Outback charge controller not using all of the arrays volts

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Doin it

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Could use some help figuring this out. I have an fm60. Its supplying 3200w max sustained, array is new panels 3660w, 99.9vmp, 120voc, 36amps I observe the input voltage not going higher than 80ish volts most of the time when it should be capable of 99v. It does show 99v and higher input on the screen rarely but I think this is only when input amps are low. Also I do rarely see 3600w but its only for a few seconds. When solar should be at it peak-highest production I cant get anymore than 3200w sustained from the array.
My thoughts are that maybe the chargecontroller combines the battery voltage (16s 65.6v max) with array voltage, and will not let the input volts from array be higher than the difference between 150v (max allowable array input voltage for charge controller) and the batteries present voltage? Is this how its done by the charge controller? If it is, that could be why Im not seeing closer to the voltage that should be available from panels.. I hope this isnt correct,, 66v (2 panels in series) wasnt enough volts to charge 16s battery so I needed 3 panels in series for 99v but if I cant use all the arrays power that would be a huge bummer. 99v from array and 65.6v from battery would be 164.6v which might be why input array volts is being lowered-not accepted? When the battery is at 58ish volts then I also see higher input voltages around 100v.
 

OffGridInTheCity

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Interesting. I have Midnite Classic 150s, been operating for over 2 years now with 24 and now 45 panels (285w each)and see the same things. Mine are 3s and I'm guessing yours are too. Not sure what you expect voltage wise as the point of MPPT is to maximize power (e.g. watts), not voltage. Lower voltage is simply higher amps and vice versa. My Midnite ClassicsMPPT voltage is typically around 83-88v as you describe and (anecdotally) around90% of rated PV power per what the controllers report when things are 100% clear/sunny all day.

I *rarely*get 100% of rated panel output and (as you describe) only for short periods. I have gotten as much as 110% for short bursts. There are many factors - the time of day, weather, angle of panels (both vertical and horizontal), and *temperature*. I actually get less power (5-10% less)in the heat of summer (90-100F ambient high) as compared to coolerspring and fall (60-70F ambient high) on similar100% clear/sunny days and the days are a little longer.

I use the PVWatts website -https://pvwatts.nrel.gov/pvwatts.php- to see what I should expect and so far, I've been wellmatched with this website predictions - weather is quite variable so it can't be exact. So I've come to believe that expecting 100% of your rated array was never reasonable except for a few peaks here and there as you describe.

You might try PVWatts or similar to see what you should expect for your location, angle, etc - and view it more as a monthly/yearly metric.

Midnite Classic's offer 2 different 'main' MPPT tracking algorithms - maybe Outback does too? If so you might try some alternatives to see if it makes any difference.

Overall - I'd say your system is working in the range of 'as it should'.. but that's just an anecdotal comment based on my own experienceand I'll look forward to other comments on this :)
 

ajw22

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A couple of possible factors you're missing:
* You're measuring V-PV at the controller, whereas Vmax is at the panels. Ie you might be losing voltage in the PV cabling. The higher the current (~=power), the higher the V loss.
* May 31st, the sun is at the highest point now. If your panels are inclined towards the south (or north), they're kinda pointing in the wrong direction this time of year, thus the panels will not reach Pmax
* If you're in the north, it's probably getting hot. PV panels lose Pmax at around 0.5%/C
* Summer and little rain... panels dirty from dust, pollen, bird poo, etc?
 

Doin it

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Very good-knowledgeable comments, thanks!
So does from roughly 460w to 560w under max sound reasonable for what I would consider a full sunny day at peak sun, 70f degrees, two strings 40ft each of 10gauge wire supplying 19amps each?
Panels arent dirty, they are cleaned often and the 3200w max Im seeing is year round
Panels are facing south (I live in Tennessee) and on a 6/12 pitch roof 26 degrees
As for what voltages I expect,, Im thinking that when panels are capable of full amp output and full voltage output then I should see closer to max (3660w) from array..
can any of u verify that the combined battery voltage and input voltage on charge controllers screen from array is higher than 150v on a 150v charge controller?
How would I try a different mppt tracking algorithm? The outback has something called U-pick mppt.

Appreciate the pvwatts link.. I believe that its showing me the possible amount my array can produce if I was using all of the power. For this month pvwatts said 518kwh,,, my monitoring system tells me I only used 378kwh from array this month. Ofcourse this is due to my battery bank (once full) being to small to store all of the potential panels power
 

Redpacket

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The key point is mostly likely the specs for the panels (eg Vmp & Imp) are measured under test conditions & there's generally two of these test conditions:
- The lab special: STC "Standard Test Conditions" where the panel is at 25degC, with 1,000W/sqm light & measured quickly before the cells start to warm up.
- The more like reality: NOCT "Normal Operating Cell Temperature" where the ambient is 20degC, there's 1m/s wind & only 800W/sqm light & measured when the cells have warmed up to typically 45degC or so.
Bottom line: you typically see output from your panels of the NOCT values when the sun is at 90 degrees to the panels.
It can burst above this eg if the sun pops out from clouds in a cold clear day.
Combined with the other factors the guys above have mentioned, you get less into the controller accordingly, typical best being about 80% or so of the STC max power specs.

EDIT: I checked the specs for the FM60 here:
http://www.outbackpower.com/downloads/documents/charge_controllers/flexmax_6080/specsheet.pdf
It says "NEC Recommended Solar Maximum Array STC Nameplate" for 48V battery systems is 3000W & 60V 3750W
So it's possible depending on your battery voltage (somewhere between 48 & 60V?) you're maxing out the FM60?
 

Doin it

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My array is 3660w. I charge my battery to 65.6. Im under the 3750w and only getting 3200w sustained
Most likely its that Im getting all I can from the array due to everything mentioned above.
I would still like to know if anyone sees higher than 150v on the outbacks screen, combining battery and array input voltage.


image_hxernk.jpg
heres an example, the combined voltage is 151.4 (86.1 + 65.3) and as battery voltage drops then the input voltage from array rises on charge controllers screen, but still not going over roughly 150v combined.
Im saying that the array at time of the pic was only capable of supplying 30amps, which is reasonable for the time of day,, but Im fairly certain at the time of the pic that the array is capable of supplying higher voltage..
Is the mppt not capable of allowing more than 86.1v in from array because it cannot lower voltage that is any higher than 86.1 down to 65.3?

image_rhkfoi.jpg

This pic is showing a higher amount of volts input from panels, amps are lower because loads are lower. But just a min ago when loads were higher and more amps were needed then the volts were like the first pic
 

Redpacket

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Re adding the input & output voltages together, far as I know, that's not a done thing by the manufacturers :)
As long as each voltage (separately) is in spec, then it's fine.
It's input V x input A = Vmp x Imp from the panels, &
output V x output A = power into the batteries, which you already know.
With those 10AWG cables at 19A your voltage drop should only be about 0.4V so not too much.
https://www.rapidtables.com/calc/wire/voltage-drop-calculator.html

Did you look up the NOCT values for your panels?
Mine (larger 72 cell panels) are quite different from the STC values:
STC Vmp: 37.2V
NOCT Vmp: 34.5V so about 92% IF the conditions at my place match the NOCT ones, so note if it's hotter &/or less wind = worse (lower Vmp & Imp)....

The two screens above look like normal & expected operation to me?
It's normal that as the controller reaches your "battery full" voltage, it backs off the current to the batteries which in turn unloads the panels so the volts there rise.
The MPPT algorithm will search for the max power point & do it's best to get the most from the panels (if not close to battery full).
 

Doin it

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Red, I understand that its normal for the amps to lower when battery is full. I dont understand why the charge controller cant use 100v from array. Shouldnt the controller be able to use 100v if at the time the panels are capable of 100v?,, regardless of the amps being used from the array.. Is there a maximum amount of volts that the mppt can use depending on what battery voltage is? Even tho Im well under the 150v the controller can accept?
Somethings telling me that its not a coincidence that my battery voltage and array input voltage (on charge controllers screen) never go over roughly 150v, unless the charge controller isnt having to create more amps, then itll use over 150v combined like the second pic
 

OffGridInTheCity

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Doinit said:
Red, I understand that its normal for the amps to lower when battery is full. I dont understand why the charge controller can use 100v from array when the amps the controller is charging with are lower. Shouldnt the controller be able to use 100v if at the time the panels are capable of 100v?,, regardless of the amps being used from the array.. Is there a maximum amount of volts that the mppt can use depending on what battery voltage is? Even tho Im well under the 150v the controller
It sounds like you're focusing on voltage - but voltage, by itself, is not the issue. The issue is *power* = e.g. watts. Note that 100v * 30a = 3000w and 90v * 35a = 3150w. In this example, 90v is giving more power than 100v. The Outback MPPT algorithm is raising and lowering the voltage (and correspondingly raising and lowering the amps) every few secondsto find the maximum power point - e.g. the combination of voltage * amps that brings in the most power. A lower voltage (than panel max) will result in greater amps / power - you can trust the Outback to find the sweet spot on this.

I've seen videos explaining the 'maximum power point curve' concept - but don't remember the details. You might want to search one out to get more info. But the idea is that there is a curve of volts/amps that determinemax power (max watts from panels)that changes from moment to moment as the panel output changes from moment to moment due to clouds, temp, sun strength etc.

As a side issue - as the battery fills and it goes into absorb/float, the Outback will limit the output current to the battery.. because its in CV (constant voltage / declining amps)mode as the battery fills. Thisin turn willcause the Outback to accept less input power or shunt aside excess power - because its the output that is the overriding issue - e.g. to avoid overcharging the battery. Ultimately, if the battery reaches 100% full, the output will go to 0 and the input power will go to 0 as well... even thought the panels are still producing power.
Example from my own system on output affecting PV input power:
Midnite Classics let you set the max output amps and I had to set mine to down to 80a because at 86a (the max the controller supports) my 80a circuit breakers trip. This actually happened and I was going crazy trying to figure out what happened. This means myinput power is limited to 80a * battery-voltage which means that when my battery is low (say 50v), I can actually loose some PV input power because the input cannot exceed the 80a * 50v = 4000w output whereas my array can produce 4275 watts at 100%. As soon as my battery reaches 53.5v then 53.5 * 80 = 4280watts and I'm good to go.


This is all 'as is should be' and why you buy an expensive controller like Outback or Midnite Classic (or others)because they are quire sophisticated in getting every bit of power (e.g. watts) that it can and constantly check for the best solution.
 

Doin it

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.. Im thinking this is the issue.. the charge controller dropping my array from 100v down to roughly 86v when its trying toget max output from my array,, problem with that is my array is 100vmp and 36amps for 3660w and when the charge controller mppts the voltage at 86v (instead of 100w) and arrays producing close to its max input amps at 36amps, then charge controllers only allowing 3100w. I could understand if the controller was dropping my volts to make more amps but thats not whats happening. Its like controller will not accept voltage from the array higher than 85ish, unless battery voltage is lowered, which allows the input voltage to raise the same amount that the battery voltage drops. Or over 85v is seen in pic 2 when the controller doesnt have to create more amps than whats being input by array.

Im starting to think that the controller is only capable of raising the amps to a certain amount above what the array is inputting and it will only allow array to input enough voltage to enable the controller to raise the amps to the max amount above the input amps that the controller is capable of. The controller is capable of 60amps but it can only raise the amps by a certain amount higher than whats being input by array. This could be why I cant get closer to the 3660w I should be seeing from the array.

So basically Im thinking my array should have been closer to 90 volts instead of 100v so Im not losing the top 10ish volts from my array. 10 volts at 36 amps is 360w which is close to the 460w Im not getting from array that I should be.
Basically Id see no way to change anything in the settings to make the controller mppt at a higher voltage because the controller can only use the amount of volts needed to raise the amps by the amount it can raise the amps to.. Im saying if input amps are 30amps then the controller cant make that into 60amps, it can only use the amount of voltage needed to raise the amps by the amount it can raise the amps
 

Redpacket

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Can you please advise the NOCT Vmp & Imp values for your panels.
Or tell us the brand & model of the panels please.
You mentioned you're in Tennessee, daytime temps are ~27degC atm? Ie panels will be hotter than NOCT = LESS output & lower Vmp numbers.
 

Doin it

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image_qhvysf.jpg
.. 6 longi solar panels and 6 Canadian panel all with the same specs.. this issue isnt related to the temp outside... I get very close to the same amount of watts all year
 

not2bme

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Have you tried a different config? A 2S instead of 3S? You are still within the spec of your batteries. Assuming regular 4.2 * 14S = 58.8v. Vmp is 33V * 2 = 66V. Your MPPT controller is more efficient closer to your battery voltage. You might lose 5% efficiency going with 3S. Also efficiency also drops when you max out your MPPT contro. Probably another couple % drops. You need to look at the efficiency curve of your controller.

I did that once to test and found it was slightly better but it means thicker cable runs so I decided for more panels than more efficiency.
 

Doin it

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2s is how I had it wired when I wasnt using a 16s battery because my grid tie inverters voltage sweat spot was roughly 66v.
I had to go to 3s because 2s was not high enough above the battery voltage to charge batteries properly in the winter when its very hot., my battery voltage is 58v-65.6v. Im actually only charging to 65.1 but thats kinda irrelevant



image_ahiuho.jpg

Finally found something regarding what I was trying to say, I didnt know how to put it in the correct words.

This is saying without hyper voc that the 150v max includes the battery voltage,, so 66v battery minus 150v is 84v that the controller can use from my array.. problem is that my array is 100vmp,, controller isnt using roughly 16v that it could be using to convert to more amps..,, right around 78v-86v (depending on battery voltage) is the max constant voltage I see from my array when the controller acts like its getting all the power my panels can deliver(its not tho)... Im getting 3200w max constant from array but if the controller could use that other 16v then I would be getting real close to the max (3660) my panels are trying to give me.
This explains why as my battery voltage rises the controller uses less volts from the array,, and the other way around,,, as battery voltage falls the controller uses more volts from array.. the controller wont allow no more than roughly 150v array + battery

This is a hard lesson learned for me,, the string sizing tools told me 2s wouldnt work well (I agreed) but it didnt tell me that wiring my panels at 3s would keep me from getting max power (all of the volts) from my array :(
Now wishing I would have got the midnite 150 instead of outback 150.. but Im still wondering how many amps either controller can raise from the panels input amps to charge battery.. Im thinking its around 20amps that the controller can raise the input arrays amps. this amount would also be the amount of volts higher than battery voltage that can be ACTUALLY used at peak production.,,this means my array should be only roughly 86v to get max power from my panels when they are capable of giving me max power

Now knowing all of this I should have installed an array around 90vmp max to get very close to all the power from panels at peak harvest
 

OffGridInTheCity

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Doinit said:
2s is how I had it wired when I wasnt using a 16s battery because my grid tie inverters voltage sweat spot was roughly 66v.
I had to go to 3s because 2s was not high enough above the battery voltage to charge batteries properly in the winter when its very hot., my battery voltage is 58v-65.6v



image_ahiuho.jpg

Finally found something regarding what I was trying to say, I didnt know how to put it in the correct words.

This is saying without hyper voc that the 150v max includes the battery voltage,, so 66v battery minus 150v is 84v that the controller can use from my array.. problem is that my array is 100vmp,, controller isnt using roughly 16v that it could be using to convert to more amps..,, right around 78v-86v (depending on battery voltage) is the max constant voltage I see from my array when the controller acts like its getting all the power my panels can deliver(its not tho)... Im getting 3200w max constant from array but if the controller could use that other 16v then I would be getting real close to the max (3660) my panels are trying to give me.
This explains why as my battery voltage rises the controller uses less volts from the array,, and the other way around,,, as battery voltage falls the controller uses more volts from array.. the controller wont allow no more than 150v array + battery

This is a hard lesson learned for me,, the string sizing tools told me 2s wouldnt work well (I agreed) but it didnt tell me that wiring my panels at 3s would keep me from getting max power (all of the volts) from my array :(
Now wishing I would have got the midnite 150 instead of outback 150.. but Im still wondering how many amps either controller can raise from the panels input amps to charge battery.. Im thinking its around 20amps that the controller can raise the input arrays amps. this amount would also be the amount of volts higher than battery voltage that can be ACTUALLY used at peak production.,,this means my array should be only roughly 86v to get max power from my panels when they are capable of giving me max power

Now knowing all of this I should have installed an array around 90vmp max to get very close to all the power from panels at peak harvest


The article you list says:
>"When the Classic input voltage rises above 150v it will switch off (stop outputting power)...."
e.g. it will go into HyperVOC mode
>"...it will switch off (stop outputting power)......
e.g. power will go to 0 (0 volts, 0 amps on input and output)
>"... in HyperVOC mode the microprocessor and all other functions like AUX will continue...."
e.g. it will continue to operate rather than do a hard shutdown - except that power = 0. This is allows external controls (AUX1 and AUX2) and data logging and internet access to continue to work during this condition. And when the condition passes, the MPPT will resume making power without having to manually reboot the system.

>This is saying without hyper voc that the 150v max includes the battery voltage,, so 66v battery minus 150v is 84v that the controller can use from my array.....
Its not saying this.

Its saying that Midnite Classicshave protection against extreme weather conditions such as sever cold (as in 30 below 0 type of thing). They call thiscondition/feature"HyperVOC"- e.g. extreme cold cancausevoltages to spiketemporarily. For example,in the early sun ofa cold night it might still be 30 below 0 cause 'extra high' voltages until the sum warms things up. So rather thanshut the controller down (causing you to manually turn it back on) the HyperVOC feature kicks in and let's theinternal processor will continue to operate so that it can resume making power when the extreme condition goes away... such as maybe later in the morning when the temp goes from 30 below 0 back to 0.

This has nothing to do with 85'ish volts - MPPT - that you are seeing.
 

daromer

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3s is most likely more efficient than 2s for this controller. Most are to be honest. Being close to battery voltage is for old pwm controllers and badly designed mppt. Most buck/bost converters today have a set voltage range where they are ALOT more efficient and most of the 150ish volt is around 100-110 if im not mistaken. I have read some paper about this back in the days

So if we are going to explain why you get 85V.. Thats tricky. Because generally with perfect conditions the sweet spot is around Vmp. with that said the controller will regulte the voltage to the spot where it gets the most Power out of it. If thats 85 that may be it for this controller vs the panels. Its hard to tell without putting in another type of controller comparing wattage. NOTE that you need an external device to meassure wattage since some of the controller doesnt even have a shunt inside and interpolates the output......
 

Redpacket

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The Hyper Voc bit in the manual is about overload not normal operation & is irrelevant anyway.

OK, thanks for posting the panel details.
So I found data for the LR6-60PE-305M panels here:
http://www.en.longi-solar.com/uploads/attach/20170226/58b2d2a9aba93.pdf
The "Electrical Characteristics at NOCT" values are:
Vmp = 30.3V x 3 for your system = 90.9V at NOCT mp, less say 1V cable losses = 89.9V at the controller
Imp = 7.39A x 4 strings (of 3 in series, 12 panels right?) = 29.56A at NOCT mp
Now you need to add temperature compensation for the actual temp the cells are at (yes it's definitely relevant sorry!)
See the graph in the linked data sheet bottom left? It shows what happens with cell temp. Hotter = lower voltage = exactly what you're seeing.
Which is very close to what the FM60 is displaying.
So your controller is doing it nearly perfectly according to the NOCT & temp specs.
None of us gets the STC spec power! Wish we did but that's the way the silicon works ;-)
 

Doin it

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It says hyper voc gives u the option to go up to (PANEL VOLTAGE) the max operating voltage (150v) PLUS the battery voltage. So essentially array can be 150v plus battery voltage only while using hyper voc... without hyper voc there is no battery voltage plus 150v array,, there is only 150v array +battery combined....
I know that regardless the controller will not mppt the array higher than 86v using hyper voc or not so. Wouldnt get more power, but reason for showing this pic is to confirm that the controller wont allow more volts input from array than whats left from 150v once battery is subtracted from 150, which in my case is roughly 86v..
that sentence is saying without hyper voc (which my outback doesnt have) u do not have the option to go up to max operating voltage because u have to minus the battery voltage from the max the controller can accept...


U can still use arrays up to 150v and controller will still function but it will mppt the voltage down to whatever is left from 150v once battery voltage is subtracted from 150v..

Anybody else reading it that way?
 

Redpacket

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Doin it said:
It says hyper voc gives u the option to go up to (PANEL VOLTAGE) the max operating voltage (150v) PLUS the battery voltage. So essentially array can be 150v plus battery voltage only while using hyper voc.....
that sentence is saying without hyper voc (which my outback doesnt have) u do not have the option to go up to max operating voltage because u have to minus the battery voltage from the max the controller can accept...


U can still use arrays up to 150v and controller will still function but it will mppt the voltage down to whatever is left from 150v once battery voltage is subtracted from 150v..

Anybody else reading it that way?

Re the "hyper voc" if you go over the 150V if shuts off. It's an "over-voltage protection" feature. It doesn't help or get you more power.
Most MPPT's will only work if Vin is > Vbattery & that's what your FM60 does too.
Be happy it's working well ! :)
 

Doin it

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Im not saying hyper voc helps get more power..
Red I appreciate your research I understand getting 100 or 250w less due to certain conditions,, but Im saying theres no way I should be getting only roughly 3100w out of a 3660w array.. I believe this is happening due to the 150v charge controllers only being able to raise the charge amps by a certain amount and therefor will not accept all of the Volts from array, it will only mppt-accept voltage above battery voltage that is the same as the amount of amps it can create.. this is why 150v combined (battery+array) is all the controller can actually use..
Ofcourse the controller can use higher voltages from array when its not trying to get max power out of the panels, like my second charge controller pic shows
 
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