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zorro
Member
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# Posted: 19 Apr 2021 09:48 - Edited by: zorro
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This is a follow on to my "Replacement Batteries" posting
I am hopefully heading back to the cabin this weekend with 8 new batteries (after the year old set totally froze) and will need to try to check my system and also add a breaker to the stand alone charger
If in the even that I do need a new charge controller, can anyone suggest a replacement MPPT CC around the $300 mark?
It needs to be able to handle;
24V battery bank
3 x 340W PV
60Amp
Currently i have a ML4860, which is only around 12-15 months old (without the BT module);
https://amzn.to/3v5WFSP
From the other thread, you will see i had a major failure, but as yet, not sure where the issues were and what caused it
Replaced the Inverter last year
New Batteries this week
Panels seem to be outputting correct levels
Wiring appears to be correct
So trying to narrow down where the issue is this weekend
So any suggestion for a replacement CC 9if it comes to that), or should i just get the same CC again?
Any views?
Thanks
Paul
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Nate R
Member
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# Posted: 19 Apr 2021 09:54
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Morningstar Prostar MPPT? Cheaper than their Tristar stuff, but for <1100W, and 24V, it's no problem.
Their stuff has been rock solid over the years. A bit pricier, but I think worth it. I've been using mine for 18 months now, I think? Been great to download historical data and see my daily battery voltage minimum, how long it was in Absorb or float, etc.
I have the cheaper version with no meter on it. (And a 25 Amp version.) Been fine, I use a laptop to update firmware for my battery specs, and see how things have been going.
I've even been able to datalog (every 5 minutes) my solar panel output over many days this way when I'm there. This has helped me see how much sun my panels are ACTUALLY getting and how much panel I would have needed, etc.
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zorro
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# Posted: 19 Apr 2021 10:13
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Thanks for the reply
I dont see that in a 60amp version?
Only think i can see is the Tristar option;
Morningstar TS-MPPT-60 Tristar 60 Amp MPPT Charge Controller
But that comes in around $600
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Nobadays
Member
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# Posted: 19 Apr 2021 10:32
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For a cheaper SCC EPever are pretty well thought of... I use a 40amp one on a small 24v system in my shop.
They do make a 60amp HERE
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paulz
Member
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# Posted: 19 Apr 2021 11:38
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My two EPever 40s have been excellent. Do you ever see over 40 amps?
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Brettny
Member
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# Posted: 19 Apr 2021 11:51
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Would two 30a CC be better? You could split arrays up a bit...but with 3 pannels that could be a problem.
Did you ever see 42A with the old CC?
I have an EPever BN series 40a. The one with no screen on it and the whole unit looks like a heat sink. I was told once that the screens on the unit are nearly useless for motoring things as where the CC should be and where the monitor can be viewed may be a very different area. I have 460w of solar at 12v and have never seen more than 24-26a when the pannels should be putting out max of 38A. I wouldnt have a problem putting another 230w pannel on this 40a CC...but my current roof wont fit it.
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zorro
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# Posted: 19 Apr 2021 11:53
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Thanks for the recommendations guys - appreciated
Hoenstly, no idea if it has gone above 40amps
When fitted, the "solar guy" told me it had to be a 60amp CC that i installed..........and just went with that
Funny enough, the one you linked to was what I had initially picked during my build but my solar guy recommended the other ML4860 and sold that to me instead
No sure yet if it is the CC that is the issue, but just wanted to get ahead of the game and not lose another 8 batteries in the process.........least they wont freeze in for a few months, but if the CC is not working correctly, they may not fully charge either - so i need to get that checked out
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Nate R
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# Posted: 19 Apr 2021 12:29
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Zorro, you don't need 60 amps if your controller can handle what it's rated at. Morningstar gives you the temps at which it will handle the amperage...And they usually are conservative.
Your panels might put out more than 40 amps at the very peak output power on the sunniest clear day for 20 minutes......IF your wiring is thick enough...Not sure about others, but Morningstar's MPPT is just limiting output to 40A, they can take more panel than that in.... So no problem.
How are your panels wired? Series or Parallel?
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zorro
Member
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# Posted: 19 Apr 2021 12:33
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Panels are wired in series
3 panels - 340W each
Specs are here;
STC Power Rating 340W
PTC Power Rating 310.61W 1
STC Power per unit of area 16.5W/ft2 (177.7W/m2)
Peak Efficiency 17.77%
Power Tolerances 0%/+2%
Number of Cells 72
Nominal Voltage not applicable
Imp 8.95A
Vmp 38V
Isc 9.53A
Voc 46.6V
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gcrank1
Member
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# Posted: 19 Apr 2021 13:28
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If Ive got this right...
The most important right up front is the VOC input from the array to the scc. With each of your 3 at 46.6V, in series, that makes 139.8, then add 20% for cold weather spikes makes 168. Iirc if you get that wrong and the input spikes it can kill a scc pretty quick.
With the amps output you will only reach max under ideal conditions with a depleted bat-bank (the amps delivered to the bank will only be what the bank can take). My take-away on that is you want a bit of 'overhead capacity'; ie, IF a scc could put out 55A Id be comfortable with a 60A unit
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Nate R
Member
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# Posted: 19 Apr 2021 13:48
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Morningstar Prostar have a 100V max, IIRC. So that won't work. Tristar can do least 150V, IIRC.
But if you're at 46.6V, like gcrank1 says, you might be in trouble. Might be what killed your old controller...I believe that supposedly has a 150V max.
What's missing from your panel specs is the
temperature coefficient.....
If those panels have a common temperature/voltage relationship, you might be overloading your old CC at any temps below 0C or 32 F!
See this link: URL
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zorro
Member
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# Posted: 19 Apr 2021 14:01 - Edited by: zorro
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Here is some further info on the panels;
Temp. Coefficient of Isc 0.05%/K
Temp. Coefficient of Power -0.41%/K
Temp. Coefficient of Voltage -0.149V/K
Series Fuse Rating 15A
Maximum System Voltage 1000V
and where the cabin is, over the winter, the temp was regularly well below 0F (yes, F)
and the original CC, as recommended by the solar guy was only a 150V max
And even the Epever 60A CC above looks as though it only takes a max of 150V on a PV Open Circuit?
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Brettny
Member
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# Posted: 19 Apr 2021 14:32
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My BN series EPever controller will take 150v. That's alot of the reason why I got it over the other ones they sell. 150v would allow me to run 3 pannels in series.
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zorro
Member
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# Posted: 19 Apr 2021 14:42
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Thanks Brettny
If the calculations above are correct though, 3 x 340W (46.6V) panels, in series could easily exceed 150V, especially in winter?
If that is the case, then I am not happy as that is the system which was soled to me!!
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Nate R
Member
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# Posted: 19 Apr 2021 14:46
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OK, so a deg is the same increment as C....
So, 0F is about -17C. Panel specs are standardized at 25C. Open circuit voltage goes UP in colder temps, and drops at higher temps. So 42 C/K difference between 0F and rated temp..... 42 x 0.149 = 6.26V.
46.6 + 6.26 = 52.86V. x3 panels, you're at 158 volts at 0 deg F. Ouch. Seems like a lot of controllers go up to 150V. Either you need to find one that will do 175+V, or think about rewiring your panels to parallel and run some thicker/double/extra wires to the CC.
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ICC
Member
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# Posted: 19 Apr 2021 14:50
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Quoting: zorro the original CC, as recommended by the solar guy was only a 150V max
I don't know all the details of how this equipment was selected and sold to you. If this was a package put together by your solar guy then he should have asked you...
...what is the coldest air temperature at the install location?
...what is the highest air temperature there?
I plugged the spec values for the solar panels (I assume he sold them to you) as well as the max/min air temperatures, the battery voltage and the total number of panels into the Midnite Solar Classic Sizing Tool. This is a great planning tool. All the major equipment manufacturers have such an online tool specific to their equipment. The off brands don't and leave you to twist in the wind on your own.
I also plugged that info into the Midnite Kid sizing tool, but the Kid CC cannot handle those 3 panels in series. And it can't handle the 3 in parallel with a 24 volt battery. The Kid would work 3P with a 48 volt battery though.
The Midnite Tool shows that their Classic 150 volt charge controller would be marginal. It suggests that their 200 or 250 volt controllers would be a better choice. The Classic 150 would be fine with all 3 panels parallel and with a 24 volt battery.
Your solar guy should have realized there could be problems with his suggested items, if he had asked you the right questions and if he know what he was doing.
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zorro
Member
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# Posted: 19 Apr 2021 15:04
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This is crazy!!
So the guy did sell me the CC, panels, and Inverter - only thing he did not sell me was the batteries
However, he 100% new the batteries would be 24V and that the panels would be in series
He also 100% knew where they would be installed - no question
So looks like this CC may not have been suitable for the job required
So, what would be the easiest solution here do you think?
Looks like in my basic understand it would be;
Change panels to parallel
Us the Midnight Solar CC, here;
https://bit.ly/2RMdtjE
at around $670 or so?
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ICC
Member
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# Posted: 19 Apr 2021 15:15
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Am I correct in thinking the original array was setup with the 3 panels in series? Was there a reason for choosing a series configuration?? What is the distance from the array to CC? What size wires are running from array to CC?
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zorro
Member
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# Posted: 19 Apr 2021 15:22
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Honestly, i just went wth the "solar guy" in terms of the set up and series of the panels
I would estimate panels to CC is around 40'
Here is the full order;
3 Hansol 340W Solar Modules
1 Set Iron Ridge Mounting Rails with Roof Flashing
1 Set MC4 Array Cable - #10 Tray – up to 40’ long
1 80A Array Circuit Breaker – Panel Mount - Inverter
1 63A Charge Controller Circuit Breaker
1 30A Array Circuit Breaker
1 Mini-Disconnect – Pre-wired
1 SRNE 60A MPPT Charge Controller
1 SR-RM5 remote Meter for the CC
1 Samlex 1500W 24VDC Sine Wave Inverter
1 Inverter Disconnect Wiring in Pre-Wire plus cables to the battery bank
1 Negative Bus Bar
6 2 Ga. 12†Battery Cable
2 2/0 Ga. 12†battery Cables
16 Battery Anticorrosion Rings
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Nate R
Member
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# Posted: 19 Apr 2021 16:13 - Edited by: Nate R
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Seems like the way to go to me. Go parallel and get a CC that can handle the full output, or the Morningstar Prostar MPPT 40A and save a few bucks. You'd only lose a few % of the power from the panels at peak output, but that might already be "gone" depending on teh wiring.....If it's 40 feet, you could probably get away with leaving the 1 set of 10 ga wires, but make sure they are labeled as 10ga. You'd lose a bit of power through them.....but if you are able to run a 2nd set, you'd be in a reasonable range. URL
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gcrank1
Member
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# Posted: 19 Apr 2021 17:02 - Edited by: gcrank1
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My guess is he wasnt up to speed on the cold temp spike....many havent been.
Underestimating on usage/watt-hrs and overestimating on solar system output is another, as well as a grossly oversize inverter on a given size bat-bank.
Then the always present, inadequate wiring bugaboo.
Where is The Little Golden Book of DIY Solar Electric and/or Solar for Dummies/101?
IF your scc is toast, the winter spike might have done it in as well as your batteries. Does he bear any responsibility in the costly affair? Maybe. Sounds like you 'contracted' in good faith rather than being like me and barging ahead making my own mistakes. Well, I do know how to kick my own butt, been doing it for years!
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zorro
Member
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# Posted: 19 Apr 2021 18:06 - Edited by: zorro
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I have sent the "solar expert" an email to ask the questions.........I dont expect any positive outcome really!
So ..........my decision boils down to I believe 2 options, assuming the CC is toast......but either way, it does not seem to be fit for purpose, especially in winter!
Leaving current wiring "as is", should i go the route of;
1 - parallel for solar panels and the Morningstar Prostar MPPT 40A
https://bit.ly/3alWTxy
around $440
OR
2 - parallel for solar panels and MidNite Solar Classic 150 MPPT
https://bit.ly/2RMdtjE
around $680
Both are more than i wanted to pay, but I REALLY need to get this correct this time around, before my wife kills me 
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ICC
Member
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# Posted: 19 Apr 2021 18:20
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Quoting: gcrank1 My guess is he wasnt up to speed on the cold temp spike....many havent been.
I'll cut people slack, but when one is selling PV equipment in a cold climate they should know that. Maybe the customer cannot be expected to know that but the seller sure should.
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zorro
Member
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# Posted: 19 Apr 2021 18:25
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I definitely didnt know that and honestly would never have guessed
But he MUST/SHOULD have known, based on where he lives and where he supplies to - he knew 100% these would be in upstate NY and subject to extreme cold in winter, compounded by the lake effect as well
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zorro
Member
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# Posted: 19 Apr 2021 19:42
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So if I put the 3 panels in parallel (each PV = 46.6V/340W), total output voltage for all 3 should be 46.6V and should be around 1020W?
If so, can I now use the EPEVER 60A MPPT Charge Controller with a maximum voltage of 150V
Is that correct or do i need to go down the MidNite Solar Classic 150 MPPT route?
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ICC
Member
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# Posted: 19 Apr 2021 21:29 - Edited by: ICC
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If the PV array to CC wires are 10 gauge and 40 feet long and connected to the panels in parallel, the maximum voltage during most operation time will be between Vmp and Voc, between 38 and 46 volts, more or less.
The voltage could be lower on a hot day; voltage climbs when it gets colder, voltage drops when it gets hotter. The amps and volts given in the specs are what would be expected when the temperature is 75 F.
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Voc is usually only seen in the early morning as the panels are receiving first light, but not yet enough brightness to make the CC electronics turn the charging system on. The current flow is zero. The "oc" stands for open circuit if that was not understood. The problem arises when it is cold because that Voc will get higher as it gets colder. As soon as there is enough energy present for the CC to turn on all that voltage hits the downstream electronics and can cause a problem. All that voltage is already contacting the electronics before the device that will finally turn on circuits all on. So, they could be damaged right away. With the circuit closed, amps will flow and the Voc value will drop down. However, that high voltage, even if brief, may have done damage.
I am skeptical about when CC literature states their unit will shut down if the PV voltage goes above a certain value. I don't think it is good practice to make electronics use their "fail-safe" protection repeatedly and expect a long life. I could be wrong as I do not have formal electronics engineering training.
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If the sun is shining brightly the amperage output of a single panel should be Imp= 8.95 amps. Call it 9 amps x 3 panels for 27 amps total.
When the voltage is 38 volts there would be approx. a 3.8% voltage drop. If it was cold outside The voltage could/should be higher. If the voltage was 46 volts with the same 27 amps then the voltage drop is reduced to 3.13%. Those are not ideal % drops but not all that bad. If the sun is off angle or it is slightly cloudy the amperage would fall. If the voltage was at 40 volts and each panel putting out 7 amps, 21 amps total, the voltage drop comes out at 2.8%. Better. So IMO, the 10 AWG MC4 cables should be satisfactory.
If the panels are reconfigured to three in parallel there should be a fuse or breaker in each + wire before they are combined into one output line to the CC. There are some exceptions to this but to make life simpler and safe it would be advised to have a fuse in each PV panel + line. The size would be the Isc value x 1.56. So, 9.53 amps Isc x 1.56 = 14.86. A 15 amp fuse would be fine. (from the NEC where they use Isc x 1.25 x 1.25)
Then after the fused outputs are combined there should be another fuse or breaker sized to handle the max combined array output plus the x1.56 safety factor.
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The EPEVER should work as long as the total wattage of the three panels also does not exceed the specs on that CC. That max wattage of panels varies with the voltage of the battery used. That should be listed in the specs. I have not looked.
FYI, the amperage rating of a charge controller is the output to batteries maximum amps, not the incoming from the PV array.
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Just FYI, when considering temperatures it is the "real" temperature that matters. Wind chills do not have any effect on inanimate hardware. The hardware will cool down faster when the wind blows on it but the temperature of the hardware will not drop below the ambient air temperature.
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gcrank1
Member
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# Posted: 19 Apr 2021 22:25
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"the seller sure should (know)", I agree, but.....it aint worked out that way through much of my life. Cant tell you how many times Ive gone to talk to 'the pros' for something Ive got problems with and find out they cant answer my questions adequately or (shudder) I know more than they do. Guess I should also tell you my wife says I 'research things to death'. Ive always had this need to know how stuff works.
Nice that ICC is able to fill in some of the blanks in layman's terms!
My inclination was to recommend 8ga. wire for that 40', good luck for you that the 10ga. will be Ok (at least to get up and running this season. Im tending to go for all I can get rather than lose output to line losses. Though I just heard today from an electrician that wire prices are at least as bad as lumber right now!
So, fuse the panels, fuse the gang, and you should probably look at your array grounding too?
Maybe all this has figured out your system failure, which was a mystery for a bit, though it has yet to be verified. If so, it is a step forward.
Oh, btw, My wife isnt particularly happy with my solar obsession either  , but she loves the electricity; go figure.
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ICC
Member
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# Posted: 19 Apr 2021 23:06
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Yes, the precise reason the batteries discharged and froze is not really known and whether or not the CC still functions is a question to be answered. But it would seem the equipment selection was not proper for the conditions.
Grounding is important. The NEC calls for either the positive or negative DC conductor to be grounded (connected to the earth) which is usually the negative line, at one point.
The array components should be grounded using the special connectors that have points that penetrate the anodizing of the panel frames. #8 bare copper is normally what is used for that.
Typically an 8 foot copper clad ground rod is used. My solar designer friend told me years ago two ground rods or plates should be used as it is impossible to check the resistance of a single ground rod. Two are needed to meter the installation. The goal is to have 25 or fewer ohms resistance.
Then there is lightning protection which is a whole other topic and often neglected. Midnite Solar makes the best surge suppressors for this. They have 4 different versions. Designed and made in US with 5 year warranty that covers failure due to lightning. They have blue led's that indicate whether or not they are operating correctly. They do wear out over time as the lightning strikes they suppress deteriorate the electronic components. I have had to replace a couple over time, once within warranty. Our location has lots of summer lightning. A large direct hit may still cause equipment damage but I have not had any issues. A friend did have severe system damage from a multiple strike. That was a year before Midnite developed these SPD's.
FWIW I believe in multiple ground rods and buried plates for lightning protection, all interconnected to the array and at the house and barns which have arrestor rods and are separate from all the other grounding that is prescribed by the NEC. (My panels are distant from the buildings, so each has its own lightning protection system. I also situated my rods and plates in places I direct rainwater to in an effort to maintain wet soil for better conductivity.
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zorro
Member
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# Posted: 19 Apr 2021 23:18
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Guys
Will have a read of all this tomorrow and no doubt come back with questions as I will need to try to understand it as best I can
I do know though that I do have 2 grounding rods, both 8’ and sunk into the ground
One for the panels and one I believe for the rest of the system
Thanks again
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Brettny
Member
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# Posted: 20 Apr 2021 06:04
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Quoting: zorro If the calculations above are correct though, 3 x 340W (46.6V) panels, in series could easily exceed 150V, especially in winter? If that is the case, then I am not happy as that is the system which was soled to me!!
Yes you would be to close for comfort on the over voltage. If you find the above Info correct then running them in parallel should work. That should be as easy as installing a MC4 branch Y.
The 120v charger being plugged in and the CC tripped out or even burnt up would explain frozen batteries.
This thread is getting long...have you contacted the solar installer?
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