Distance and wire size

[brushstroker]

I have 3canadian solar 235w, 29.8 voc, 7.9 imp panels
And id like to run them close to 100ft away from my renogy tracer 40 mppt charge controller. Can I do it with 4 guage copper wire that I already have?

[brushstroker]

Sorry, It's going into a 12v system

[Sunking]

Not going to work, and will never happen. So why bother to answer your question?


With 705 watts of panel into a 12 volt battery requires a 60 amp controller there genius. . You only have a 40 amp controller. That ggives you 4. choices:

1. Your best option give up and forget about it before you loose more money.
2. Use 24 Volt Battery
3. Buy a 60 Amp Controller
4. Loose a panel.

Take your pick, then vcome back with questions.

If you had a 60 amp controller it would take 2/0 cable. 220 feet of 2/0 will set you back $8/ft or around $1600.
FWIW 12 volt battery is for boys, toys, and RV's Otherwise of no use.

[brushstroker]

So if I dropped a panel for now until I get my hands on some different stuff what would be the max distance I could go with that?

[SunEagle]

The only way you can use those panels and that 40A MPPT is to get rid of one panel. And that #4 wire is way too small for that 100 foot run so you would need to move them a lot closer to the CC.

As Sunking states. You need a bigger MPPT and bigger wire or less panels and shorter distance.

Although you could use a 30Amp PWM CC and wire those panels in parallel but then you turn 700 watts into 300 watts which would be a big waste of money.

[brushstroker]

I understand all that I have a small system with 2 panels running into my 40amp cc right now. But there directly on my shed where they don't get enough sun. My question is
If I keep it the way it is with only 2 panels hooked up ( going 24v right now is not readable.) What's the furthest I can go with the 300 ft of free 4guage wire that I have? I understand that my controller is too small to use all 3 of them I actually have a 4th but need to get it to my house yet.

[SunEagle]

I understand all that I have a small system with 2 panels running into my 40amp cc right now. But there directly on my shed where they don't get enough sun. My question is
If I keep it the way it is with only 2 panels hooked up ( going 24v right now is not readable.) What's the furthest I can go with the 300 ft of free 4guage wire that I have? I understand that my controller is too small to use all 3 of them I actually have a 4th but need to get it to my house yet.

Ok I went back and read your post again. The long distance is between your panels & CC and not your CC & battery so....

You still can't use more than 2 panels but based on my new calculations (which could be wrong) with an output voltage of ~ 60VDC (that is 2 panels wired in series) and a current of 7.9 amps the one way distance for a #4 wire that meets a 2% VD is ~ 130 feet. So 100feet might be ok. But I want others to check my math because I have been know to move a decimal place now and again.

[brushstroker]

So when I can afford to go 24v and add my other 2 panels can I have all 4 at 100 ft at 24v ?

[SunEagle]

So when I can afford to go 24v and add my other 2 panels can I have all 4 at 100 ft at 24v ?

By calculation you should be able to use 960 watts and that 40amp MPPT CC to charge a 24volt battery bank. That should allow you to use 4 of those 235 watt panels. You have to check to see what the max DC input voltage is to determine how to wire the panels. I doubt you can wire them all in series but probably 2 sets in parallel of 2 in series.

Now with a total of 4 panels wired (2 x 2) the voltage stays at ~ 60VDC but your amps go up to ~ 16 so now the max one way distance for a #4 wire goes down to ~ 70 feet. Again that is based on my calculations and it could be wrong.

[cabindave]

Brushstroker,
As stated above, you have a couple options. Run two of your panels if at 12v, or go with 24v and run all 3. If the long wire run is between the panels and the charge controller 100ft at 4 guage is no problem in your case. I believe the 40A renogy (tracer) specifies 800w as the max in the manual. Take a look at the manual. That should also help you to fuse it correctly. Make sure to use DC rated fuses.
If you have at least two batteries, have you considered running a 24v system, and then just getting a 24v to 12v converter? They are cheap.

If you run 3 panels (the 24v system), you should be able to make them all one series as I believe that controller has a 100 volt rating. SunEagle may indeed be correct about it handling more than 800 watts. The documentation just specs the max as 800 watts at 24 volts.

[Logan5]

You are stuck inside a 12 volt box way of thinking. Stop that. If you run a 24 volt system with a quality MPPT CC, you can run 100 volts that 125 feet over cheap AWG10 with min. loss. 12 volts is for cars and toys. if you are considering off grid anything you should forget 12 volt battery bank.

[Logan5]

48 volts is even better more power less amps smaller wire.

[brushstroker]

I had a 24 v inverter at one point but my wife left it plugged in when she turned the generator on and fried it so I had to go back to ok faithful for the time being v it I just bought 4 6v us battery 290 ah batteries on a sweet deal so I need to upgrade my cc and inverter at once could take a month could be 6 months but I will

[bcroe]

So if I dropped a panel for now until I get my hands on some different stuff what would be the max distance I could go with that?

From just a wire loss perspective, 2% is a nice loop loss target, but its not in stone. Here I run about 1.1% peak loss at 400VDC, and
3.2% peak loss at 260VAC. I DELIVER A LOT MORE AC POWER by pushing it past 2%; nothing here is near overload. I am not
willing to dig up my 600' loop of 4 gauge, that was already trenched in long before I moved here and added solar.

And there are lots of times (sunrise, sunset, clouds) when you system will run at a level much reduced from peak. For those times your
% losses will drop in direct proportion, probably well below 2%. So run as many panels as other factors allow.

Copper losses are going to follow the inverse square law, so running at 24V will require 1/4 as much copper as running at 12V to maintain
loses. An MPPT Charge Controller will allow panels with a much higher voltage than your battery, but CCs have limits. I recall 4 gauge is
.00025 ohm per foot, any loop is 2 way. Ohms law reveals all. Bruce Roe

[Mike90250]

You could use the #4 wire, but you loose power in it. You could also do a little virtual array tracking, one pair panels pointing SE, one pair SW, and keep the peak power lower,