells you that you need 6 mm2 or 10 AWG cable. As Oldgrey said, 6 B&S (13.25 mm2) is more than adequate but the 6 mm (4.85 mm2) auto cable that Kiwi suggested is a bit on the light side.

Aus-Kiwi · Guru

6mm square . As said .. Which is pretty much the size of cable that comes made up in solar panel and wiring from commercial retailers . . Btw it's to charge the battery .. Not that it's designed to take the total load as per battery cable . Note the size of wire off a 60amp charger ? It's defenatly not 100mm cable !!.

-- Edited by Aus-Kiwi on Tuesday 14th of June 2016 06:22:00 PM

Juggenaut · Veteran Member

thanks Pete & Auskiwi both for your infomation.

Hylife · Guru

Juggenaut wrote:
i am mounting a 140watt solar panel to the roof of my pop top van. what size cable would be best to run from the panel to the regulator?

Depends where the regulator is positioned (on the back of the panel or next to the battery)?, and, is there any other panels?

Longer wire runs require bigger cross-section of copper.
Higher amps requires bigger cross-section of copper.

A single 140 watt panel will only put out about 6 to 7 amps in full midday summer sun at approx. 30 degrees south of the equator. Closer to the equator or the poles provide less power due to the tilt of the earth on its axis.
Your MPPT reg will up the voltage when its output drops to maintain the right charging voltage but even the best panels only run at about 70% efficiency with full midday sun.
140W divided by 14.4volts times 0.7 = 6.8amps (full sun)
Mid afternoon unless you angle the panels to be 90degrees to the sun expect 45% efficiency = 4.3 amps

Now if that reg is on the back of the panel, thin 14 or 12 AWG will do fine at such a short distance.

If that reg is in the van boot and you have other panels hooked together with this one then you need to work out the maximum current output at midday and the length of the run of wire before we can give you an accurate answer.

Aus-Kiwi · Guru

Reg is best near battery . So higher voltage to reg negates large cable size . Besides the solar panel type regs seems to be of low quality ..

oldtrack123 · Guru

Hi
As others have posted current rating is rarely the problem with 12V wiring
The voltage drop when under full load current is usually the main consideration
!2v equipment usually requires a full 12V to operate efficiently
That means the cable length & the max current it will be required to carry determines the cables CROSS SECTIONAL AREA of ACTUAL COPPER!!

PeterD · Guru

I used to say "if you are concerned with the current carrying capacity of your cable when running cables around a caravan then the wiring you intend to use is too light." I have ceased using that as it tended to confused people. However what has been said above supports my message.

Aus-Kiwi · Guru

Cables connectors from solar panels are either 4 or 6mm sq . The connectors on most regulaters Canot take much bigger size wire anyway ., On my Pro Star Atleast ., on the BATTERY and load side the cables to inverter are large , guessing Atleast 35mm sq . About the size of your little finger . From battery . It's best to have seperate circuits for each appliance . Not like 240v with multiple power points .. Speaker wire size should NEVER be used in anything other than LED lights etc .