Using the Sizing grid , 36 panels in 2 or 3 in series 48V

[CDN-VT]

Im not getting why ?
Rated PV Array Power:    10980    Watts
Anticipated Array Power @ 30C:    10733    Watts
Rated PV Array Current:    100.92    Amps
Battery Charging Current @ 57.6 V:    190.6    Amps
VMP (Maximum Power Point Voltage) :    108.9    Volts
VOC (Open Circuit Voltage):    134.4    Volts
VMP @ -15 C°:    128.4    Volts
VOC @ -15 C°:    152.1    Volts

This is 3 in series 12  Parallel Strings 48 Volts  36 panels

Now lower the voltage in strings so 2 in series 18  Parallel Strings 48 Volts  36 panels

Rated PV Array Power:    10980    Watts
Anticipated Array Power @ 30C:    10733    Watts
Rated PV Array Current:    151.38    Amps
Battery Charging Current @ 57.6 V:    190.6    Amps
VMP (Maximum Power Point Voltage) :    72.6    Volts
VOC (Open Circuit Voltage):    89.6    Volts
VMP @ -15 C°:    85.6    Volts
VOC @ -15 C°:    101.4    Volts



Any thoughts are welcome & Thanks  VT

[dgd]

iMO it would be crazy to even consider this.

You already have each of the 3 Classics running at well below their maximum ratings so all the effort and possible expense of extra combiners and perhaps larger cabling for the higher currents to maybe reduce the working temperature a fraction seems unlikely to offer any advantage.

I disagree with is this assertion by some that the lowering input voltage nearer battery voltage makes the classic run cooler and increases efficiency. Why bother having an MPPT controller if you lower the input voltage to decrease the voltage headroom to allow efficient MPPT operation?


Dgd

[Westbranch]

Im not getting why ?

CDN, what is it you aren't getting?

Using the non temp compensated figures:
your 3S string VOC is at ~90% of the Classics Max V.
the 2S string VOC is at ~60%

Problem is at Negative15*C,  VOC exceeds the Classics limits and will go into hibernation

From the manual:

When the Classic input voltage rises above 150volts it will switch off (stop outputting power). As long as the Classic is in HyperVOC mode, the microprocessor and all other function
s like AUX will continue running. When the input voltage comes back down below 150v (or the rated operating voltage of the Classic, depending on model) the Classic will wake up and start charging again automatically. This could happen in a really cold morning with a system that has a Voltage Open Circuit (VOC) close to the maximum operating input voltage

ADD:typo correction  Negative

[CDN-VT]

CDN, what is it you aren't getting?

Using the non temp compensated figures:
your 3S string VOC is at ~90% of the Classics Max V.
the 2S string VOC is at ~60%

Problem is the 15*C VOC exceeds the Classics limits and will go into hibernation

From the manual:

When the Classic input voltage rises above 150volts it will switch off (stop outputting power). As long as the Classic is in HyperVOC mode, the microprocessor and all other function
s like AUX will continue running. When the input voltage comes back down below 150v (or the rated operating voltage of the Classic, depending on model) the Classic will wake up and start charging again automatically. This could happen in a really cold morning with a system that has a Voltage Open Circuit (VOC) close to the maximum operating input voltage

[/quote]


Thats the part I wasn't getting & for me to see -15C is pushing it most Ive seen here at 300 feet above sea level is -10 so I just add 5c to make sure Im within my limits plus I might see 30c only on the thermometer if it's been in the sun more like -5c to 25c is what I remember . There was a time that we did get snow - f something , but that was in the 70's. I'll run them again and see . Just to make sure.

VT 

Edit add , So I ran the numbers again & used -10c (And that is He!! frozen over to me here)
VOC (Open Circuit Voltage):    134.4    Volts
VMP @ -10 C°:    126    Volts
VOC @ -10 C°:    150    Volts
Im just on the limit  of 150 volt .

Now this is a great forum to read , but it has all the bad things that can happen . Even when we don't know how it was wired or the quality of the wire / wiring etc.

I just stumbled over (read threads) of  a few of classics that had the smoke let go. Im in the process of running the conduit under the roof (attic ) and make sure I get the placings correct for the strings etc.

I felt the same way dgd  with the 3 in series with higher voltage to make the MTTP work better in it's range but it was what Westbank posted that had me in a query ?
Reading this that was also in the sizing chart , but what I forgot to post in the first  post was what Westbank posted from the manual .

BUT ,,BUT I assumed that it was 150V adding to battery voltage  was what this line told me :

Max Non operating VOC (HyperVOC) @ 48V Nominal Battery Voltage    198


OR is this NOT what I"m getting .

thanks WB that was the part  of the manual I had con-fused on a reread & check twice

VT

[CDN-VT]

This was another read that I thought I might be pushing things :
http://www.midnitesolar.com/pdfs/whyHyperVOC.pdf

VT

[Westbranch]

yup, 2 panels it is by that document... unless you run out and get a Classic 200! but then you have to live with lower efficiency.