Ground deploy panels, how long wires?

[RoadTurtle]

I kept two 200w 12v panels that I removed when I upgraded to 24v panels. We have an event this summer, and going to set the two panels to supplement roof panels. For this event, trees will not be an issue. What's a good wire length to get started with?

 

[OzSolar]

I kept two 200w 12v panels that I removed when I upgraded to 24v panels. We have an event this summer, and going to set the two panels to supplement roof panels. For this event, trees will not be an issue. What's a good wire length to get started with?

If you told us the wire size, the amperage and the max voltage drop you're shooting for we could answer the question.

 

[chrisski]

Also the length it needs to be. 200 watt panels will likely be around 10 amps in series and 40 volts, or 20 amps in parallel at 20 volts. Shade not a factor should make series the preferred way for small wire.

 

[RoadTurtle]

(2) 200w 12v panels. Leftover PWM SCC can't accept series, so parallel.

 

[Crowz]

Again as mentioned amps and wire size is key.

So 10amps with 10 gauge wire can go 100 feet with 10% loss (not ideal).
3% loss which is what I usually go by is 30 feet.

Larger wire can go further. Smaller wire will need to be shorter.

 

[RoadTurtle]

Not a question of how long can I go, but what have people found to be a usable length. 100' with no trees is pretty long. I'm trying to limit the wire length. Thinking along the lines of 20+ ft, but want to hear what people have found as a usable length

 

[Ampster]

what have people found to be a usable length

Usable length is not a familiar term in electronics. If you would answer the simple questions other posters have asked you might get a useful answer. The quesion is what voltage will you be sending down that wire and how much voltage sag can your PWM SCC tolerate? If you could put those panels in series the voltage sag would be decreased. What is the minimum voltage that your PWM charge controller can accept? Then you can calculate voltage sag based on wire size, length and the voltage of the panels in parallel. That will give you the maximum distance for a particulat wire size. Increasing wire size will mean less voltage drop.

 

[chrisski]

Before I did calculations, I cut wire I had for a battery charged by a solar panel. I found it was not a “usable length” when I found my battery dead then measured with a volt meter and found 50% voltage loss in the wire making the panel voltage received at the battery 9 volts for a 12 volt battery.

I then started doing calculations and have not had trouble since. The math is not that hard and you actually put four numbers in a calculator on a website:

length (more length more loss)
Amps (more amps more loss)
Volts (more volts less loss)
Wire gauge (thicker wire less loss)

All four of those work together and without an answer to all four, you’ll just be guessing.

 

[wiseacre]

Usable length
In winter I have cables that are just long enough
In summer they're extra long

Two movable, adjustable tilt racks I move around seasonally to avoid shading

 

[Ampster]

Amps (more amps more loss)
Volts (more volts less loss)

That is why nine in series would get more "useable length" out of the same size wire than the other configuration with more Amps and less Volts.

 

[Scott SD]

I use (2) 100w panels in series for a ground deploy array and use a Victron 75/15 mppt. I have a few sets of 12awg cables and try to use the shortest possible, usually 20'. It works perfect on my 12v system. If you are 24v, even better.

 

[wme]

FWIW My set up...2 100w panels, 25ft 10ga wire, ancient CC with SLA settings, 50 amp Anderson's connectors. Because the panels get the proper angle and direction I get 9+ amps