System Upgrade questions

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mexsudo
Forum Guru
Posts: 111
Joined: Wed Mar 13, 2019 7:40 pm
My RE system: 8 290 watt panels: Canadian Solar CS3K-290P
8 AGM 12v 115Ah batteries: Duravolt DGG115-2 (48 volt)
Inverter: Outback VFXR3648A, 3600VA
Charge Controller: Outback FLEXmax 60, FM60-150VDC
System Display and Controller: Outback MATE3s
Location: Ensenada, Baja California, Mexico

System Upgrade questions

Post by mexsudo » Tue Jul 14, 2020 12:02 pm

long story, short version:

existing equipment July 14, 2020:

Canadian Solar: 8 290 watt CS3K-290P panels
--4 strings of 2 panels
Duravolt batteries: 8 AGM 12v 115Ah DGG115-2
2 banks of 4 batteries, 48 volt
Outback VFXR3648A 3600VA Inverter
Outback FLEXmax 60 FM60-150VDC Charge Controller
Outback MATE3s System Display and Controller
Outback HUB 10.3

===
fcwlp from this forum has spent copious time assisting me via PM.
He helped me work thru several settings issues successfully. The system is now working very well.
He suggested adding 1 panel and wire the array as 3 strings of 3 panels to increase my PV harvest. He is unable to come here to do the work.

see his some of his comments and rational below.

"I have also noticed that you have 8 panels, likely wired in 4 strings of 2 panels resulting in array voltages in the mid 60s to low 70 volt range. As temperatures get hotter these voltages will drop, which may result in a poor PV harvest. The problem is with is called the IV (current - voltage) curve of the panels. You want to be operating on the flat portion of this curve versus the steep portion where there is a dramatic difference in power output.
-
Is there a possibility of adding one more panel? This would allow wiring the array as 3 strings of 3 panels which will boost the array voltage to a good level. I have had to do this with several of my predecessor's designs as he was used to doing 24V systems where two panels in series is a good choice."
===

I reached out to Outback Sales for references here in Baja California, Mexico.
My email was forwarded to a local installer.

I received a huge PDF proposal. selected Text and his images as follows
============
Solar panel upgrade for off grid installation. The project includes:
-Supply and installation of four JA Solar 345 Watts solar panels.
Spec: polycrystalline, 72 half-cells, UL listed, Marine rated.
-Supply and installation of aluminium and stainless steel rack to install 4 solar panels in the roof.
- Supply and installation of solar wire and MC4 connectors.
- Includes all accesories to make the installation.

=
Solar panel compatibility

Canadian Solar JA Solar
Power (W) 290 W 345 W
Cells 60 half cells 72 half cells
Current MPP 8.98 A 9.02 A
Voltage MPP 32.3 V 38.25 V
Voltage OC 38.9 V 46.07 V
Watts / Cell 2.42 W 2.40 W
=
Current instalation
-Four strings of two 60 half-cells solar panels which is not properly optimized for a 48V battery bank.

Upgrade proposal
- 4 series of 290+290+345w
- The solar panels are rated at different power and they are different brand but the design is compatible ant they will work at maximum efficiency.
- The string 4 should be installed according to the wood substricture, so it will have a +40o orientation.

=
JAP 72S10 345/SC

existing
existing.png
proposed
proposed.png
============
cost seems kinda reasonable.

I question the 40 degree Rotation of the new panels.
Existing panels Face due South, inclination matches solstice sun angle.

The metal roof structure is Very stout, 2x6 rafters at 24" and 2x4 purlins at 24".
There is no real need to spin them.

suggestions please!
Peter


*my system with photos for reference: http://outbackpower.com/forum/viewtopic ... 24&t=14010
peter ehlert (mexsudo)

provo
Forum Czar
Posts: 533
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Location: Sierra foothills

Re: System Upgrade questions

Post by provo » Tue Jul 14, 2020 1:20 pm

mexsudo wrote:
Tue Jul 14, 2020 12:02 pm

Upgrade proposal
- 4 series of 290+290+345w
- The solar panels are rated at different power and they are different brand but the design is compatible ant they will work at maximum efficiency.
- The string 4 should be installed according to the wood substricture, so it will have a +40o orientation.



I question the 40 degree Rotation of the new panels.
Existing panels Face due South, inclination matches solstice sun angle.

The metal roof structure is Very stout, 2x6 rafters at 24" and 2x4 purlins at 24".
There is no real need to spin them.
Here's the result of a 40° azimuth error at noon on the summer solstice in Ensenada:

Ensenada 40° az error.jpg

This little spreadsheet tells you the angle between the panel perpendicular and the sun vector. 7° isn't much -- of course, at other times and seasons the error may be more.

raysun
Forum Emperor
Posts: 3020
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: System Upgrade questions

Post by raysun » Tue Jul 14, 2020 1:43 pm

The 3645W aggregate array wattage is somewhat over the maximum rated for the FM60. (3645W / 50V = 72A)

While the negative power coefficient above STC, and a warm climate will mitigate the issue to a good degree, it does leave open the possibility of equipment damage and does void the FM60's warranty.

One operational consideration is the oversized array will make the FM60's cooling fan run a good deal of the time. Fans are the #1 component to fail. You DO NOT want to go through the considerable hassle of replacing the very inconveniently placed fan in the FM60.

I'd suggest upgrading to an FM80 (drop in replacement) and sell the FM60.

fcwlp
Forum Czar
Posts: 544
Joined: Wed Jan 22, 2020 9:40 am
My RE system: GS8048A, FM80 w/3,600 W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed
I also install and maintain grid-tied and off-grid systems, details will be given for these system if required
Location: 80 miles NE of Phoenix at 5500'

Re: System Upgrade questions

Post by fcwlp » Tue Jul 14, 2020 4:25 pm

Hi Peter, sorry I can not make it to Ensenada.

I would follow raysun's advice and replace the FM60 with an FM80 for this upgrade.

I would prefer to see all the panels with the same orientation to optimize the CC's MPPT. I understand the installer's concern on following the rafter orientation. If the rafters are exposed, sleeper blocks could be placed between the rafters for the mounts to attach to.

User avatar
mexsudo
Forum Guru
Posts: 111
Joined: Wed Mar 13, 2019 7:40 pm
My RE system: 8 290 watt panels: Canadian Solar CS3K-290P
8 AGM 12v 115Ah batteries: Duravolt DGG115-2 (48 volt)
Inverter: Outback VFXR3648A, 3600VA
Charge Controller: Outback FLEXmax 60, FM60-150VDC
System Display and Controller: Outback MATE3s
Location: Ensenada, Baja California, Mexico

Re: System Upgrade questions

Post by mexsudo » Tue Jul 14, 2020 8:06 pm

Thanks all.
I think I will go with getting a FM80.

I see them on Amazon for ~$444 USD delivered to my US mail box. it seems a Road Trip is coming up.

The rafter/purlin situation gives me all the options I desire for proper panel orientation
2020-07-14 11.30.02a.jpg
peter ehlert (mexsudo)

raysun
Forum Emperor
Posts: 3020
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: System Upgrade questions

Post by raysun » Tue Jul 14, 2020 11:20 pm

mexsudo wrote:
Tue Jul 14, 2020 8:06 pm
Thanks all.
I think I will go with getting a FM80.

I see them on Amazon for ~$444 USD delivered to my US mail box. it seems a Road Trip is coming up.

The rafter/purlin situation gives me all the options I desire for proper panel orientation

2020-07-14 11.30.02a.jpg
That's a good price on the FM80. You will want to make sure your PV disconnect is at least 60A for a 6Ga feed from the combiner, and the Charge Controller disconnect is 80A. Not sure what's in circuit right now but this is the OB 80A GFDI for ground fault protection from PV panels, through CC, to battery. https://www.solar-electric.com/outback- ... ector.html

pss
Forum Czar
Posts: 636
Joined: Mon Jul 24, 2017 8:40 am
My RE system: 8330 watts in three strings, Flexmax 60 x 3, Radian 8048A, GSLC load center, Mate 3S, Hub 10.3, FN-DC and 900 Amp, 48V Trojan T105-RE battery bank.

Re: System Upgrade questions

Post by pss » Wed Jul 15, 2020 7:28 am

If you can make it from Baja to San Diego, you can easily purchase Q-cell 295 watt panels for under $200 here. probably a better match. Just look on craig's list. Also, solar distributors will sell to public here, like giant toy stores for solar. I would use the larger panels from the quote. I wouldn't waste time upping the charge controller. Just find a 280-300 watt panel, 60-72 cell. Should be easy. I have mixed panels from 235-245 and no problems in performance to get 3 in series. The forum helpers are correct about putting three in series though.

raysun
Forum Emperor
Posts: 3020
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: System Upgrade questions

Post by raysun » Wed Jul 15, 2020 9:56 am

pss wrote:
Wed Jul 15, 2020 7:28 am
The forum helpers are correct about putting three in series though.
Correct in what way?

Since the system is in a warm climate, there's little issue with cold-weather effects, so 3 panels in series will not likely exceed the 150V maximum input of the charge controller. Cloud-edge effects may be another story.

The charge controller only needs 1.5V above the battery voltage to produce charging current. Buck converters lose efficiency as the delta between input voltage and output voltage rises. They also operate at a lower duty cycle.

It was mentioned the panels operate most ideally near the top of their IV curve, but is that not internal to the panel, not measured at the poles of the string?

IMO, the main benefit of strings of 3 v s. strings of 2 is less I^2•R loss in transmission from the roof to the charge controller. Is that a big factor here? 10ga wiring is not going to be particularly lossy with the panels being used. Wiring costs are lowered by the longer strings, but it doesn't look like that's a big issue either.

Is there something I'm missing?

fcwlp
Forum Czar
Posts: 544
Joined: Wed Jan 22, 2020 9:40 am
My RE system: GS8048A, FM80 w/3,600 W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed
I also install and maintain grid-tied and off-grid systems, details will be given for these system if required
Location: 80 miles NE of Phoenix at 5500'

Re: System Upgrade questions

Post by fcwlp » Wed Jul 15, 2020 11:39 am

raysun wrote:
Wed Jul 15, 2020 9:56 am
It was mentioned the panels operate most ideally near the top of their IV curve, but is that not internal to the panel, not measured at the poles of the string?
The MPPT function on the CC is going to try to find the optimal power, which is of course the current (i) times the voltage (V). With most 60 cell panels, when only two are in series on a hot day the panels are operating on the steep part of the I-V curve, in other words at a lower than optimal current. Therefore a lower power output for the string.

pss
Forum Czar
Posts: 636
Joined: Mon Jul 24, 2017 8:40 am
My RE system: 8330 watts in three strings, Flexmax 60 x 3, Radian 8048A, GSLC load center, Mate 3S, Hub 10.3, FN-DC and 900 Amp, 48V Trojan T105-RE battery bank.

Re: System Upgrade questions

Post by pss » Wed Jul 15, 2020 12:03 pm

Ah weedhopper's of the forum. Back in my past, I had three arrays. Array 1 and 2 each consisted of 340 watt mono panels in a 4 x 2 arrangement into my combiner box. My third array consisted of 5 235 watt and 5 240 watt polycrystalline panels in a 5 x 2 arrangement into my combiner box. My system is 48 volt. I am where the sun always shines and the ambient temps can reach 114. Needless to say, as I have previously written, panel surface temps were in excess of 145 degrees. Needless to say, panel Voc is decreased. On a 48 volt system, using an mppt controller, it is nice to have the input voltage at least 64 volts and preferably over 70. This will allow the proprietary algorithm of the charge controller to work its hidden magic and optimize amps over voltage. Even today, on a day where it is ambient 92 and sunny, my 4 x 2 arrays have a Voc of 80.2 at noon. But, until I changed my third array, the summertime Voc would be between 55 and 62 on a hot day. There was literally nothing the mppt controller could do to push my charged voltage up to 58.6. So, after 2 years, I sought out 2 panels, matching as closely as I could to my original 10 panels (i woulnd up with 245 watt panels x 2). I reconfigured into a 3 x 4 string arrangement of 12 panels. Today, my Voc is 100.2 and my charge controller is in heaven, like it's enjoying halibut, king crab and lobster every day! Now, I never have to worry about the Voc being too high in the winter because the coldest sunny day I experience is about 55 degrees ( and our Baja friend doesn't have to worry either) and the panel surface temperature is above that. As for cloud effects, not a problem as even when my system wattage exceeds that on the name plates, the amperage flowing into my charge controllers is not exceeded and the Voc doesn't get over 150 on the 3 x 4 array. In fact, my lifetime maximum Voc is 116.4 while it is 86.8 on the other two arrays.

So as I commented, it is wise for our seeker of truth to either replace his array with larger, higher Voc panels 2 in series, or to simply add panels of nearly identical wattage and I'm certain if he look, he can find 290 watt panels readily available.

raysun
Forum Emperor
Posts: 3020
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: System Upgrade questions

Post by raysun » Wed Jul 15, 2020 12:22 pm

fcwlp wrote:
Wed Jul 15, 2020 11:39 am
raysun wrote:
Wed Jul 15, 2020 9:56 am
It was mentioned the panels operate most ideally near the top of their IV curve, but is that not internal to the panel, not measured at the poles of the string?
The MPPT function on the CC is going to try to find the optimal power, which is of course the current (i) times the voltage (V). With most 60 cell panels, when only two are in series on a hot day the panels are operating on the steep part of the I-V curve, in other words at a lower than optimal current. Therefore a lower power output for the string.
OK. Makes sense.

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