Suggestions on adding Panels to existing system

[supradupafast]

Good day all,

I am looking to adding additional panels to an existing system, and wanted some feedback from the more experienced DIY'ers.
My current system consists of :

Rover 60 - @ 24VDC (max: 140VDC , 60Amp, 1600W @24VDC)
Currently have 8 eco-worthy 100w Panels (spec ea. 24.5 VOC, 100W, 5.2A)
Panels are in two strings 4S + 4S , giving me +- 100VOC, +- 11A .
Panel Orientation is 4 facing east / 4 facing west

I have 3 extra Renogy Panels, with slightly different VOC than my existing Eco-Worthy panels (22.3V vs 24.5).
I don't plan on adding on the east facing roof due to shade from trees , but the west facing side, where i'd like to add more panels.
Would it be okay to keep the 4 existing panels in Series on the East - giving me 100VOC , while reconfiguring/adding to the west side ?
I was thinking keeping the existing 1 string of 4 in series, + adding a string of 3 in series west roof (7 total west / 4 east). From what I understand, the voltage should still be under 100VOC, and giving me approx 1100W total , well below the Rover 60's 1600W/140VDC max limit.
To summarize , 3 strings total, 2 strings of 4 Series, 1 string of 3 Series (maybe i can buy an additional panel to make it 3 strings of 4S each)

Hopefully this makes sense, and any input would be appreciated.

 

[sunshine_eggo]

I was thinking keeping the existing 1 string of 4 in series, + adding a string of 3 in series west roof (7 total west / 4 east). From what I understand, the voltage should still be under 100VOC, and giving me approx 1100W total , well below the Rover 60's 1600W/140VDC max limit.

No. Parallel strings on the same MPPT must be the same voltage.

4S in parallel with 3S will:

1. Behave as 3S
2. Deliver nothing as the 4S short circuits through the 3S string.

Depends on how robust the MPPT algorithm is.

With 4S you're dangerously close to 100Voc in cold weather. If it EVER gets below -5°C, Voc will exceed 100V, and you may pop the controller.

IMHO, 3S3P is your best option with all panels in each string facing the same direction provided the Imp are comparable. The 3 additional panels likely have a lower Imp, and they will drag the others down to their level meaning you may get little to no benefit with 9 panels vs. 8.

 

[supradupafast]

No. Parallel strings on the same MPPT must be the same voltage.

4S in parallel with 3S will:

1. Behave as 3S
2. Deliver nothing as the 4S short circuits through the 3S string.

Depends on how robust the MPPT algorithm is.

With 4S you're dangerously close to 100Voc in cold weather. If it EVER gets below -5°C, Voc will exceed 100V, and you may pop the controller.

IMHO, 3S3P is your best option with all panels in each string facing the same direction provided the Imp are comparable. The 3 additional panels likely have a lower Imp, and they will drag the others down to their level meaning you may get little to no benefit with 9 panels vs. 8.

I understand, but the Rover60 can go to 140VOC
So I guess it's either I keep Equal sets/strings in numbers, or leave it as it is.
Thanks for your input.

 

[sunshine_eggo]

I understand, but the Rover60 can go to 140VOC
So I guess it's either I keep Equal sets/strings in numbers, or leave it as it is.
Thanks for your input.

Ah. I see that now. Missed it in the original post.

In that case 5S2P might make more sense if you can have each string on the same facing.