Need help figuring out solar panel wiring configuration

[SolarHead]

If you remember, we have the following configuration (which works);

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PV1A & PV1B will be 2 rows of 7 Canadian Solar panels and PV2A & PV2B will be 2 rows of 9 Mission Solar Panels. They can be arranged exactly as you mentioned, 2 rows of 16. Each row will have 7 Canadian Solar panels and 9 Mission Solar Panels.

PV1 has the following specs. Vmp (NMOT per datasheet) = 210V; Imp (NMOT per datasheet) = 15A (7.5A x 2); Voc =276V; Voc @0 deg. C. = 296V
PV2 has the following specs. Vmp (NMOT Estimated) =220V; Imp (NMOT Estimated) = 15A (7.5A x 2); Voc = 397V; Voc @0 deg. C. = 393V

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My question is, what if I want to add more panels to my 32 panel array? with the Sol-Ark having two MPPT charge controllers, both are 500V max, I guess PV2 is pretty close to being maxed out, maybe its maxed out already? The more logical would be to add more panels to PV1, but those are the brand/model that was discontinued which lead me to buying the Mission Solar brand panels and ending up with 2 brands/models. I can buy more of what is used on PV2, but PV2 looks maxed out, I mean its at 393V and 500V max is what the Sol-Ark can handle on each MPPT.

 

[BentleyJ]

NOTE: In reviewing the above data PV2 has 9 panels @ 32Vmp so the operating voltage for the strings should be 288V NOT 220V. I believe I had multiplied by 7 not 9 in that case. Fortunately, no problems were caused as this is still well within operating parameters.

As to your question: Based on the Inverter specifications it looks like you could easily go up to 40 panels. This would be achieved by adding 8 Mission Solar panels as follows.
Add 3 panels to each row of PV1A & PV1B, 6 total for PV1.
Add 1 panel to each row of PV2A & PV2B. 2 total for PV2.
A grand total of 8 new panels + 32 existing panels = 40 panels (2 rows of 20 panels)

Mixing CS panels with MS panels should be OK since their output values are so similar, worst case, there is a small efficiency loss because they are not identical but overall you still get more electricity compared to not adding panels.

Revised PV1 values; Vmp (NMOT per datasheet) = 306V; Imp (NMOT per datasheet) = 15A (7.5A x 2); Voc @0 deg. C. = 427.1V; Input = 4,590 Watts
Revised PV2 values; Vmp (NMOT Estimated) =320V; Imp (NMOT Estimated) = 15A (7.5A x 2); Voc @0 deg. C. = 437V; Input = 4,800 Watts.
Total = 9,390 Watts

Even with 40 panels the system still has plenty of head room for both voltage and current. I wouldn't go above 40, but at 40 panels it looks really good. Even if you get momentary "cloud lensing" phenomenon which can amplify sunlight and cause the panels to produce 100% of their STC ratings, your total input to both MPPT chargers is 12,590 Watts which is below the stated maximum. If you have the budget and the space for 40 panels go for it if you think you can use the extra power.

 

[The Dish Doc]

I've discovered that warehouse 20 foot tall uprights can be found online (Craiglist, etc) for fairly cheap and they have holes that line up well with unistrut holes magically. So, I'm experimenting with this and very little fabrication it seems. I did weld some hinges to it so I can tilt/adjust for winter and summer. I figured 6x6 treated posts in ground, hang the upright horizontally and I can get 9 panels on one upright.

View attachment 85490

Do you have any pictures of your rack that you can share? I'm trying to get some ground mounts built myself and would love to see what you did. Thanks.

 

[SolarHead]

I ended up going with IronRidge. Their design tool took 15 minutes to figure out, it provided a drawing, and a BOM (bill of materials), as well as DWG and DXF files for download all for free. Then I took the parts and found them at various places online price shopping to get lowest price. I sourced the pipe locally.

 

[SolarHead]

Heres what I ended up with, 4 high x 8 wide array. I'm wanting/thinking of adding 4 panels to either end, whichever end can handle the voltage/amperage. It seems both brands and models of panels I have are now discontinued (seem to discontinue quickly from what I can tell or maybe its just bad luck). (side note - my advice, anyone wanting panels, I'd advise you buy your entire array, and maybe one column or row more to put in storage in case you experience a bad panel, or want to add on in future).

 

[TorC]

Yes, panels do seem to change models frequently. However, if there's space, it isn't that hard to find a panel that can replace it with equal performance, though you'd probably get a panel that puts out a little more than the existing and not take advantage of all of that "extra" power. In series, the smallest Isc/Imp will limit the whole string, while in parallel Voc/Vmp will limit the string.