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Mixing Panels of differing Voltage/Current

RoySalisbury

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Joined
Apr 24, 2022
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I understand that when you mix panels of differing voltage and/or current that you only get the minimum of the mixed panels. For example:

45v + 40v = 80v ...
or
8a + 9a = 16a

But what numbers should you use to determine the Voc or Isc of the string? Do you add them up "as they are marked" or do you use the lower Voc of the string?

For example, if have

12 330w panels @[45.83 voc, 37.70 v nominal, 9.27 Isc, 8.76 a nominal]
6 320w panels @[49.5 voc, 40.1 v nominal, 8.6 Isc, 7.99 a nominal]

I'd like to keep the volts as high as I can (within supported hardware) due to cable length, so that would be 450v/27a (6000w). That means a 9x2 array.

6 [330w] + 3 [320w] = [(45.83 *6) + (49.5 * 3)] = [274.98 + 148.5] = 423.48 Voc (for max voltage support)
current would be 9.27a Isc

and
6 [330w] + 3 [320w] = [(37.70 * 6) + (40.1 * 3)] = [226.20 + 120.3] = 346.5 V nominal (to determine yield)
current would be 7.99a nominal

Yield: (346.5 * (7.99 * 2)) = 5537.07 w (a loss of about 1 full panel over rated)

Would this be correct, or should I be looking at things different?
 
For panels in series, add the volts and use the lowest amp value. In series there is one current and that current's value is governed by the least panel's current. For parallel panels or strings, there will be some average voltage. I would avoid mixing different voltages in parallel unless they had the same cell count and were the same cell type.
 
What grid tied inverter/SCC are you planning to run?

If used for off grid, it wouldn’t hurt to run one set of panels to each of their own SCC.
 
I'll be using the LVX6048.

My current system (that I am replacing) is an Outback system, so am used to running multiple charge controllers (I have 4). I'm trying to get away from all the "extra components" wit this build. I'll eventually have two LVX6048 inverters, but when I add the second one I will put in another array of panels with it. So right now I'm trying to maximize what I can on a single device.

I believe my numbers are good, so I think it will work out. But its always good to get other opinions before it all goes up in smoke.
 
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