Series panels

mike95490 · June 2018

mike_s said:
mike95490 said:
But if you have a string of panels, and some shade hits parts of some of them, your array voltage may drop enough the system shuts down.
The discussion was comparing series vs. parallel panels. There is no case in which a parallel connected system would continue to provide power with the same shading which would drop a series connected system below the system voltage. So, what's your point?

My point was that the original post, it was series panels.

Renogy sells a 12 volt 500 watt kit. 150 volt cc with 5 100 watt panels in series. Can some one explain why this is a bad idea?

Now you are changing the OP's 5S array to a array of you choosing, to prove a specific point only you know. And this answers the OP's question how?

mike_s · June 2018

mike95490 said:
Now you are changing the OP's 5S array to a array of you choosing, to prove a specific point only you know. And this answers the OP's question how?

Nope. Try to keep up. Mcgiver said the disadvantage of series strings was that shading on one affected the whole string. I pointed out that was incorrect. He doubled down, so I detailed why, including a comparison.

Estragon · June 2018

Sorry to interrupt the pissing match, but some of us are still learning here. It seems to me @mcgivor is correct in that "shading of one affected the whole string", and the degree to which the string is affected depends on whether bypass diodes /rectifiers are in parallel with a cell, group of cells, group of panels, etc., and how the shade falls.

Not doubling down, just trying to learn.

mountainman · June 2018

Sorry that my question opened such a can of worms.Just to be clear the only shading is briefly when then sun comes up from behind the trees and goes down.So my understanding is parellel is better for shading. The best configuration would be to put 2s 3p 6 panels on 45 amp cc. 2nd best would be 3s 2p and lastly all in series would be harder on cc because of excess heat. all in series at 22.5 voc is 112.5 x 1.25 is 140.625. Panels Temp Co eff of pmax -0.44/°c as to the reply of over 150 volts in cold weather -17.78 c is the lowest temp wouldn't that be 42.78 x .0044 roughly. 19% 112.5 × .19 =21volts 134 total???

mountainman · June 2018

And to add why my interest in all in series I need 500 watts for 125 foot array on the 8 awg I already purchased.

mcgivor · June 2018

mike95490 said:

mike_s said:
mike95490 said:
But if you have a string of panels, and some shade hits parts of some of them, your array voltage may drop enough the system shuts down.
The discussion was comparing series vs. parallel panels. There is no case in which a parallel connected system would continue to provide power with the same shading which would drop a series connected system below the system voltage. So, what's your point?

My point was that the original post, it was series panels.
Renogy sells a 12 volt 500 watt kit. 150 volt cc with 5 100 watt panels in series. Can some one explain why this is a bad idea?
Now you are changing the OP's 5S array to a array of you choosing, to prove a specific point only you know. And this answers the OP's question how?

mike_s said:

mike95490 said:
Now you are changing the OP's 5S array to a array of you choosing, to prove a specific point only you know. And this answers the OP's question how?

Nope. Try to keep up. Mcgiver said the disadvantage of series strings was that shading on one affected the whole string. I pointed out that was incorrect. He doubled down, so I detailed why, including a comparison.

The point regarding shading was to bring up one aspect where a series configuration could experience losses, it was for the benefit of the OP, the parallel comment was merely a comment nothing more, not a comparison. There are obviously advantages and disadvantages to both, or there would never be a need for one over the other. Thinking one is superior over the other in all circumstances is flawed, which is why I pointed out the advantage, series, MPPT, over parallel, PWM. If I believed parallel was always superior I would never use series, but I do. So the discussion was never intended to be a comparison, it became one without intention, my apologies to the OP.

Estragon · June 2018

The temp coefficient is calculated for the string, so if it works out to 3v, in a string of 2 panels that would increase string Voc in the cold from ~22.5 x 2 = 45v to 22.5 + 3 = 25.5 x 2 = 51v

With 3 strings of 2, and panel current of ~5a, combined current would be ~15a. 125' of 8ga gives a drop of a bit over 5%. 2 strings of 3, ~10a at 67v a drop of a bit over 2%. Either would be ok IMHO. With only 2 strings, fuse/breaker per string is optional.

Early morning and late afternoon shading doesn't matter a lot much of the year, as the sun is low (weak) and angled east/west, so you wouldn't be missing a ton of production. It can matter in winter though (especially if the sun doesn't clear the trees mid-day).

mcgivor · June 2018

Estragon said:

The temp coefficient is calculated for the string, so if it works out to 3v, in a string of 2 panels that would increase string Voc in the cold from ~22.5 x 2 = 45v to 22.5 + 3 = 25.5 x 2 = 51v

With 3 strings of 2, and panel current of ~5a, combined current would be ~15a. 125' of 8ga gives a drop of a bit over 5%. 2 strings of 3, ~10a at 67v a drop of a bit over 2%. Either would be ok IMHO. With only 2 strings, fuse/breaker per string is optional.

Early morning and late afternoon shading doesn't matter a lot much of the year, as the sun is low (weak) and angled east/west, so you wouldn't be missing a ton of production. It can matter in winter though (especially if the sun doesn't clear the trees mid-day).

Wrong thread perhaps?

Estragon · June 2018

Responding to posts #35/36?

mcgivor · June 2018

Estragon said:

Responding to posts #35/36?

Sorry, my mistake

mike_s · June 2018

mcgivor said:
The point regarding shading was to bring up one aspect where a series configuration could experience losses, it was for the benefit of the OP, the parallel comment was merely a comment nothing more, not a comparison. There are obviously advantages and disadvantages to both, or there would never be a need for one over the other. Thinking one is superior over the other in all circumstances is flawed, which is why I pointed out the advantage, series, MPPT, over parallel, PWM. If I believed parallel was always superior I would never use series, but I do. So the discussion was never intended to be a comparison, it became one without intention, my apologies to the OP.

Parallel also experiences losses due to shading. So, you're saying you had no point?

Parallel does not imply PWM. With a 12V system, one might gain a few percent with MPPT, or use it with panels having more cells (e.g. 48+). The main reason for parallel with PWM is lower cost per watt for smaller systems.

mcgivor · June 2018

@mike_s
Not going to bite

Series panels

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