Adding panels to existing system / combiner problems.

Discussion about the Power System PV Combiner (PSPV)

Moderators: OutBack Moderator Team, OutBack

Post Reply
marckeez
Forum Member
Posts: 12
Joined: Thu Jun 11, 2020 7:51 am
My RE system: VFXR3648A with a Flex Max 80 Mate 3s, FlexNet DC, all came pre-wired from Wholesale solar. Batteries are Fullriver 6 VDC in a 48 VDC bank. Solar panels are Astronegy 280watt and have a total of 12 for 3360 total watts using a Outback combiner with Rapid shut-down UL1741.

Adding panels to existing system / combiner problems.

Post by marckeez »

Having an issue adding more panels to my system. I want to maximize my system. I have a VFXR 3648A-01 with a ICP plus combiner that currently has 4 PV strings: 3360 Watts. Want to go to 4000Watts.

Original PV string:

PV STRINGS
3 MODULES
PMAX 840 WATTS
VMPP 93.60 VDC
VOC 116.07 VDC
IMPP 8.99 ADC
ISC 9.59 ADC

Original PV modules:

VMPP 31.20 VDC
VOC 38.69 VDC
IMPP 8.99 ADC
ISC 9.59 ADC

I purchased 2 new panels with similar ratings as my existing panels but higher wattage. When putting them in series it only gives me VOC of 74 VDC. Other PV string is at 116 VDC. Can I integrate these into my combiner? If so how. I did connect them to a open fuse port but it did not seem to add additional power to my system. I'm thinking the new PV string input voltage must match the other (existing) panels input voltage into the combiner??

Another Question: On the combiner fuse ports it says 32Amp. I currently have 15 Amp fuses in. Can I put a larger fuse in the port? Please help.
raysun
Forum Overlord
Posts: 11402
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Adding panels to existing system / combiner problems.

Post by raysun »

I'm thinking the new PV string input voltage must match the other (existing) panels input voltage into the combiner??
Yes. The charge controller's MPPT algorithm is going to be confused by the voltage disparity between the strings. Adding a 3rd panel to the 5th string would improve the situation, but runs afoul of the controller's maximum power rating.
One possible "saving grace" may be the actual performance of the existing array. The specifications claim 3360W, but has it actually reached (or exceeded) that value? The Lifetime Maximum Watts can be seen in the FM80 STATS menu, or in OpticsRE. What's logged?
Screenshot_20240120_065505_Drive.jpg
Screenshot_20240120_064715_Chrome.jpg
On the combiner fuse ports it says 32Amp. I currently have 15 Amp fuses in. Can I put a larger fuse in the port?
The fuses are to protect the wiring from overload. If the string feed cables have sufficient ampacity, larger fuses could be installed.
marckeez
Forum Member
Posts: 12
Joined: Thu Jun 11, 2020 7:51 am
My RE system: VFXR3648A with a Flex Max 80 Mate 3s, FlexNet DC, all came pre-wired from Wholesale solar. Batteries are Fullriver 6 VDC in a 48 VDC bank. Solar panels are Astronegy 280watt and have a total of 12 for 3360 total watts using a Outback combiner with Rapid shut-down UL1741.

Re: Adding panels to existing system / combiner problems.

Post by marckeez »

Here are the values from OpticRE:

Lifetime kWh 2,908 kWh
Lifetime kAh 174.7 kAh
Lifetime Maximum Wattage 4,352 W
Lifetime Maximum Battery 61.4 VDC
Lifetime Maximum VOC119.3 VDC
Absorb Time00:00 HRS:MINS
Float Time00:00 HRS:MINS

Please let me know what these values mean and possible resolution to my issue.
Thanks
raysun
Forum Overlord
Posts: 11402
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Adding panels to existing system / combiner problems.

Post by raysun »

marckeez wrote: Tue Jan 23, 2024 9:12 am Here are the values from OpticRE:

Lifetime kWh 2,908 kWh
Lifetime kAh 174.7 kAh
Lifetime Maximum Wattage 4,352 W
Lifetime Maximum Battery 61.4 VDC
Lifetime Maximum VOC119.3 VDC
Absorb Time00:00 HRS:MINS
Float Time00:00 HRS:MINS

Please let me know what these values mean and possible resolution to my issue.
Thanks
The important metric here is:
Lifetime Maximum Wattage 4,352 W
This shows at some point the PV Array put out enough power to reach the maximum power input limit of the FM80 charge controller. Adding significantly to the PV Array runs the risk of overloading the charge controller, potentially causing it to fail.

The conservative approach to adding more PV capacity is to add a second charge controller. I did this on a FlexPower One panel. It's a real PITA to connect into the existing DC wiring panel as it's very cramped in there, but it can be done. Adding a small external wiring panel to accommodate the two controllers is much easier.

The alternate approach would be to connect another 3 panel string to the existing PV array / charge controller. The increased risk of controller overload can be mitigated somewhat by rewiring the controller's PV input / Battery output circuit:
https://www.outbackpower.com/downloads/ ... p_note.pdf
User avatar
SandyP
Forum Czar
Posts: 573
Joined: Tue Jun 21, 2011 4:44 am
My RE system: 8 x 190W 24V Suntech panels (4 strings of 2) July 2011
4 x 325W 24V Suntech panels (2 strings of 2) added Sept2018
Mate2
Outback FM60 MPPT (max output lowered to 55amps)
12 x 2V Hoppecke GEL 612 Ah C24 - 24V System (June 2011)
Outback VFX3024 Inverter/Charger
Victron BMV-602s
Honda 5.5kW Genset
Location: Victoria, Australia

Re: Adding panels to existing system / combiner problems.

Post by SandyP »

raysun wrote: Tue Jan 23, 2024 10:02 am ../..
This shows at some point the PV Array put out enough power to reach the maximum power input limit of the FM80 charge controller.
So is it the input or output current that is the limiting factor of the FM charge controllers?

One of their manuals states that for the FM60 any input current over 60A will be lost as the FM60 has a 60A output limit.
Yet, the OB nuisance tripping note states that the FM80 can output over 80A hence replacing the 80A output breaker with a 100A breaker will help prevent nuisance tripping.
Whilst no one wants to have the magic smoke escape, some consistency from OB as to the failure causing current limits of their FM60/80 charge controllers would be beneficial.
-------------------------
http://spwebcam.myddns.me/
raysun
Forum Overlord
Posts: 11402
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Adding panels to existing system / combiner problems.

Post by raysun »

SandyP wrote: Tue Jan 23, 2024 4:58 pm
raysun wrote: Tue Jan 23, 2024 10:02 am ../..
This shows at some point the PV Array put out enough power to reach the maximum power input limit of the FM80 charge controller.
So is it the input or output current that is the limiting factor of the FM charge controllers?

One of their manuals states that for the FM60 any input current over 60A will be lost as the FM60 has a 60A output limit.
Yet, the OB nuisance tripping note states that the FM80 can output over 80A hence replacing the 80A output breaker with a 100A breaker will help prevent nuisance tripping.
Whilst no one wants to have the magic smoke escape, some consistency from OB as to the failure causing current limits of their FM60/80 charge controllers would be beneficial.
I think the controller circuitry is pretty solid within its 150V and 60/80A limits. My supposition is: excursions above 150V are death to FETs, and should be avoided; excursions above 60/80A induce heat stress; the dynamics of a large delta in V and/or I can outstrip the microcontroller's response capabilities causing a loss of control, that in worst cases could dump raw input voltage it the controller output, or cause current surges, that hopefully trips breakers.
I think the FM Extreme could handle larger current excursions because it's microcontroller is 10× faster than the stock FlexMax.
marckeez
Forum Member
Posts: 12
Joined: Thu Jun 11, 2020 7:51 am
My RE system: VFXR3648A with a Flex Max 80 Mate 3s, FlexNet DC, all came pre-wired from Wholesale solar. Batteries are Fullriver 6 VDC in a 48 VDC bank. Solar panels are Astronegy 280watt and have a total of 12 for 3360 total watts using a Outback combiner with Rapid shut-down UL1741.

Re: Adding panels to existing system / combiner problems.

Post by marckeez »

Thanks for your replies, (I little over my head in-depth). I'm wondering if I hit that maximum when I had the 2 new panels (higher watts) connected?

At this point I'm thinking about taking one of my existing panels (280 W) from one existing PV strings and add the two new panels to it. This would boost my total system watts closer to the 4K limit.

The whole point of this project was to bring my system to maximum capacity, and mount a PV string at a different angle and out of direct snow fall (existing panels on 4/12 roof, new panels around 50 degree angle under eve for less snow but still good solar light, live in Michigan).

I didn't realize all PV string voltages needed to be around the same coming into combiner.
raysun
Forum Overlord
Posts: 11402
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Adding panels to existing system / combiner problems.

Post by raysun »

I didn't realize all PV string voltages needed to be around the same coming into combiner.
The two rules of string voltages:
• String voltages must be equal (as possible).
• String voltage must never exceed 150V.
Summing the V(oc) of each panel in the string will yield the string voltage at 75°F.
The V(oc) rises as the temperatures get colder. The highest voltage will occur on a cold, clear morning before the panels start conducting current.
Exceeding 150V will damage the controller.
At this point I'm thinking about taking one of my existing panels (280 W) from one existing PV strings and add the two new panels to it. This would boost my total system watts closer to the 4K limit.
Turning a 3 panel string into a 4 panel string?
Removing a panel with V(oc) of 38V and adding two more with a combined V(oc) around 75V will run dangerously close to the 150V limit.
provo
Forum Emperor
Posts: 1392
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: 16 Evergreen EC-120 (4 strings, total 1920W)
2 SimpliPhi 3.8-m-24V (150Ah each)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC
Honda EU3000is generator
Grid connection, no selling back
Location: Sierra foothills

Re: Adding panels to existing system / combiner problems.

Post by provo »

raysun wrote: Wed Jan 24, 2024 9:07 am Turning a 3 panel string into a 4 panel string?
Removing a panel with V(oc) of 38V and adding two more with a combined V(oc) around 75V will run dangerously close to the 150V limit.
Not to mention that you'd still have one string different from the the other three strings. If you want more power, you should just keep the four strings as you have them now and add a second charge controller for one (or more) additional string(s). Charge controllers aren't that expensive :-)
raysun
Forum Overlord
Posts: 11402
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Adding panels to existing system / combiner problems.

Post by raysun »

provo wrote: Wed Jan 24, 2024 9:23 am
raysun wrote: Wed Jan 24, 2024 9:07 am Turning a 3 panel string into a 4 panel string?
Removing a panel with V(oc) of 38V and adding two more with a combined V(oc) around 75V will run dangerously close to the 150V limit.
... If you want more power, you should just keep the four strings as you have them now and add a second charge controller for one (or more) additional string(s). Charge controllers aren't that expensive :-)
I agree with this, create a single string of 2 panels and feed its output to a 100V/20A charge controller. There's lots of cheap Chinese 20A MPPT controllers that would work for this. Put a 20A fuse between the PV string and the charge controller input, and another between the charge controller output and the battery.
The two charge controllers will operate in parallel to charge the battery. Program the new controller's Absorb Voltage a few tenths of a volt lower than the Absorb Voltage set on the FM80.
provo
Forum Emperor
Posts: 1392
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: 16 Evergreen EC-120 (4 strings, total 1920W)
2 SimpliPhi 3.8-m-24V (150Ah each)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC
Honda EU3000is generator
Grid connection, no selling back
Location: Sierra foothills

Re: Adding panels to existing system / combiner problems.

Post by provo »

raysun wrote: Wed Jan 24, 2024 9:37 am I agree with this, create a single string of 2 panels and feed its output to a 100V/20A charge controller.
Here's a possibility:

Screen Shot 2024-01-24 at 9.43.15 AM.png

Not sure about the bluetooth part ...
raysun
Forum Overlord
Posts: 11402
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Adding panels to existing system / combiner problems.

Post by raysun »

provo wrote: Wed Jan 24, 2024 9:48 am
raysun wrote: Wed Jan 24, 2024 9:37 am I agree with this, create a single string of 2 panels and feed its output to a 100V/20A charge controller.
Here's a possibility:


Screen Shot 2024-01-24 at 9.43.15 AM.png


Not sure about the bluetooth part ...
Victron's Bluetooth connection works with their VictronConnect smartphone app, which makes it easy to configure and manage the controller. It's a very good quality small controller.
marckeez
Forum Member
Posts: 12
Joined: Thu Jun 11, 2020 7:51 am
My RE system: VFXR3648A with a Flex Max 80 Mate 3s, FlexNet DC, all came pre-wired from Wholesale solar. Batteries are Fullriver 6 VDC in a 48 VDC bank. Solar panels are Astronegy 280watt and have a total of 12 for 3360 total watts using a Outback combiner with Rapid shut-down UL1741.

Re: Adding panels to existing system / combiner problems.

Post by marckeez »

So, I just went out and looked at my PV connection & battery connection on the FM80. I can easily add another 20A circuit breaker in an open slot. Question is: Do I just connect this new PV string controller output to the 2 battery cable connections in parallel with existing connection inside the FM80? Another way to say it: Directly onto the two large gauge battery terminals inside FM80?
Thanks again.
raysun
Forum Overlord
Posts: 11402
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Adding panels to existing system / combiner problems.

Post by raysun »

marckeez wrote: Wed Feb 07, 2024 9:03 am So, I just went out and looked at my PV connection & battery connection on the FM80. I can easily add another 20A circuit breaker in an open slot. Question is: Do I just connect this new PV string controller output to the 2 battery cable connections in parallel with existing connection inside the FM80? Another way to say it: Directly onto the two large gauge battery terminals inside FM80?
Thanks again.
The new controller's Bat+ terminal should be connected to its own DC circuit breaker of proper amperage (20A?) The output side of that circuit breaker should be wired to the Battery Positive bus.
The controller's Bat- terminal should be wired to the Battery Negative bus.
Also, the PV + terminal of the new charge controller should be connected to the new PV array + through an appropriately sized (20?) DC circuit breaker.
Post Reply