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The question seems to always come up and it is so important that we get it right. So let's try to keep this great chart near the top at all times so that it is easy to find for anyone just getting starting.
For example: If you have 3 solar panels rated at 6 amps each, mounted 30 feet from the Charge Controller, then you would move down the chart to 18 amps (3 panels * 6 amps), and across to 32.5 (closest to 30), and then up the chart to #4. You would need at least #4 gauge wire (awg) to move 18 amps 30 feet with a minimum voltage drop of 3% or less, an acceptable loss. If you can't find the exact numbers, choose either a larger gauge wire (smaller number) or select a distance longer than your actual distance.
Wire chart for connecting 12 Volt solar panels to the Charge Controller
This chart shows wire distances for a 3% voltage drop or less. These distances are calculated for a 12 volt system. Multiply distances by 2 for a 24 volt system. Multiply distances by 4 for a 48 volt system.
NOTE : This chart is an approximate distance reference and is a little conservative.
Amps #12 #10 #8 #6 #4 #3 #2 #1 #1/0 #2/0
4 22.7 36.3 57.8 91.6 146 184 232 292 369 465 feet
6 15.2 24.2 38.6 61.1 97.4 122 155 195 246 310
8 11.4 18.2 28.9 45.8 73.1 91.8 116 146 184 233
10 9.1 14.5 23.1 36.7 58.4 73.5 92.8 117 148 186
12 7.6 12.1 19.3 30.6 48.7 61.2 77.3 97.4 123 155
14 6.5 10.4 16.5 26.2 41.7 52.5 66.3 83.5 105 133
16 5.7 9.1 14.5 22.9 36.5 45.9 58.0 73.0 92.0 116
18 5.1 8.1 12.9 20.4 32.5 40.8 51.6 64.9 81.9 103
20 4.6 7.3 11.6 18.3 29.2 36.7 46.4 58.4 73.8 93.1
25 3.6 5.8 9.3 14.7 23.4 29.4 37.1 46.8 59.1 74.5
30 3.1 4.8 7.7 12.2 19.5 24.5 30.9 38.9 49.2 62.1
35 2.6 4.2 6.6 10.5 16.7 20.9 26.5 33.4 42.2 53.2
40 2.3 3.6 5.8 9.2 14.6 18.4 23.2 29.2 36.9 46.5
Posted courtesy of Free Sun Power
That's a great chart, Ray...in the beginning, I was flying by the seat of my pants and said..."Hmmm, wire gauge...ahhhh, 12 gauge? Sure, cheaper then 10 gauge"...well it turns out at 15 feet, I got lucky for 2 kits, but now with 3 kits + 1 single, I really should have gone the extra bucks and went to 10 gauge....the newbie has severelly rubbed off of me and the picture is perfectly clear now....at some point, maybe this summer, if I can find it, I'll probably go to 8 gauge, at least for the longest, continuous part of the run, or 10, which is readily available, but that brings another question to mind, and I've brought it up before, just don't remember any answer...the wind turbine (50 watts) has about 3 feet of rather small gauge wire from the actual mill motor, maybe 18/20 gauge (this is because the wires come out of the turbine inside of the mounting pole and with the constant direction changes, it needs to be thin so as not to bind the turbines movement), connects to a voltage doubler board, uping voltage from 12 v to 24 v, then down some 15 feet on 16 gauge wire to the merge point where it merges with the 12 gauge line...if I were to change that 16 gauge to 10 or 12 gauge, would there be any significant increase in amps? The wind mill voltage is good at the present config at the switch, I just think I'm loosing amps with the thin wire (20 to 16 to 12)...what you think? Would it make a difference or is the run just too short (maybe total length to the merge, 25 feet)?
I don't have much practical experience with wiring turbines bit at a glance I think you are fine with your current set up. I can see where if we were talking 12 volt the whole length that the 16 to 12 section of that 20 to 16 to 12 could be a problem. But your not, we are talking 24 volt at that point and if you double your lengths as the chart says to it looks like you are fine.
So, my vote is that you would gain nothing by upping the gauge. Remember, you gain nothing by increasing the gauge unless you are undersized.
Great post Bill K, I think we will start a Wind Turbine category since everyone of us needs to be thinking about adding these small wind turbines to supplement our solar.
I was wondering what TTT meant!
It's internet forum lingo for "To The Top". We use it instead of making a comment to bring it to the top of the conversations.
Hi Dave, I guess when the power lost over your current wire run becomes unacceptable or insulation starts smoking at which time its too late? <grin>
Seriously, you have several potential options. In your "situation", (he says green with jealousy), I would probably divide the panels into two arrays of 12 panels each and run two 8 gauge wire pairs to my controller, of course if the controller is set up to handle a 24 volt input, (its actually much higher), I could re-connect the panels into series/parallel "pairs" and stick with 1 run of 8 gauge at 24 volts - reducing current by jacking up the voltage while providing the same power. (I'm judging 8 gauge as *my* absolute minimum to carry that many amps for 70 ft and consider that borderline, but probably "OK", your mileage may vary there in San Antone).
Ray's chart is trying to keep the voltage loss along the transmission line (wire pair) down to 3% or less - that doesn't mean where things will start to smoke - I like the idea of getting more power to my batteries and wire is still cheaper than what you had to spend to generate/store all of that electrical power to begin with.
That has got to be one *very* nice problem to have Dave! I am working toward winding up with half as much as you already have. ;-) -=dave=-
Okay Dave I really appreciate your input but what about this...
Each panel puts out lets say 1Amp so that is 8Amps into ea. junction box. To that point wouldn't everything be good? Wouldn't I ony need the heavier wire from those junction boxes to the charge controller? That way the larger wire would only be about 30 or 40ft. to the charge controller.
Now what comes to mind is if I have an item that pulls many amps upon start up but that would be pulled from the batteries for just a second not from the panels.
I'm thinking here.
OK Dave, basic misunderstanding here. When you originally said "I would need about 70 ft of wire" I thought you were talking about 70 ft. being the length to wire to go from the junction box to your controller, or a 70 ft run (obviously Ray thought so too) - upon re-reading it, I'd be willing to bet that distance is somewhere around 35 feet and you were counting the total to run one positive and one negative, or the total amount of wire you would have to buy. That, (30 to 40 ft.), makes all the difference in the world if that is the case.
I also took time to read all of your posts in the forum and now have a little better idea of what "I think" you want to do. Essentially dividing your 24 panels into 3 arrays of 8 panels each. IF you ran a wire pair from each of the 3 junction boxes to the controller, you would be pushing somewhere around 8 amps at 12 v and should use 8 gauge wire for each of the wire pairs - joining them all at the controller. Yeah, that is 6 wires, but it is a good way to divide things up and still stay below a 3 volt loss due to the inherent resistance in the wire itself. Man I hope that helps.
Smarter folks than me have said that by the time you have put out the money and labor to build a system "wire is no time to try to go on the cheap".