48 panels, 225 volts, need a reliable system

[joesmith123]

48 panels total, 6 series, then 8 set of those in parallel

Each one is producing 225 volts, 10-15 amps max during peak daylight

I had only 6 sets running, and it fried a sungoldpower 6000 watt all in one unit

Now, I need advice on system that will handle and work reliably



Here is one idea where there is a midnite solar charge controller, and a big inverter that is GOOD brand (repairable)

Let me know if this diagram is going to be reliable, and let me know what inverter to use coming off the 48 volt battery system. The charge controller is gonna be a beefy midnite solar that is repairable. I'll look through and figure out the exact unit.

Also, for running air conditioning, I do see direct current AC units, is this possible? I will illustrate in this diagram:







In this diagram, I would be running 48 volt Air conditioning system WITHOUT inverter, ONLY charge controller

Is this possible?

I want a reliable setup, I want to get away from weak points, I want to run air conditioning without inverter

Theoretical question:

if they made an Air conditioner that runs on 225 volts direct current, is it possible to hook up the solar panels directly to the air conditioner and it will run properly?

I am having to understand more complex solar systems because there is too much solar power being created, critique these concepts, I would be grateful

Another thing: I need to build a simple combiner box, all the ones on amazon burn up

I do not see veterans using cheap stuff, they customize all the connections and get rid of weak points

My suspicion: Its good to separate the charging and the inverting since both those processes create high heat, and having them in an all in one system, causes too much stress...



Midnite solar classic 250-SL: Is this unit the correct one for this application? My understanding:

It has an output of 63 amps. Does that mean that it can only collect 63 amps worth of solar and inject that into batteries?

The inverter still works on the sungoldpower 6000 watt, just the charging is not working,

could I get a charge controller and use that to charge the batteries, and run 240 VAC from the sungold power inverter to power home?

https://a.co/d/6DDDQpM

This unit here, midnite solar barcelona, would be the unit to handle this system, correct?

Up to 600 volt input solar, can handle putting 200 amps into 48 volt battery system


thank you

 

[sunshine_eggo]

It would seem possible if the 48V A/C unit can work on the 42-58VDC range that a battery might experience.

63A is max on a 24V system. Lower @ 48V and lower @ higher PV Voltage:



I would assume you'll get about 53A meaning 53A * ~58V = ~3100W per Classic 250.

 

[joesmith123]

It would seem possible if the 48V A/C unit can work on the 42-58VDC range that a battery might experience.

Yes I will look up those 48 volt ac units

Solar & DC Air Conditioners | 48v DC Solar & Telecom Air Conditioner Heat Pump | Off-Grid Air Conditioning

here's one they claim run directly off of solar panels

63A is max on a 24V system. Lower @ 48V and lower @ higher PV Voltage:

Ok yes, I am studying your response. That midnite charge controller can handle about 3000 watts of solar coming in? And it can handle the voltage in my system, 225 volts?

I might get that one for now, and just run half the panels

Another big thing I need to figure out, the combiner box situation

The ones offered on amazon cannot handle the power my panels are making

420 ohms said i can build my own combiner box, can yall help me build a combiner box using stuff i can get at home depot?

I need breakers that are not cheap, with good metal

Diagram:



In this diagram we put the positive from the PV onto a high voltage breaker on a din rail

Is the breaker all you need to not let the power from all panels to short out the wires? Does a breaker allow electricity to only flow one way?

Then run Big wire from din rail to PV input (forgot to put in the big negative wire coming off the negative bus bar)

Can I just build it simple like this diagram? In my system, it would be eight 20 or 30 amp breakers handling big voltage

Someone please link me the exact breaker that would work for this situation

The ones I saw that take high voltage are $50 a piece from midnite solar

But let me know of a setup that would maybe be cheaper,

What box can I use to start the build? And which exact breakers will handle 225 volt direct current?



Ok here are Midnite solar, direct current breakers

Which one will work for 225 volt solar system? If it says 300 volts, that means it can handle up to 300 volts?

 

[sunshine_eggo]

Yes I will look up those 48 volt ac units

Solar & DC Air Conditioners | 48v DC Solar & Telecom Air Conditioner Heat Pump | Off-Grid Air Conditioning

https://www.hotspotenergy.com/DC-air-conditioner/Specs-DC48.pdf

46-59VDC

some diagrams on that sheet too

 

[joesmith123]

https://a.co/d/amQquaf

Here is midnite solar, 8 input combiner box

Can I build something similar for cheaper cost? Or is it more expensive if I get all the parts individually



MNPV8-MC4: "eight strings using included fuses up to 600 volts"

What does this mean exactly?

Which would be the proper combiner for 8 solar panel inputs running 225 volts?

 

[joesmith123]

I found a good deal on a midnite classic 150 charge controller



Here is the graph from the specs, let me know if this statement is true:

"You can put PV voltage of 225 into it but it will lessen the amount of amps it creates, but it is safe/wont burn the unit"

From what I am gathering: MPPT will accept any voltages (100-400) long as the amps are not too crazy, meaning

"I can put into this unit 225 volt strings, and it will charge up a 48 volt battery system fine"

Let me know if the statements are true, thank you

 

[Mattb4]

First off. Do not over voltage any SCC! If the SCC is rated for 150Voc this means that your panels Voc should add up to less than this rating. Depending on how cold your area gets determines how much you must derate maximum SCC Voc by.

You state you have 225vDC from solar. What is the panels actual Voc rating? What is the Vmp, Isc, Imp?

Understanding specifications will allow you to properly design a working setup.

Do not buy anything until you know it will do what you need it to do.

 

[joesmith123]

Specs of the panels


48 panels total
6 panels in series producing 225 volts
8 sets of panels

First off. Do not over voltage any SCC! If the SCC is rated for 150Voc this means that your panels Voc should add up to less than this rating

Yes I am comprehending, meaning:

Get the proper charge controller for the voltage your panels are putting out,

The charge controller voltage should be more than the voltage your panels are putting out

Sounds like the classic 250 will work for this application

But, if I did want a classic 150 charge controller to work, I can put less solar panels in series to lower the voltage

That would be a ton of work to go and dig up all the wiring on a hot roof

I did find some really good deals on classic charge controllers, but I dont know which way to go yet

I did figure out:

MNPV8 (HV)-disco3R



Ok here is a picture of the combiner box that works for this system

Midnite solar: "This box will handle 4 of my strings, and will handle up to 1000 volts"

Do you see how it has 8 breakers? Why cant we just put each positive into those breakers from each set of solar panels?

When I was doing research: If I did get those components individually, it would be very expensive

This combiner box will work for half the current solar system, it is a high voltage combiner box, and I did find one used and got a good deal, it is on the way

Let me know if I made a mistake in getting this combiner box, but from what I am gathering:

"It would be six to seven hundred dollars in parts if I was going to build a combiner box that will handle high voltage electricity since those breakers are expensive and I would need many of them"

Also MNPV8 HV disco 3R: this combiner box, can I plug in all 8 sets of solar panels into it? Or can this combiner box only handle 4 sets? Midnite solar technical support said this box will only be able to handle half the solar power of my system.

Current plan:

Hook up 4 out of 8 sets of panels into the combiner box

Get a proper voltage charge controller

I'm tempted to: take apart one set of panels, reconfigure them to lower the voltage to accommodate a midnite solar classic for the sake of at least having some electricity

It would be the cheapest route, but I dont want to do that if later on I have to reconfigure them to have higher voltage

I'll figure it out

 

[joesmith123]

Here are the specs of the midnite classic 250 charge controller and I did find a good deal on a used one



If I got this unit, it should be able to run 2 or 3 sets of panels depending on how much power they generate?

Then later on: I can get another one of these units and add it on to this system

If this thing can pump sixty something amps into the battery bank, that is plenty for now

It would be the cheapest route to get electricity again (running generator is expensive) (assuming the Chinese inverter can still invert)

And it wouldn't be a waste of money since:

"Later on, you can just get another one of these, and add it onto the system"

Let me know yalls thoughts

"Even if the chinese inverter is totally cooked, I can then start to search for a midnite solar inverter, and it would not make purchasing the charge controller a waste" (my thoughts)

 

[Mattb4]

You propose 6S8P
43.2 Voc X 6 panels in Series =259.2Voc A 250 Voc rated SCC is likely to go pfft.
8 strings of 6 panels in parallel with Imp of 4.9a = 39.2 amps This is what your wires, fuses combiner box must be able to handle at minimum.

Voltage of panels adds in Series, the current stays the same.
Current of panels adds in parallel, the voltage stays the same.

So let's say you want to use the 250Voc SCC from Midnight. You can not exceed 250Voc and really should stay at least 10% below or more depending on the coldest weather your location sees.

250/43.2= 5.78 panels. or 5 panels with a Voc of 5X43.2=216Voc this is a safe amount below rated since it is ~14%.
Max PV short circuit current rating on the SCC is 62A Your panels Isc is 5.47a 62/5.47=11 strings of 5 panels You have 48 panels So 48/5=9 strings with 3 panels unused. Thus you have 5S9P

 

[joesmith123]

43.2 Voc X 6 panels in Series =259.2Voc A 250 Voc rated SCC is likely to go pfft.

The panel does say 43.2 VOC, these panels are more than ten years old, and when you read the voltage they put out in complete sunlight: around 35 volts

The midnite classic 250 says: Max PV voltage: 250 volts

When there is no draw on one set of panels: the reading on a meter says 225 volts, but

When power is being pushed into batteries from the solar panels, the voltage reading: Around 160 volts, meaning

Never does the voltage reach the limit of 250 volts

250/43.2= 5.78 panels. or 5 panels with a Voc of 5X43.2=216Voc this is a safe amount below rated since it is ~14%.
Max PV short circuit current rating on the SCC is 62A Your panels Isc is 5.47a 62/5.47=11 strings of 5 panels You have 48 panels So 48/5=9 strings with 3 panels unused. Thus you have 5S9P

yes I am with you and comprehending the math

The lazy part of me does not want to remove the panels and have to dig through the wires and change the configuration of how I wired them originally, But

We'll see, I am fixing to possibly get a midnite classic 250 tomorrow, I will experiment with it, and if I have to reconfigure the panels, then I guess I'll do 5 panels in series to lower the voltage

"The lines on the graph represent the Classic output current at different Max Power Points Voltage (not VOC). To estimate the MaxPower Point of your system; first you have to find out the VOC of the Photovoltaic strings connected to the Classic. For example If5 Modules in series in one string and STC VOC rating is 36.6V, then the VOC of the string equals: 5(modules) * 36.6v(STC VOC) =183V.The rule of thumb says that the MPP will be around 80% of the string's VOC; 183v * 0.8 = 146.4v"

I pulled this from the midnite solar classic paperwork, in my case:

each string voc: 43.2 times 6 = 259 volts

259 volts times 80% = 207 volts

6 panels in series will produce an MPP of 207 volts

I think it should be fine for the unit, but we'll see what happens

 

[rodrick]

You most likely fried your sungold unit with over voltage
When you set up your scc voltage is a hard limit never to be exceeded EVER and make sure to do a temperature adjustment to your figures to get a accurate voltage calculation

 

[Quattrohead]

EG4 6000xp will allow you to run 12 panels in series if you're in a warm area or 11 in series if you're up north, all in one unit super surge capacity and current connected have them in stock.
Kiss

 

[Mattb4]

The panel does say 43.2 VOC, these panels are more than ten years old, and when you read the voltage they put out in complete sunlight: around 35 volts

...

Getting only 35Voc from a 43.2Voc panel in good sunlight would indicate a problem with panel or how the reading was obtained. Relying on this reading to protect any SCC you buy is your choice but understand the risk.

 

[joesmith123]

You most likely fried your sungold unit with over voltage

List of things that could have fried it: 24 panels producing serious electricity, using it like you were living on grid for a year (running big AC units), the inverter was even used to create hot water with electric hot water heater, big mistake, running air compressors, saws, big water pump

There was times it would producing 3.5 KW from solar, and it would be putting out 2K for Air conditioning/fridges/air compressors

The operating voltage of the MPPT system of the Chinese inverter (not exact numbers but close to): 100-400 volts

Meaning, the Chinese inverter can take a wide range of voltages

I honestly cannot believe it lasted that long with that dinky connection, and that tiny MPPT board

I never let it take in more than 60 amps intentionally, and I never ran all 48 solar panels into it

My new methods will be more natural, for example: Run less Air conditioning, run less fridges, look into 48 volt direct current air conditioners to lessen the load of the inverting

I would honestly not run more than 10 solar panels on the all in one Chinese inverters, and not push 2KW input from solar, or output into alternative current

Getting only 35Voc from a 43.2Voc panel in good sunlight would indicate a problem with panel

Panels brand new, fully clean, will put out the open circuit voltage that is claimed or close to it

After years of the sun murdering the panel, the weakening of the panel lowers the open circuit voltage

Yes, if these panels were brand new and not 15 years old, they would be putting out closer to 43.2 open circuit voltage

EG4 6000xp will allow you to run 12 panels in series if you're in a warm area or 11 in series if you're up north, all in one unit super surge capacity and current connected have them in stock.
Kiss

Yes, I would not run more than 12 panels into the chinese inverters, if they claim 6000 watts, do not run them at more than 1/3 the wattage

I dont care if the thing weighs 300 pounds, and claims 15KW, the connection where it matters, will be weak, do not push them



Also I did get a service manual for it from the manufacturer, it has detailed instructions and pictures of taking these things apart,

The file is 28 megabytes, too big for this app, but here is one picture from it

 

[Mattb4]

Yes I will look up those 48 volt ac units

Solar & DC Air Conditioners | 48v DC Solar & Telecom Air Conditioner Heat Pump | Off-Grid Air Conditioning

here's one they claim run directly off of solar panels


Ok yes, I am studying your response. That midnite charge controller can handle about 3000 watts of solar coming in? And it can handle the voltage in my system, 225 volts?

I might get that one for now, and just run half the panels

Another big thing I need to figure out, the combiner box situation

The ones offered on amazon cannot handle the power my panels are making

420 ohms said i can build my own combiner box, can yall help me build a combiner box using stuff i can get at home depot?

I need breakers that are not cheap, with good metal

Diagram:



In this diagram we put the positive from the PV onto a high voltage breaker on a din rail

Is the breaker all you need to not let the power from all panels to short out the wires? Does a breaker allow electricity to only flow one way?

Then run Big wire from din rail to PV input (forgot to put in the big negative wire coming off the negative bus bar)

Can I just build it simple like this diagram? In my system, it would be eight 20 or 30 amp breakers handling big voltage

Someone please link me the exact breaker that would work for this situation

The ones I saw that take high voltage are $50 a piece from midnite solar

But let me know of a setup that would maybe be cheaper,

What box can I use to start the build? And which exact breakers will handle 225 volt direct current?



Ok here are Midnite solar, direct current breakers

Which one will work for 225 volt solar system? If it says 300 volts, that means it can handle up to 300 volts?

Trying to answer a few of the many questions here. You should not typically burn up a combiner box even the less expensive ones from Amazon. Failure is often a case of improperly connected items. You do have to be within the ratings for components (and with Chinese made components it is best to de-rate a bit).

Take your example of a string of panels: The voltage is ~250Voc with current of the string being ~5a. All the items to bring that to your combiner box needs to be able to handle that. In the combiner box will be a cutoff breaker for that string or a fuse for that string. Typically they use the panels fuse rating which is 10a in your case. In the combiner is a number of strings being placed in parallel. The voltage does not rise but the current adds up. So 5a from 1-8 =40a being fed to the output to SCC breaker. That breaker is likely going to be at least 40a (often 63a for din rail) and the associated wires or busbars it gets power to and leaving must be sufficient for that 250vDC at 40a.

So you want to build your own? Easy enough if you simply follow the specs for the components.

 

[joesmith123]

Got the midnite classic 250

Trying to answer a few of the many questions here. You should not typically burn up a combiner box even the less expensive ones from Amazon. Failure is often a case of improperly connected items. You do have to be within the ratings for components (and with Chinese made components it is best to de-rate a bit).

Yes, I tell you what happened:

When the chinese inverter was burning out, thats when it burned out the chinese combiner box, meaning,

The problem with the Chinese inverter caused the combiner box to burn up, the main breaker




To fix the Chinese combiner box, just for that one breaker alone, is I am guessing $100, meaning,

eventually, you need to just toss the whole thing out and start with reliable and serviceable products

Chinese combiner box: What I notice, any kind of high voltage direct current breakers are expensive, there's zero chance amazon is gonna bring you a STRONG combiner box for $150

So you want to build your own? Easy enough if you simply follow the specs for the components.

I tell you what happened when I went down this narrative:


To get the individual breakers, the big box that holds them, all the connections inside, the random this and that, if you wanted to build it yourself, it would cost minimum $1000 plus days of labor

The route we are taking: Talked to midnite solar, told them the panels and voltage, they said

MNPV8 HV will handle that system and those strings

got one used, 10 plus years old, but beefy, picture of the exact one:





Here are pictures of the inside of the exact item that will be installed on this system

Show me one thing on amazon that handle 1000 volts direct current for less than $1200...

A unit like this new with of the added features, and all the little things, would be $1500-$2000

And I would bet that the components are not as good as older units, thicker steel, better conductors

Its on the way, should be here Saturday

Current plan:

Rig up classic 250: hook up one set of 200 volt panels into the pv input, run battery wires to the 48 volt system

If the chinese inverter can still invert (it worked fine after I cleaned the terminals with wire wheel on dremel, I even ran an air compressor fine), then

The system should work, albeit not at its peak of course, but the panels should feed the midnite solar, the midnite solar will pump into the 48 volt system, the 48 volt system will pump into the chinese inverter, chinese inverter should put out 240 VAC...

I go now hook it up

 

[Mattb4]

Heck of a nice Combiner! Yes a new one of that quality would not be inexpensive and to build one of that quality (if you could find the components) would also not be cheap. Looks like you scored.

Hopefully the Inverter portion of the AIO continues to work. Keep it clean.

 

[joesmith123]

Inside of midnite classic 250, very complicated



hooked up midnite solar classic temporarily, ground, plus minus of battery, plus minus of pv



Checked the pv voltage and made sure it was correct before turning on midnite solar, input pv voltage: 219



Turned the midnite solar on, hit enter confirm solar and 48 volt system

Machine turned on, mpp voltage showing 158...



While midnite solar is charging, mpp voltage: 162



Once midnite solar charge controller was on and functioning, I go turn on the chinese inverter...

Fault code 9: bus start failure



This is from the manual. Chinese inverter has been doing this on and off. I hit the burned terminals with wire wheel and it worked. Now it is doing this fault again

I am exhausted of dealing with the chinese inverter, she's finished

The only way to fix chinese inverter: disassemble completely, conduct tests shown in the service manual, put in the new main board, etc, it would be a complete rebuild

Next step: remove Chinese inverter, work on the area, close up batteries from elements mount the midnite solar somewhere dry and cool, figure out whether I will be installing the new board on the chinese inverter myself, open up the door to getting a proper inverter

What is the old series midnite solar inverter that works well with a classic 250?

 

[Mattb4]

Your Midnite SCC seems to be working from the images showing 9.1 amps and 425w going to the battery so I guess it something else that is not working. Your AIO shows error 9. Check your manual to see what that signifies.

 

[joesmith123]

yall see how they have midnite solar charge controller connected to the huge serviceable inverter

Where can I get one like that, without all the bells/whistles/useless junk that I just toss or dont use, meaning

I want to open the door up to robust electronics, reliable

Point me in the direction of:

An inverter that would take in 48 volts from big battery bank, and turn it into 240 VAC

Look at the picture, if something burns up, you do not have to lose $1500 like I did with the chinese inverter, meaning

If I can only buy the components that I need that are reliable, then it would lessen the overall cost

I dont need more than 2000 watts, I am simply wanting the component that is fixable

Basically: what is the inverter that will work will take 48 vdc -> 240 VAC reliably, with ability to fix it

I do see midnite solar selling separate components, OK yes, which ones do I need to invert?



I do see people coupling the midnite classic charge controllers with this magnasine ms4448

Are these american made? Are they fixable?

 

[joesmith123]

Ok here is the combiner box that I will be using and I already ordered

Now, another person from midnite said: this is a grid tie combiner box

The other midnite solar person said: this one will work for my system (off grid)

What about this combiner box makes it "grid tie"? I dont see anything about using alternating current

I am at the point where I am fixing to start taking inverters apart, and understanding them because:

I have a bunch of expensive components that are not being used

Powerone PVI6000 grid tie inverter, broken sungoldpower 6000 all in one inverter, broken combiner box

I will start to take them apart until I understand them

Soon I will be making a post on the "up in smoke" section where I try to make a grid tie inverter work off grid

 

[Mattb4]

The combiner box you now picture is a fairly simple 8 string with fuse protection per string. I see nothing else in it like SPD or SCC disconnect breaker. Not all that impressive. I suppose it could be used in either a grid tie or off grid setup. All it does it bring in the 8 strings, provide fusing, parallel them and have bus bar connection lugs.

Nothing wrong with attempting to understand your components but taking things apart can result in breaking things. This even more so when the theory of how they all work together is lacking. Perhaps before you go further you could first spend some time learning all that you can. I mentioned before it makes no sense to spend big money on something and than hobble it by not properly setting it up.

Typically you can not make a grid tie inverter setup work off grid. There are methods to do so but it requires more (expensive) equipment and knowledge.

I wish you luck but I think I have helped all that I can.

 

[joesmith123]

Plan with the sungoldpower 6000: setup an organized area and take it apart, fix the problem, put it back together only for the:

48 volt DC ->240 VAC

it would NOT be doing any of its MPPT functions, since MPPT charging is done by midnite solar

I would put the Chinese inverter back together omitting all the extra functions that are not going to be used

Somehow: take it apart, understand the major components and how they connect, salvage at least the inverting abilities

If done properly, it would save the system, and make no more spending necessary

I'll figure it out, everything will be done with low amps and proper fuses, my other experimentation plan:

Typically you can not make a grid tie inverter setup work off grid. There are methods to do so but it requires more (expensive) equipment and knowledge.

Use the inverting abilities of a robust grid tie inverter by getting rid of its need to be tied to a grid...

This would be a separate system away from the 48 volt system, I would start very small, I would put maybe a few solar panels, just enough to turn it on, then do something inside of it that would allow it to put out 240 vac, and I would run something very low amperage, just for the sake of the testing, i would have things fused properly, gloves, goggles, safety

"The grid tie inverter can take PV direct current, and turn it into alternating current 240 vac, but it cannot charge a battery bank"

"Ok then, lets try putting some PV into it, trick it into inverting, and see if we can make useable 240 VAC from sunlight, skipping the 48 volt battery bank"

"This inverter setup would be for daylight use, not connected to the 48 volt battery bank"

Why did I get to this point: I have 2 expensive, robust 6000 watt inverters that are not being used and now thinking I need to spend thousands more on ANOTHER inverter, nonsense

The better route: fix what I have, understand the components using testing devices

 

[robbob2112]

Plan with the sungoldpower 6000: setup an organized area and take it apart, fix the problem, put it back together only for the:

48 volt DC ->240 VAC

it would NOT be doing any of its MPPT functions, since MPPT charging is done by midnite solar

I would put the Chinese inverter back together omitting all the extra functions that are not going to be used

Somehow: take it apart, understand the major components and how they connect, salvage at least the inverting abilities

If done properly, it would save the system, and make no more spending necessary

I'll figure it out, everything will be done with low amps and proper fuses, my other experimentation plan:




Use the inverting abilities of a robust grid tie inverter by getting rid of its need to be tied to a grid...

This would be a separate system away from the 48 volt system, I would start very small, I would put maybe a few solar panels, just enough to turn it on, then do something inside of it that would allow it to put out 240 vac, and I would run something very low amperage, just for the sake of the testing, i would have things fused properly, gloves, goggles, safety

"The grid tie inverter can take PV direct current, and turn it into alternating current 240 vac, but it cannot charge a battery bank"

"Ok then, lets try putting some PV into it, trick it into inverting, and see if we can make useable 240 VAC from sunlight, skipping the 48 volt battery bank"

"This inverter setup would be for daylight use, not connected to the 48 volt battery bank"

Why did I get to this point: I have 2 expensive, robust 6000 watt inverters that are not being used and now thinking I need to spend thousands more on ANOTHER inverter, nonsense

The better route: fix what I have, understand the components using testing devices

Typical grid-tie inverter will not output current unless it senses grid power already so it can sync up the frequency. If the inverter is capable of islanding or grid-forming itself then it can work fine as an off-grid inverter.

island == off-grid or without grid
anit-island == must have grid power to sync to in order to power up. Usually CT clamps or similar so it can tell when power is present and get the frequency of the AC and sync to it, so when it turns on it doesn't go Pft from the mismatch

You got here from doing your install before doing your design and understanding the limitations of the equipment.

So, it was mentioned several times - the colder it gets the more voltage the panels produce. Where I live it hits -10F from time to time. That would jump my panel voltage up around 15v. Assume hypothetical panel Voc of 48v. So if I string it together for 250mppt 48 * 5 = 240, but if it gets cold add the 15v and I am at 255 and my mppt goes pft in a second or so.