I have limited space for panels I am building a structure to mount them in the available space. I can do a maximum of 9.  I've been reading up and doing calculations and the best I could get to do with the space is 545w Canadian Solar. At -5 degrees it gives me a max voltage of 479v.  Then I realized I can't spilt them in 5/4 because I need 6 panel per string to get over the minimum voltage per string at 95 degrees cell temp.

I can't find a viable way to use 9 panels, going down to 7 seems like too little power generation for the cost of the construction, am I missing something? Any advice would be greatly appreciated, my solar dream is fading a bit.

30 minutes ago, Deonlr said:

Then I realized I can't spilt them in 5/4 because I need 6 panel per string to get over the minimum voltage per string at 95 degrees cell temp.

I have 2 strings of 4 each and it starts up the mppts no problem, so 5/4 should not be an issue, may be slightly below optimal but it will work just fine.

51 minutes ago, Deonlr said:

I have limited space for panels I am building a structure to mount them in the available space. I can do a maximum of 9.  I've been reading up and doing calculations and the best I could get to do with the space is 545w Canadian Solar. At -5 degrees it gives me a max voltage of 479v.  Then I realized I can't spilt them in 5/4 because I need 6 panel per string to get over the minimum voltage per string at 95 degrees cell temp.

I can't find a viable way to use 9 panels, going down to 7 seems like too little power generation for the cost of the construction, am I missing something? Any advice would be greatly appreciated, my solar dream is fading a bit.

I presume all 9 on the structure would face the same direction?

Yes, building structure so they face directly North.

14 hours ago, WannabeSolarSparky said:

I have 2 strings of 4 each and it starts up the mppts no problem, so 5/4 should not be an issue, may be slightly below optimal but it will work just fine.

OK that's great news, I did not know how important the minimum voltage is, thought the MPPT wouldn't work below it 

14 hours ago, Scorp007 said:

I presume all 9 on the structure would face the same direction?

Yes I will build structure to face North.

Edited September 17, 20223 yr by Deonlr

What's the inverter maximum voltage?

Just realized it's in the title. The inverter can do 500V. 479V is less than 500V. You will likely never see 479V, so I would not worry about it.

Edited September 17, 20223 yr by P1000

20 minutes ago, Deonlr said:

Yes, building structure so they face directly North.

As you only need 150V to start and once started only 125V I guess your 4 panels should be fine to start the MPPT. As you indicated that 479V is the high level at minus 5 degrees you are 21V away from the maximum so even 9 in series should be fine. Once installed just look at the graphs to see what voltage you are getting if used as a 9 series and do the calculation what they should rise to if the temp was minus 5. This could provide you with a clear answer if it can ever reach 500V on cold days.

Should the 4 and 5 in each string be a problem then you can als way just change to 8 in series then you are save even if you loose the power from 1 panel.

Could you not increase the panels to 10 wired as 5 per MPPT.

While typing I see 10 cannot be used. Also P1000 agrees on using the 9 in series. Only saw it after posting my reply. 😅

Edited September 17, 20223 yr by Scorp007

Thanks a lot for all the responses.

My concern with putting all 9 on one MPPT is this:

It seems the voltage limit is lower per MPPT.  Not sure why is it different from this:

If the 4 panels is an option then I will go that way, should be OK given that the voltage is highest in the morning when panels are cold and you need to start the MPPT.

Adding one more panel and doing 5/5 would be perfect, unfortunately the space available does not allow a bigger structure.

 

 

Edited September 18, 20223 yr by Deonlr
Fixed images

28 minutes ago, Deonlr said:

Thanks a lot for all the responses.

My concern with putting all 9 on one MPPT is this:

It seems the voltage limit is lower per MPPT.  Not sure why is it different from this:

If the 4 panels is an option then I will go that way, should be OK given that the voltage is highest in the morning when panels are cold and you need to start the MPPT.

Adding one more panel and doing 5/5 would be perfect, unfortunately the space available does not allow a bigger structure.

Your images are broken.

Apologies, fixed images

Now I understand. For MPPT range, use the panel Vmp, not Voc. You will find that the 9 panels fit well in that range. The MPPT will derate outside of this range, but you will not be outside of that range unless you are not using all the power from the panels. I suspect you will be lower than 370V during normal operation at full load.

Brilliant, thank you very much for the responses. Going ahead with the 9x545w.