Panel to Solar Controller Wire Size

Some reason here lately I keep getting double posts - have no idea why this is happening haha...

Double clicks I guess

Roy Ken

I ordered my very flexible ANCOR Marine grade 4AWG cable from ebay stores sources for around $50 for a 25-foot spool. You can also use ANCOR Ring Terminals...





Use adhesive-lined HD heat shrink tubing to cover the ends as shown


I used this 8-ton hand crimper to install the ring terminals $69 AMAZON


Roy Ken

You did - probably - right by going for 45A charger instead of 20A. This is 600W array that you may potentially have. If your roof allows more panels, don't do it wrong now by sizing your wiring to 300W only because you are buying 300W today.

450/130 x8.2= 28a but less when flat.

15 ft pos and neg, #8 about 1/2 a volt drop

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=12&phase=dc&noofconductor=1&distance=15&distanceunit=feet&amperes=28&x=74&y=6

With 12v PWM the voltage drop panel to controller is less critical than from controller to battery. My old ASC manual says 1/2 volt array to controller is ok and 1/4 volt for controller to battery.

IMO #8 is the right amount. In your over-all set-up you have already decided not to try to squeeze the last amp out of it, just be reasonable and leave it at that. So it would be strange to worry about a milli amp or two by using fatter wire than # 8 for this part of the set-up. I would agree with fat wire from controller to battery, epcecially if you can share with the inverter's wires for part of that path for instance.

smkettner wrote:
GD calculator says you lose .8 volts with #10 and .5 volts with #8 with 25 amps flowing. #10 is minimum for ampacity IMO.

Say they are 18v Pmax panels you will still have 17+ volts hitting the controller so I would call it good. #6 would be killing it but could work after the controller if using the same coil of wire.

This is good feedback.

A better analysis would involve knowing the panel specs, each panel to combiner wire length and then the actual length combiner to controller and controller to batteries.

Hi Mena,
I generally recommend designing a system around 2% (or less) voltage drop…
Taking your 450W figure (I used 35A), and assuming 40 feet of wire (20 feet each of + and - conductors) you will need to 6ga wire to stay at 2%. 4ga would be slightly better, but IMHO would not worth the extra cost. With the 6ga wire you can safely select a fuse in the neighborhood of 75-80A to keep losses low and still have a good margin of safety.
In terms of ampacity alone, you would be fine going as small as 10 or even 12ga… but personally I'd spend the extra $$$ to keep the voltage drop in the 2% range.
Cheers
-Mark

GD calculator says you lose .8 volts with #10 and .5 volts with #8 with 25 amps flowing. #10 is minimum for ampacity IMO.

Say they are 18v Pmax panels you will still have 17+ volts hitting the controller so I would call it good. #6 would be killing it but could work after the controller if using the same coil of wire.