diy solar

diy solar

long solar MC4 cable run and solar panels

Coz

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Mar 20, 2022
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I will be setting up (4) 200 watt solar panels about 150 foot from the house where my charge controller will be.
My solar generator is a Bluetti AC200MAX.
My max voltage input is 145 volts with a max wattage input of 900 watts from solar.
What I can't figure out or decide is should I have 12 volt or 24 volt solar panels for that long of run?
I had planned on hooking the 4 panels in series.
With the panels I am looking at, the 12 volt ones have a voltage of 24.3 volts each
The 24 volt panels have an VOC voltage of 45.4 volts.
Of course I am new at this so am not sure if when I hook up the panels in series, do I add all 4 panel VOC voltages or just the (2)?
The 12 volt panels will have a combined voltage of 97.2 volts, way under what the MAX can take.
The 24 volt panels though being I would be using four of them to get my 800 watts, would be at 181.6 volts, way over the max voltage input I can have.
I had read, that if I have a 12 volt panel system, the wires would heat up a lot, so keeping the run short is better.
With a 150 foot wire run, I started thinking that I may need a 24 volt panel?
Hoping someone has some answers and enlightenment for me.
thanks
 
the 12 volt ones have a voltage of 24.3 volts each
You can run these 4 in a series and be under the temp adjusted max of 145V.

The 24 volt panels have an VOC voltage of 45.4 volts.
You can run these 2 in series, then connected in parallel (2S2P) which is very common.

I had read, that if I have a 12 volt panel system, the wires would heat up a lot, so keeping the run short is better.
With a 150 foot wire run, I started thinking that I may need a 24 volt panel?
What is the Voc and Isc of your panels? This can be figured out if you provide the details.
 
my 12 volt panels are 200 watts each/ with a Vmp of 20.4v - a Imp of 9.80A a Voc of 24.3v - a Isc of 10.2A - a Vmax of 1000VDC
Temperature range of -40.c - 90.c - max fuse rating of 15A

My 24 volt panels are 200 watts, with a Vmp of 37.6v - an Imp of 5.36A - a Voc of 45.4v - an Isc of 5.83A - a Vmax of 1000VDC
Temperature range of -40.c - 90.c and a max fuse rating ofd 15A

My Bluetti AC200 Max has a input for solar that is 900 watts max and a max voltage of 145 volts.
I will be using 4 panels which will be 800 watts.
But my wire run will be 150 foot from the panels to the house.
I have been looking at 8 gauge wire for the run, don't know if I need that heavy of ga. or not. I want to have the setup bring me the most wattage with the least amount of loss & heat in the wire. etc.
If I go with the 12 volt panels, I know I can run them in series & be under the voltage & wattage of the Bluetti. But I am not sure that a wire run of that long will work under the 12 volt load? Too long? Will the wires get too hot? etc.
If I use the 24 volt panels, then I can only run two panels to stay under my max voltage input. 4 panels would go over my voltage input limit. Problem with having 2 panels only is that is now I am at 400 watts of input & I can go up to 900 watts, so that is an under use of my machine.
But I am guessing that I can use thinner wire on a 24 volt panel with that long of run, and will not have any wire / heat problems with that long of run. I may have all the wrong information though, so am asking the above questions.
thanks
 
If you run the 12V 24.3Voc panels all in series, the array amps will be 10.2A. (2.4% loss, ok)
Screen Shot 2022-03-20 at 12.18.03 PM.png
If you run the 24V 45.4Voc panels, 2S2P, the array amps will be 11.66A (3% loss, borderline)
Screen Shot 2022-03-20 at 12.19.10 PM.png

The 12V panel array with a 10.2A run will be better than the 24V array.

You still need to determine the ampacity of your 8awg wire.

 
Is it a good idea to go with 8 ga wire? or should I stay with 10 ga?
How would I figure the ampacity of the wire?
The 10 ga I have on hand has a voltage rating of DC:1.8KV / AC: 0.6 - 1KV
I don't know anymore than that.
As I am looking for that 8 ga wire I had found earlier, I am now thinking it would be better to stay with 10 ga.
??
thanks
 
Thanks for the info:
I will stay with (4) 12 volt / 200 watt solar panels then with 150 foot of 8 gauge wire.
I plan on using pvc conduit rather than steel. Is that a good idea?
Also wondering if I could wire in another 200 watt 12 volt panel. I know the voltage would still be under the limit I have on the AC200, but it would be over the max watt input. But I am also thinking that rarely do these panels actually pump out the 200 watts and with a long run, maybe definitely not. That would be a total of (5) 200 watt solar panels equaling 1000 watts (100 watts over my 900 max input) & a total of 121.5 volts which is under my 145 max.
 
temp is -40 cel to 90 above c
We can get as cold as 25 below for a couple of weeks in the winter to upper 90's for a few weeks in the summer, otherwise the winter will be 20 above to 15 below for the lows in the winter & upper 60's to upper 80s in the summer.
 
temp is -40 cel to 90 above c
We can get as cold as 25 below for a couple of weeks in the winter to upper 90's for a few weeks in the summer, otherwise the winter will be 20 above to 15 below for the lows in the winter & upper 60's to upper 80s in the summer.
https://string-calculator.morningstarcorp.com/
This will help you figure out your max voc for cold weather among most other things. You can look up your actual panels and just fill in the blanks.
 
temp is -40 cel to 90 above c
We can get as cold as 25 below for a couple of weeks in the winter to upper 90's for a few weeks in the summer, otherwise the winter will be 20 above to 15 below for the lows in the winter & upper 60's to upper 80s in the summer.
I feel like you must be mixing temperature units here. Where on earth does I get to 90c? That's like 195f!
 
Voc 24.3
Guessing .35% temp coefficient
25C to -40C = 65 dec delta

24.3Vov x 65 x .0035 = 5.57V increase
(24.3V + 5.53) x 5 series = 149V
So 5 in series would violate your SCCs max input voltage near 35C
 
  • Temperature Range: -40°C ~ 90°C
Sorry, above is exactly what the panel specs state.
thanks
 
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