Single Classic 150 Max Array Size Help

[ClassicCrazy]

Thanks vic.  I have run Run the numbers thru the sizer at STC for a 285 watt 4s3p array.  Unless there is a safe way to limit things ... 4 285 watt panels in series and using 3 parallel groups is just too large for one classic.  Unless there is a way to do limiting that is safe and effective ... all-be-it limiting the arrays potential.

Matrix,
There is absolutely no need to limit 'things' if you were to connect your 4s3p array to a Classic 150. It does not matter what the array is capable of in power production, the Classic will not be damaged or blow up or let the magic smoke escape,,
All that will happen is that the Classic may current limit at its rated 90+ amps for a 24v battery bank. As long as the classic is mounted in a common sense location where there is sufficient air flow around it then temperature should also not be a problem. You can take some simple steps to mitigate temperature increase, don't cram other stuff next to it, consider mounting it on a plate of aluminium or old large heat sink, etc..
In any case the internal fans will keeps it operating and even if the electronics or pcb get too how then the Classic will shut downuntil it cools down (I have never seen this ever happen with the 40+ Classics i have installed)
As for the nameplate wattage of your PV array, you will often actually get significantly less than this, even on a bright sunny day, maybe 70 to 80% and obviously much less on average days.
Having an over sized array will mean greater daily power into your bank because with low power generating conditions the larger array will raise the minimum power level through the Classic.
My own PV array is twenty 140W PVs in a 5s4p array which nameplates to 2.8Kw with pV voltage 90v into a Classic 150 charging a 24v battery bank. Despite others opinions that the Classic will heat due to the 90v to 28v conversion I rarely hear the turbo fan working even when the output current is 85+ amps.
I have the Classic in a basement garage where temperate varies not to much fron 23c
its on a wood wall with a 400mm by 200mm plate of 10mm aluminum plate behind it and a real thick layer of heat sink compound between them (mostly squeezed out!)

dgd

dgd
I have pretty much the same setup as you -20 135 watt Kyocera panels on one Classic charging 24 v. The fans run on my Classic when it is charging though I have never had any problems or shut downs from it getting too warm. I should try putting it on chuck of aluminum like you did - mine is just on plywood . Of course now that it is winter and will be below freezing for a few months don't really have to worry about overheating !

Larry

[dgd]

I have pretty much the same setup as you -20 135 watt Kyocera panels on one Classic charging 24 v. The fans run on my Classic when it is charging though I have never had any problems or shut downs from it getting too warm. I should try putting it on chuck of aluminum like you did - mine is just on plywood . Of course now that it is winter and will be below freezing for a few months don't really have to worry about overheating !

I have only noticed the ali plate behind my C150 get lukewarm even with 85+A being output.
My PV array was, for a few years, 5s3p or 2100W. Since the array increased to 5s4p and 2800W I can see the extra current in non optimal conditions
The highest power I have logged is 29.2v at 93.8 amps (2734watts) and that was a part cloudy day
dgd

[dgd]

dgd, when u say 'turbo fan' is that the only fan in the classic? My fan runs off and on regularly thru the charge cycle. Is that the same fan as the turbo fan?

The turbo fan is the one in the little tower at top rhs of classic. Its usually very loud when running. The normal internal fans are located at bottom, if you remove the wiring cover they are there just below circuit boards. They run much less noisy and more often
dgd

[Matrix]

I have my Classic up on Plywood, but it is mounted 1/4" off the wood with stand offs at the connection screws.  So Air can move all the way around all sides.  There is nothing blocking or touching anything.  I did use 2 holes, one at the bottom and one on the left side for conduit entry points. 

dgd ... if I upped my array to 4s3p (12) from the present 3s3p (9) ... I would be up at 3,420 for the array size.  A bit larger than yours. Not sure if Mr Classic would be up to the task

[estragon]

My guess is you'd never see  more than ~2500w output from the 3200w STC rated array.

[Matrix]

My guess is you'd never see  more than ~2500w output from the 3200w STC rated array.

I agree ... Right now with a 2,565 STC array ... I never see more than 2000 (and usually less than 1.9kw)

But based on posts at the top of this thread ... most discourage from pushing a classic 150 that hard.    If I upgraded I would be at 3.4kw STC with 2.6 being the NMOT ... (I only ever see NMOT from my present array.  But it has only been up 4 weeks and this is OCT / NOV not JULY in FL)

As noted early in this thread:  3s4p is doable at the NMOT rating,   but not at the STC rating based on the MS Calculator

[Matrix]

What is the concern with the Classic 150 and the Array size??

- If the Array is too big ... will the input Volts or Amps get to be too hi?
- Will the throw the Classic into Hyper VOC?
- Or will it just go up in a puff of smoke?
- Ball of flames on the wall?
- Does the Classic just go to sleep?

[Vic]

What is the concern with the Classic 150 and the Array size??

- If the Array is too big ... will the input Volts or Amps get to be too hi?
- Will the throw the Classic into Hyper VOC?
- Or will it just go up in a puff of smoke?
- Ball of flames on the wall?
- Does the Classic just go to sleep?

Matrix,

As noted in the MN Document,  Linked earlier in this Thread  ...   USE THE STC RATINGS AS INPUT TO THE SIZER,  FOR THE PV CONFIGURATION THAT YOU ARE CONSIDERING   ...   STC.

The Classic will protect itself,  under most conditions,  even when significantly over-PVed.

Primarily,   the output current resulting from over PVing  is the dominant consideration from over-PVing,   if the String Vmp  is reasonable.   Your PVs are toward the high-end of reasonable String Vmp,   but,  with Flooded batteries,  you really have no choice on a 24 V system.

'Tis a busy time here,   and an unable to run the Sizer with 12X 285 PVs, but you would looking at about 85-ish Amps,   or a bit higher output current for a number of hours per day.

Over-PVing  will raise the average Vin into the Classic when the PVs are not fully loaded,   compared to the 3S3P  config.

MN's guidance is  to not exceed 1.2  Classics,   as stated in the Sizer output.

IMO,   the Classic will not shut down when overloaded,  but bill just Limit its output current to manage its temperatures.

Under some Fault conditions,   significant over-PVing an MPPT CC could result in damage to the CC,  if it cannot apply its current Limiting quickly enough  --  FETs could be fried under unusual circumstances   ...   IMO.

Back to work,  here ...  FWIW,  Vic
The Size

[dgd]

- If the Array is too big ... will the input Volts or Amps get to be too hi?
- Will the throw the Classic into Hyper VOC?
- Or will it just go up in a puff of smoke?
- Ball of flames on the wall?
- Does the Classic just go to sleep?

None of these,
The Classic can only 'take' just over 90 amps of current. You cannot force any more into it.  It does not matter how many amps your PV array is capable of, so you can safely connect your 3.5kw array to the Classic.
Same as why your 1Kw electric fire only can take a max of 1Kw despite the fact you connect it to a grid supply capable of providing megawatts.

You only have control of the voltage you connect to its input. You need to ensure that is within an appropriate range to not damage your Classic. Read about HyperVOC in your Classic manual.

dgd

[littleharbor2]

Of course this is a radical (read expensive) change ,but also blatantly obvious.  You could change to a 48 volt system. I'm not trying to be sarcastic, just mentioning a way to add more panels.

[Bob D]

I was wondering the same thing - what happens with an oversized array.
In some communications with Midnite I clarified that there is no issue with "ovepanelling" other than temperature with the Classic putting out max current.
It was suggested that I keep an aye on the FET temperatures, anything under 60C was of no concern and the Classic starts throttling back as the FET's approach 85C. It was recommended that both cooling inlets in the bottom of the Classic are open and clean.

My installation consists of two arrays - one at 2520 watts and one of 1040 watts. They are oriented somewhat differently - the larger one points at solar 11AM and the smaller at solar 1pm. At noon there is nearly the whole output available. However the Classic maxes out at 94 amps, or about 2500 watts. In fact, to be a bit conservative, I set the max output current to 90A.
The highest FET temperature I have seen is 55C with the ambient at 28C.

I don't think the size of the array has anything to do with how the Classic handles things - as mentioned above it only takes what it can use - and so connecting it to a megawatt array would just mean it runs at maximum all the time, if your batteries can absorb the energy.

all FWIW.

[CDN-VT]

I was wondering the same thing - what happens with an oversized array.
In some communications with Midnite I clarified that there is no issue with "ovepanelling" other than temperature with the Classic putting out max current.
It was suggested that I keep an aye on the FET temperatures, anything under 60C was of no concern and the Classic starts throttling back as the FET's approach 85C. It was recommended that both cooling inlets in the bottom of the Classic are open and clean.

My installation consists of two arrays - one at 2520 watts and one of 1040 watts. They are oriented somewhat differently - the larger one points at solar 11AM and the smaller at solar 1pm. At noon there is nearly the whole output available. However the Classic maxes out at 94 amps, or about 2500 watts. In fact, to be a bit conservative, I set the max output current to 90A.
The highest FET temperature I have seen is 55C with the ambient at 28C.

I don't think the size of the array has anything to do with how the Classic handles things - as mentioned above it only takes what it can use - and so connecting it to a megawatt array would just mean it runs at maximum all the time, if your batteries can absorb the energy.

all FWIW.

I agree , & limit max amps out to keep the temps somewhat down when the sun is makin bacon.
In the Winter here in the PNW in a rain forest , I need to grab all i can in the wet season. Come 
Summer I can turn off disconnect breakers Or just watch the temps .

VT

[harryn]

Of course this is a radical (read expensive) change ,but also blatantly obvious.  You could change to a 48 volt system. I'm not trying to be sarcastic, just mentioning a way to add more panels.

This is exactly the reason to use 48 volt systems from the beginning - it makes such a dramatically better use of the hardware.

Another possible alternative though is to mount one string of panels in a direction different than the existing array to better capture morning or late afternoon sun.  It is unlikely that the total combined power from the main array and auxiliary array would over power your controller.

[ClassicCrazy]

Of course this is a radical (read expensive) change ,but also blatantly obvious.  You could change to a 48 volt system. I'm not trying to be sarcastic, just mentioning a way to add more panels.

This is exactly the reason to use 48 volt systems from the beginning - it makes such a dramatically better use of the hardware.

Another possible alternative though is to mount one string of panels in a direction different than the existing array to better capture morning or late afternoon sun.  It is unlikely that the total combined power from the main array and auxiliary array would over power your controller.

Yes 48v is nicer but sure ups the costs of batteries - double of 24v  system .

Larry

[Westbranch]

Another possible alternative though is to mount one string of panels in a direction different than the existing array to better capture morning or late afternoon sun.  It is unlikely that the total combined power from the main array and auxiliary array would over power your controller.

With the added benefit of having a LONGER time for the sun to either End Absorb, to get into Float or Finish Float.. depending on your locale and sun patterns.