Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

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thundley
Forum Member
Posts: 6
Joined: Mon Oct 19, 2020 11:01 am
My RE system: Off Grid System (proposed)- 48 Canadian Solar CS3K-320 panels (15.4 kW) PV array, FXR3048A-01 power center (4 VFXR3648A inverters, 4 FLEXmax-80 charge controllers, 2 - Fortress e-Vault 18.5 kW LFP batteries OR 5 Discover AES 7.4 kW LFP batteries (still undecided), Kohler 14kW backup generator.
Location: Posey, CA

Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by thundley »

Hopefully I am posting this question to the correct forum. The system stated in my profile is the system I am considering but with 48-320 watt panels, the FXR304A-300 looks to be slightly undersized to accommodate 15.4 kW of PV. My question is; can an additional FLEXmax-100 (for a total of 3) be successfully/safely be added to this power center to accommodate the 15.4 kW and also provide some room for growth (if needed)?

Thanks in advance!
raysun
Forum Emperor
Posts: 3326
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: Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by raysun »

Though I use FM80s rather than FM100s, the principals for adding additional PV/charge controller capacity is the same. Any number of charge controllers can be added in parallel, up to the limit of the battery bank charge current acceptance. (Total current can be limited via the Mate's advanced charging menu.)

A battery is not listed in the profile, and is an essential component in calculating the maximum PV array/charge controller capacity. Please update your profile with this critical information.

The other consideration for adding a 3rd FM100 would be the BOS (balance of system) components that need to be added as well. PV disconnect, charge controller disconnect, AFDI protection (which I believe is internal to the FM100, but I'm not authoritative on that), combiner, cabling, etc.
thundley
Forum Member
Posts: 6
Joined: Mon Oct 19, 2020 11:01 am
My RE system: Off Grid System (proposed)- 48 Canadian Solar CS3K-320 panels (15.4 kW) PV array, FXR3048A-01 power center (4 VFXR3648A inverters, 4 FLEXmax-80 charge controllers, 2 - Fortress e-Vault 18.5 kW LFP batteries OR 5 Discover AES 7.4 kW LFP batteries (still undecided), Kohler 14kW backup generator.
Location: Posey, CA

Re: Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by thundley »

Thank you for your reply raysun. I updated my profile to include my proposed batteries which I have not decided on yet. I am working with Wholesale Solar on the design and purchase of this system which with 48 - 320 kW panels is a bit oversized for the two FM-100 charge controllers at 7 kW per charge controller being max on a 48V system. Wholesale Solar is claiming that a third CC can successfully be added but for my peace of mind, I'm looking for some confirmation on this.

In regards to your comments on batteries, I'm being told by WS that the CC's can be programmed to comply with the charging requirements of whatever batteries I choose. Does this sound correct to you?
raysun
Forum Emperor
Posts: 3326
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: Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by raysun »

thundley wrote: Mon Oct 19, 2020 4:16 pm Thank you for your reply raysun. I updated my profile to include my proposed batteries which I have not decided on yet. I am working with Wholesale Solar on the design and purchase of this system which with 48 - 320 kW panels is a bit oversized for the two FM-100 charge controllers at 7 kW per charge controller being max on a 48V system. Wholesale Solar is claiming that a third CC can successfully be added but for my peace of mind, I'm looking for some confirmation on this.

In regards to your comments on batteries, I'm being told by WS that the CC's can be programmed to comply with the charging requirements of whatever batteries I choose. Does this sound correct to you?
Yes, it should be no problem to add a 3rd charge controller. The principal is quite simple and the Outback architecture supports it readily. As with many things, the devil is in the details - that being the proper wiring and BoS parts to maintain the safety of the system. WS should be able to sell you all parts needed, and supply a line drawing for the additional circuitry.

With a solar + battery storage system, what you really have is battery storage + solar charging. The battery is at the heart of the system and all delivered power is routed through the battery bus. How much power can be safely put on the bus is related to how much charging current the battery can handle in its "worst case" state - the beginning of the Bulk charge phase.

The aggregate solar array would be theoretically capable of delivering roughly 320 Amps to the battery. The battery must be capable of accepting 320A charge current, which would take a fairly substantial battery.

The alternative is to put up the 15kW array with no intention of harvesting peak power. The FM100s can easily be "throttled back" to deliver a maximum tailored to the battery's power handling requirements. All that panel acreage would then be intended, not to harvest maximum power on bright, sunny days, but to harvest sufficient power on the more marginal days. This is a good strategy for many locations, as clouds do get in the way.

I'm sure you've walked through the power consumption estimation exercises, and have a ballpark estimate on demand. That, of course, factors into battery capacity sizing as well.
thundley
Forum Member
Posts: 6
Joined: Mon Oct 19, 2020 11:01 am
My RE system: Off Grid System (proposed)- 48 Canadian Solar CS3K-320 panels (15.4 kW) PV array, FXR3048A-01 power center (4 VFXR3648A inverters, 4 FLEXmax-80 charge controllers, 2 - Fortress e-Vault 18.5 kW LFP batteries OR 5 Discover AES 7.4 kW LFP batteries (still undecided), Kohler 14kW backup generator.
Location: Posey, CA

Re: Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by thundley »

So WS contacted Outback today and learned that the FXR3048A-300 power center is currently unavailable and now are trying to sell me the FXR3048-01 power center which has the same 4 inverters but utilizes 4 or the FM-80 CC's instead of the 2 FM-100's. According to WS they will be tying 1-string of 12 PV's into each of the 4 CC's. After looking at the FM-80 specs, I would be under the 4 kW maximum wattage but if I'm reading the specs correctly, I would be way over the "absolute max" voltage of 150V. Each of my panels output 40.1 Voc (x12 = 481V). What am I missing here? Can these charge controllers be programmed to bring the inputs down with-in design specs?

So far I've only been dealing with a sales guy at WS and obviously I will confirm all of this with one of their engineers before I fork out any money. Waiting on the electrical diagrams to arrive before I talk to an engineer.

I appreciate your help with all of this raysun. I am a newbie to solar and have learned gobs over the last several weeks but being the type that can't buy a system without knowing the details of how it works is slowing me down a bit. I've heard that 10% of solar systems fail in one way or the other and out of those 10% that fail, incorrect design accounts for the majority.
raysun
Forum Emperor
Posts: 3326
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: Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by raysun »

The FM80 is a tried-and-true workhorse charge controller. I just installed a FlexPower Two dual FXR3048A and used FM80s. No problem there.

12 320W panels can easily be accomodated by an FM80, but not as a single string of 12. Rather, insist on 6 strings of 2 panels each. All parallel strings terminated in a combiner box, then the output fed to the FM80. Each string will be 80V nominal, well within the FM80 150V input max. On paper, the array could be 4 parallel strings of 3 panels each, but the 120V nominal is pushing things in some environments.
thundley
Forum Member
Posts: 6
Joined: Mon Oct 19, 2020 11:01 am
My RE system: Off Grid System (proposed)- 48 Canadian Solar CS3K-320 panels (15.4 kW) PV array, FXR3048A-01 power center (4 VFXR3648A inverters, 4 FLEXmax-80 charge controllers, 2 - Fortress e-Vault 18.5 kW LFP batteries OR 5 Discover AES 7.4 kW LFP batteries (still undecided), Kohler 14kW backup generator.
Location: Posey, CA

Re: Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by thundley »

The FM80 is a tried-and-true workhorse charge controller. I just installed a FlexPower Two dual FXR3048A and used FM80s. No problem there.
Great to hear this on the FM-80. I tend to try and go with the latest and greatest which I suspect the FM-100 is from OP but not necessarily "tried and true".
12 320W panels can easily be accomodated by an FM80, but not as a single string of 12. Rather, insist on 6 strings of 2 panels each. All parallel strings terminated in a combiner box, then the output fed to the FM80. Each string will be 80V nominal, well within the FM80 150V input max. On paper, the array could be 4 parallel strings of 3 panels each, but the 120V nominal is pushing things in some environments.
Just the info I needed, thanks raysun! At least now I know that I'm reading the spec sheets correctly. It will be interesting to see if WS comes up with this same string sizing in their electrical drawings, will let you know. Much appreciated!
raysun
Forum Emperor
Posts: 3326
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: Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by raysun »

Is this planned as an off-grid or grid-tied system?
thundley
Forum Member
Posts: 6
Joined: Mon Oct 19, 2020 11:01 am
My RE system: Off Grid System (proposed)- 48 Canadian Solar CS3K-320 panels (15.4 kW) PV array, FXR3048A-01 power center (4 VFXR3648A inverters, 4 FLEXmax-80 charge controllers, 2 - Fortress e-Vault 18.5 kW LFP batteries OR 5 Discover AES 7.4 kW LFP batteries (still undecided), Kohler 14kW backup generator.
Location: Posey, CA

Re: Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by thundley »

Totally off-grid
thundley
Forum Member
Posts: 6
Joined: Mon Oct 19, 2020 11:01 am
My RE system: Off Grid System (proposed)- 48 Canadian Solar CS3K-320 panels (15.4 kW) PV array, FXR3048A-01 power center (4 VFXR3648A inverters, 4 FLEXmax-80 charge controllers, 2 - Fortress e-Vault 18.5 kW LFP batteries OR 5 Discover AES 7.4 kW LFP batteries (still undecided), Kohler 14kW backup generator.
Location: Posey, CA

Re: Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by thundley »

To confirm, is this what you were recommending in regards to string sizing raysun?
String Sizing.JPG
raysun
Forum Emperor
Posts: 3326
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: Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by raysun »

thundley wrote: Mon Oct 19, 2020 7:55 pm To confirm, is this what you were recommending in regards to string sizing raysun?

String Sizing.JPG
Yep. 2S x 6P array. FM80s will handle that all day, in any weather condition.

For totally off-grid, FM80s are just fine.
fcwlp
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Posts: 648
Joined: Wed Jan 22, 2020 9:40 am
My RE system: GS8048A, FM80 w/3,600W 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 install and maintain grid-tied and off-grid systems in my area and consult on solar system design/operation.
Location: 80 miles NE of Phoenix at 5500'

Re: Adding a third FLEXmax-100 to the FXR3048A-300 FLEXpower FOUR Power Center

Post by fcwlp »

@thundley, since you are not near the coast, you may want to consider a VFXR3648 based system. This is the vented version which for four inverters gets you an additional 2,400VA.

Both the FM80 and FM100 are very good CCs. The FM100 has built-in GFI and AFCI. The FM80 uses a GFI breaker in the load center. If I was putting on the roof of my home, I would go with the FM100. As you are in CA, I would check with local AHJ (Authority Having Jurisdiction) on what NEC you have to follow. The FM100 is easier to implement with the 2017 NEC and later.
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