Any issues with 12 panels in series as opposed to 6s2p?

[Britman]

Guys
Just about to put the panels on my new array rack.
Please chime in on panel configuration .. I’m planning
On
12 x 400w all in series

400/31v(vmp) = 12.9a(imp)
12x 31v = 372v (under my MPPT LIMIT of 450v)

Fused at 15a

Any draw backs to this over

6s2p ?

I HAVE NO SHADE ISSUES

Thanks!

 

[scrubjaysnest]

Voc?

 

[RCinFLA]

If Vmp is 31v, then Voc will be about 31v/0.85 = 36.5v.

36.5v x 12 in series = 438 vdc Voc for array, at whatever temp the Vmp is spec'd at (25 degs C or 40 degs C typically). Then apply cold temp coefficient on top of that.

Depends what temp the Vmp is spec'd at and your coldest temperature expected but cold temp Voc will likely exceed 450 vdc.

438vdc x -35 degs C delta from Vmp temp spec x -0.4%/°C temp coefficient + 438vdc = 499 vdc max at cold temp.

You have to use Voc for max voltage as an MPPT controller will approach Voc input voltage as it does initial MPPT search.

 

[SeaGal]

36.5v x 12 in series = 438 vdc Voc for array, at whatever temp the Vmp is spec'd at (25 degs C or 40 degs C typically). Then apply cold temp coefficient on top of that.

If he's in UK (as the name suggests) then would have to assume -15C lowest temp, so with Voc at +25C there'll be a minimum +10% increase in Voc at low temp (diff of 40C @ approx -0.25%/C). So max Voc, as you say is too high being 482V min

 

[Britman]

If Vmp is 31v, then Voc will be about 31v/0.85 = 36.5v.

36.5v x 12 in series = 438 vdc Voc for array, at whatever temp the Vmp is spec'd at (25 degs C or 40 degs C typically). Then apply cold temp coefficient on top of that.

Depends what temp the Vmp is spec'd at and your coldest temperature expected but cold temp Voc will likely exceed 450 vdc.

438vdc x -35 degs C delta from Vmp temp spec x -0.4%/°C temp coefficient + 438vdc = 499 vdc max at cold temp.

You have to use Voc for max voltage as an MPPT controller will approach Voc input voltage as it does initial MPPT search.

voc = 37 +/- 4% 25'c TEMP

I'm in eastern NC

 

[Britman]

Voc?

37 +/- 4% temp 25c

 

[Britman]

It was suggested on a FB solar group that i should go with 2s6p for 70a .... apparently that is the most powerful ?
I heaven't heard that before as the KWh remains the same... and more crucially i don't have 50' of 2/0 wire lying around

 

[Reed Cole]

6s2p? Wire size should be a little more reasonable.

 

[Supervstech]

2P would only be 26A max… #8 should handle it just fine…