I have 9 REC TwinPeak 2 Poly 285w panels. I have used the MN Solar sizing tool several times to try and configure more panels at 285 watts STC for a larger Array ... but it looks like I have maxed out at 9, no matter how I configure the Series and Parallel connections. Best I can do is 3S 3P
Is there a way to safely configure more panels into the Classic 150? What am I missing?
Then I thought. The panels are rated at 285w STC ... but will they really ever do that much on my roof? I have never seen more than 2000 watts AND the NMOT rating is 214w per panel. So I ran the numbers using all the NMOT specs from the REC spec sheet. And if I plug those numbers into the Sizing Tool ... it looks like I can run a 3s 4p array and a total of 12 panels.
Is it safe to use the NMOT specs (some spec sheets call it NOCT) for sizing an Array? Is there any other way to get a larger array on a single Classic 150?
Attached are the 2 different results using the sizing tool. One for the 285w and One for the 214w.
The only time I ever see the maximum power output of a PV is when it is well below zero degrees F and sunny in the winter - not much humidity to interfere with sunlight potential . They put out more power when they are colder - at least the silicone type PV do . Sometimes they are even over their sticker rating. But the rest of the year - nope .
I am guessing the design doesn't want too many watts on there so the controller isn't getting so hot . The other consideration is the VOC on those very cold days I mentioned above.
I didn't look at the alternative specs you are using so won't comment on that .
Larry
the problem is a SPIKE in the voltage made by the PV, as noted by others, that occurs at sunrise, in winter, when the sun first hits the panel,, logically at the time the PV is at its coldest.... and exceeding Hyper VOC is not a warrantied item...
It is not good to design a system that will have the equipment , ie CC, run at > 75 to 80% of max values.... beyond those % the excess is usually dissipated as HEAT and excess heat is detrimental to electronics...
If you want more input the safest way is another CC, either a KID or a Classic, array size determines the cost effective choice...
hth
Hi Matrix,
First, have you seen this Document (?):
http://www.midnitesolar.com/pdfs/Classic-String-Sizing-Tool.pdf
You really should use the STC rating when inputting data into the MN String Sizer.
NOCT (Normal Operating Cell Temperature) is probably estimated by the Classic String Sizer. A quick rule-of-thumb to approximate operating conditions for PV Power production, is to multiply STC rated power by 0.75 ...
In your data for STC values, you note that your coldest temperature is 50F. Believe that you are in FL, but is 50 F, essentially the coldest temperature ever recorded for the location of the system?
As it is, the Sizer results note that the Classic 150 will enter HyperVoc at about -99.4 F, in the first set of Sizer results.
On a 24 V system, seems that you really should NOT add one more string of 285 W PVs. Would not suggest adding any more PVs at all. This is one of the main drawbacks of 24 V (and especially 12 V) systems. CCs are rated for maximum current output. A 24 V system can only produce (nominally) half the power of a 48 V system, for the same CC output current, and it seems that you are right about at maximum. There can be small additional differences in the exact difference, based upon the relative differences in the PV String voltages into the CC, and this added effect on efficiency of the CC.
IMO, FWIW, Vic
OK, Thanks. I was pretty sure I was near Max. I have seen a few systems in the "Owner Installed System Pics" forum that were 24v and a few I found were larger Arrays than my 2.5 KW array, So I thought Maybe I had missed something. I would like to add 3 more 285w panels, making my system a 3.4Kw system ... but I guess that is out of the question.
Does the Kid work in with a Classic in Follow me Mode? Does it have any Aux ports?
And no, that we DO get colder than 50*, I was in a hurry and thinking more about average lows and not lowest single lows. The coldest I have even seen it here at night was 15* and that was one night in 14 years. Annually we have a few times where it hits mid-low 20's before sun up. On those days it probably warms to around 45 mid day. So over site in my part. :o Thanks for pointing it out.
No the Kid will not work in follow me with the Classic far as I know.
You can look up the control features in the Kid manual .
Larry
I think you could safely add pv to a classic by setting a sane output current limit to prevent it from running flat out for too long. Maybe something like 75a?
The advantage to doing this would be to use the extra pv to still get a decent amount of current from the array in light overcast conditions.
Quote from: estragon on November 08, 2017, 11:13:19 AM
I think you could safely add pv to a classic by setting a sane output current limit to prevent it from running flat out for too long. Maybe something like 75a?
The advantage to doing this would be to use the extra pv to still get a decent amount of current from the array in light overcast conditions.
Would the limiting be done by settings inside the Classic 150/local app? Or is there some other way to limit current "to prevent it from running flat out for too long"? I think there is also a setting to limit input voltage. Would that help ... to set it say, slightly higher than it is now with a 3s3p array, but limit the input voltage from the array so that a 4s3p array would not exceed the CC's voltage and amp maximums ?
This would obviously not be the best use of the New Arrays potential power, but it would at least allow for a slightly more powerful array that would not exceed the CC's max ratings. And I can get 3 panels cheaper than the cost of 3 more panels plus another Classic 150.
Remind me again what are you trying to do ?
A friends system has a second controller of a different type and we just set that voltage absorb about a volt less than the main controller so it will cut out before the main and not interfere with anything but still add power when the batteries are low.
Larry
Quote from: ClassicCrazy on November 08, 2017, 01:29:16 PM
Remind me again what are you trying to do ?
A friends system has a second controller of a different type and we just set that voltage absorb about a volt less than the main controller so it will cut out before the main and not interfere with anything but still add power when the batteries are low.
Larry
I am trying to increase my array size so that I can get - even just a few 100 - extra watts power off the array. This way I can run a larger hot water heater element off of AUX 1 diversion, without doing a direct connection to the heater with a separate array. The wire runs are just to complicated for that.
I am just looking for ways to increase the arrays output for the least amount of money, or system set up changes. Adding 3 more panels to my existing 3s3p in a 4s3p arrangement would be the easiest and most cost effective. But as of now based on feed back in this thread, I do not think a single Classic 150 can work with a larger array .... unless ... as noted above ... there is a way to limit current and / or voltage from the larger array to keep it with in the operating specs of the Classic 150.
Matrix,
Not much time now ...
I did not run 3S X 4 through the Sizer, you can see what this yields.
One added string of PVs with close (+/- 5% or so), but with fewer watts/PV may let you approach the Max recommended of 1.2 Classics.
Going to 48 V is probably expensive ... Later, Good Luck, Vic
Quote from: Matrix on November 08, 2017, 01:23:04 PM
Quote from: estragon on November 08, 2017, 11:13:19 AM
I think you could safely add pv to a classic by setting a sane output current limit to prevent it from running flat out for too long. Maybe something like 75a?
The advantage to doing this would be to use the extra pv to still get a decent amount of current from the array in light overcast conditions.
Would the limiting be done by settings inside the Classic 150/local app? Or is there some other way to limit current "to prevent it from running flat out for too long"? I think there is also a setting to limit input voltage. Would that help ... to set it say, slightly higher than it is now with a 3s3p array, but limit the input voltage from the array so that a 4s3p array would not exceed the CC's voltage and amp maximums ?
This would obviously not be the best use of the New Arrays potential power, but it would at least allow for a slightly more powerful array that would not exceed the CC's max ratings. And I can get 3 panels cheaper than the cost of 3 more panels plus another Classic 150.
You can limit both/either input and/or output current, from the menu it's under charge->limits. I think it's also settable in LA.
If your bank will take more current, or you have another way to use more current that would be produced by adding a second classic and more pv, you might want to consider doing so. 2 classics running at well under max load would likely last longer than a single classic running flat out, and also gives you some redundancy for when one fails.
Adding another string and limiting current makes most sense if your climate is such that you often get lightly overcast days. I find having extra pv helps get to absorb on days when I otherwise likely wouldn't.
Quote from: Vic on November 08, 2017, 01:59:52 PM
Matrix,
Not much time now ...
I did not run 3S X 4 through the Sizer, you can see what this yields.
One added string of PVs with close (+/- 5% or so), but with fewer watts/PV may let you approach the Max recommended of 1.2 Classics.
Going to 48 V is probably expensive ... Later, Good Luck, Vic
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.
I may just start planning now for another set up 9 panels and a second classic. But boy that is a bunch of wiring. :/ Going to 48v is not really in the budget.
Quote from: Matrix on November 08, 2017, 03:01:40 PM
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, 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?
Quote from: dgd on November 08, 2017, 11:34:49 PM
Quote from: Matrix on November 08, 2017, 03:01:40 PM
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
Quote from: ClassicCrazy on November 09, 2017, 12:51:40 AM
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
Quote from: Matrix on November 09, 2017, 12:39:39 AM
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
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
My guess is you'd never see more than ~2500w output from the 3200w STC rated array.
Quote from: estragon on November 09, 2017, 11:00:36 AM
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
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?
Quote from: Matrix on November 09, 2017, 12:54:55 PM
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
Quote from: Matrix on November 09, 2017, 12:54:55 PM
- 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
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.
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.
Quote from: Bob D on November 29, 2017, 09:58:03 PM
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
Quote from: littleharbor2 on November 14, 2017, 07:48:16 PM
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.
Quote from: harryn on December 10, 2017, 02:02:41 PM
Quote from: littleharbor2 on November 14, 2017, 07:48:16 PM
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
Quote from: harryn on December 10, 2017, 02:02:41 PM
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.
Quote from: ClassicCrazy on December 10, 2017, 03:26:28 PM
Yes 48v is nicer but sure ups the costs of batteries - double of 24v system .
Larry
I disagree. If you require 8Kwh of storage, it needs about the same amount of lead, for both 24V or 48V systems. The 48V bank can be half the Ah of the 24V bank, which makes the cost of either bank, about the same per wh of storage.
Agreed
I only use 24Vdc for one system because it charges my MAN LIFT Genie
As far as cost for 24v compared to 48v it all depends on the size cells you are going to use and if you can find ones half the amp hour capacity for half the price so you can string together the same size battery pack.
Larry
Wow! Being a Total Noob it never occurred to me that 48v would require half the amp hours. Makes sense. And if I would have realized this I would have gone 48v, and for just about 30% more than my 4 435ah batteries at 24v, I could have gone 8 48 v and 265ah but more capacity ? Am see this correctly?
Yep
24V x 435AH = 10,440 W-H
48V x 265AH = 12,720 W-H