Pushing the limits as they do

[nigel]

Hi
I have a client who is asking if the Classic 150 can cope with the following
He has  12 NSI 230w Panels, His system voltage is 24 volts
The panels are peak power 230w  total STC rating 2760 Wp
Imp7.8,Vmp 29.5, Isc 8.42, Voc 36.6.
His property is located near Valencia , Spain
I would assume we would wire the panels in pairs to keep the Vmp to 59v
Thus its just above the total STC rating of 2700 watts on the Classic 150 power curve with a operating voltage of 90v
Is this OK
Or are we pushing it for longevity of the Classic

Nigel

[niel]

nigel,
i am assuming you are talking series pairs aka 2 pvs in series.

i think you may be confusing the voc and the vmp. if you put 2 in series with the 29.5v vmp it gives you a 59v vmp total. this is the operating voltage and is far below the 90v for the graph. placing 3 in series will give a total vmp of 88.5v and would be near the graph's 90v point.

[nigel]

its the amps Im concernered about come on Gud give me an answer.........?

[niel]

it is a bit over on the amps, but not by much. i am assuming i read the battery voltage you mean to be 24v. running ryan's string calculator it shows excessive, but gave a rating of 1.1 controllers and they say to add another controller at 1.2. this is borderline. the amps in the calculator showed to be 95.8a and the graph shows 91a max so it could limit the amps on some rare occasions.

i would say the 6p x 2s arrangement is pushing it. it shows to be good with 10 pvs as in 5p x 2s. charge amps in this arrangement is 79.9a and the controller number is .9.

not sure if my opinion is what you were looking for or if i answered your question or not, but gud you're welcome.

[boB]

If those modules put out 100 % of their label rating, that would be about 110 amps at 25 volts
which would be over-doing it a bit but still, the current limit would limit that.

What happens when you REALLY overload an MPPT controller and it current limits is that
the input PV voltage rises to reduce the current....  So that 90 volts turns into higher voltage
which makes the controller heat up more. You can see where that appears on the power
limit graphs.   That is a disadvantage of over-designing the PV array.  Just something to
be aware of.

*BUT*, on the other hand, he would most likely rarely actually get that much out of the array.
If he got 80% which is fairly typical, that would be 88 amps and would be OK I think.
I guess that's what you need to look at.

Pushing it 100% is within its specifications and warranty but it is always a good idea to run
controllers at somewhat less than 100% for longest life.

Hey ! I say give it a try...

I'm just glad you're over there too !

boB

[dgd]

...Classic1
Pushing it 100% is within its specifications and warranty but it is always a good idea to run
controllers at somewhat less than 100% for longest life.

I have sixteen 140watt panels into a Classic 150. As it gets into Summer in a month or so with Sun almost overhead I am seeing close to 90 amps (into a 24v battery bank)
The 150 handles it but if I get an ear close to it I can hear a low hummmm.. and sometime an occasional high freq whine. It also does that 20 second
spike down to 0V/0A  more often chnaging from BULK MMPT to LOW LIGHT then climbs back to full current. I watched this happen 5 times  over 50  minutes of 88+ amps today.
Am I pushing the 150 too much?  Its serial number is 879 so I assume its an early model?
dgd

[boB]

...Classic1
Pushing it 100% is within its specifications and warranty but it is always a good idea to run
controllers at somewhat less than 100% for longest life.

I have sixteen 140watt panels into a Classic 150. As it gets into Summer in a month or so with Sun almost overhead I am seeing close to 90 amps (into a 24v battery bank)
The 150 handles it but if I get an ear close to it I can hear a low hummmm.. and sometime an occasional high freq whine. It also does that 20 second
spike down to 0V/0A  more often chnaging from BULK MMPT to LOW LIGHT then climbs back to full current. I watched this happen 5 times  over 50  minutes of 88+ amps today.
Am I pushing the 150 too much?  Its serial number is 879 so I assume its an early model?
dgd

I'm still not sure what you mean by 0V ?? .... The  0 amps I can see, maybe...
Maybe I should see a video of that.  Maybe just a short cell phone video.

As far as hum goes, that's probably the inductors.  I wouldn't worry about it.

boB

[dgd]

I'm still not sure what you mean by 0V ?? .... The  0 amps I can see, maybe...
Maybe I should see a video of that.  Maybe just a short cell phone video.

As far as hum goes, that's probably the inductors.  I wouldn't worry about it.

boB

Sorry that should have been 0W (zero watts) - but it was the humm/whine that concered me as I thought it may be related to the zero events
and/or the 90 amps output.  I will not worry then.. thanks
dgd

[laszlo]

Well I have added some PV over last year since it got so cheap, so I am  occasionally exceeding the amp limit I set on the Classic  (63 AMPs) so my breakers wouldn't trip.

I was a bit curious as to what would happen when the array exceeds the the max amps  I set, but I was pleasantly surprised the controller displays "AMP MAX reached" or something to that effect, and an LED goes yellow on the MNGP.  and the Local software turn yellow. The Classic handles this condition flawlessly.