Solar panel cable
Submitted: Thursday, Aug 20, 2009 at 13:24
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Robert HL (SEQ)(aka zuksctr)
Hi all,what would the minimum size cable used for a 100w solar panel over say 5-10 mtrs?
Thanks,
Bob.
Reply By: ABR - SIDEWINDER - Thursday, Aug 20, 2009 at 16:02
Thursday, Aug 20, 2009 at 16:02
Hi Bob
I would use 6mm2 if possible. You can use standard 6mm auto twin core which is 4.58mm2 and has the outer sheath. I don't like the twin flex cable without the extra protection.
4mm as mentioned may do 5m but not recommended for 10m.
If the solar controller is mounted on the panel then use the heavy cable to prevent voltage drop.
Our GP100W Bi-Fold is supplied with 6mm2 twin core sheathed cable.
Regards
Derek from ABR
AnswerID:
379697
Follow Up By: Richard & Leonie - Thursday, Aug 20, 2009 at 21:52
Thursday, Aug 20, 2009 at 21:52
Derek, I understand there are two types of 6mm*2 cable. Which is best? Could you comment on the statement lower down that the solar controllers HAVE to be at the battery end of the cable.
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647145
Follow Up By: ABR - SIDEWINDER - Thursday, Aug 20, 2009 at 22:10
Thursday, Aug 20, 2009 at 22:10
6mm2 it would be tinned or plain copper.
Try use tinned (See picture) You will know it is 6mm2 if it is a tight fit in the yellow lugs. (Tinned is silver in colour) The picture in reply 4 below looks like 6mm automotive which is 4.5mm2, don't be confused by this as many people are.
Solar controller, this would depend on how portable you want to be. Sure the controller is better on the battery end but all portable panels that are used on multiple vehicles etc need the controller fixed to the panel. Lying loose would be looking for a potential fault in the system. Using good cable will eliminate this problem anyway and once the battery is charged and the controller starts to regulate the charge it will make no difference.
Regards
Derek from ABR
FollowupID:
647154
Reply By: Mandrake - Thursday, Aug 20, 2009 at 20:24
Thursday, Aug 20, 2009 at 20:24
Just being curious here - Voltage drop over a few metres of cable ..
If the panel is kicking out 21 volts or 18 volts is it really all that important
if you drop 1 or .5 volts ? you're still delivering 17 volts to the regulator
and that is enough to charge an AGM surely ??
Or am I missing something ??
Mandrake - still 2 days away and on final count-down ..
AnswerID:
379742
Follow Up By: oldtrack123 - Thursday, Aug 20, 2009 at 21:55
Thursday, Aug 20, 2009 at 21:55
Mandrake replied:
Just being curious here - Voltage drop over a few metres of cable .
If the panel is kicking out 21 volts or 18 volts is it really all that important
if you drop 1 or .5 volts ? you're still delivering 17 volts to the regulator
and that is enough to charge an AGM surely ??
Or am I missing something ??
HI
If the reg is close to battery not so important.
Reg responds to voltage it sees @ it's terminals, <0.2volts not much problem but if higher could affect SOC of batts
FollowupID:
647148
Reply By:- Friday, Aug 21, 2009 at 16:28
Friday, Aug 21, 2009 at 16:28
Some more numbers...
Ordinary 2.5 mm square flexible 'extension cord' wire offers a resistance of around 7 mOhm per metre.
Your max peak current from your 100W panel is around 7 A.
And for the most part of the day, the current is a lot less.
Nevertheless, lets do the numbers for 7 A:
you're looking at a voltage drop of 50 mV per metre.
If your total wire run was 10 metres, then you'd have a drop of .50 V or around 3.5 W power loss in your wire.
Using a 4.5 mm square wire, youd get a drop of about 28 mV per metre, or a power loss of around 2 W per 10 metre run.
The difference is a mere 1.5 W between these two wire types.
Solar panel wattage costs about 7 bucks, so we're looking at a $10 loss inferred by the lighter gauge wire - what's the price difference between an extension cord wire (Crazy Clarks?) and a '6 mm' (Super Cheap?) auto wire for this run of 10 metres?
Price figures anyone?
Best, mr.batteryvalue
AnswerID:
379886