What's the Differences between FXR, Radian and Skybox

True Hybrid Energy System
Post Reply
sparksalot
Forum Guru
Posts: 314
Joined: Sun Jul 17, 2016 5:31 am
My RE system: FLEXpower TWO VFXR3648A Grid-Tied and Battery Backup Hybrid, Mate3s
Using Two Midnite 200 Classic Charge Controllers

Traction battery FLA 48 volt 805Ahr.

32 SolarWorld 245w mono, 2x-4S-4P
6 REC 320w on micro-inverters

What's the Differences between FXR, Radian and Skybox

Post by sparksalot » Mon Oct 07, 2019 2:45 pm

Could someone put the feature differences of all three in one response or reply?

Mike Curran
Forum Emperor
Posts: 1817
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB inverter/charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: What's the Differences between FXR, Radian and Skybox

Post by Mike Curran » Mon Oct 07, 2019 5:10 pm

Sparks - I'm no expert, but I'll take a stab at it.

The Skybox incorporates a built-in charge controller that will accept up to 5000 watts input at 600V DC max. It will (soon) accept an AC array coupled to its output, just as the Radian can. The FXR will not. It will work with or without a battery, whereas I don't think the others can. It has a lower power throughput rating than the larger Radians but can be stacked, as the others can. Skybox is split phase 120/240V AC whereas the FXR must be paired to get this. The Radians also have 120/240V capability. Skybox has built-in monitoring (no Mate3s or FNDC required).

There's probably more to set the Skybox apart but like I said, not an expert. - Mike
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

sparksalot
Forum Guru
Posts: 314
Joined: Sun Jul 17, 2016 5:31 am
My RE system: FLEXpower TWO VFXR3648A Grid-Tied and Battery Backup Hybrid, Mate3s
Using Two Midnite 200 Classic Charge Controllers

Traction battery FLA 48 volt 805Ahr.

32 SolarWorld 245w mono, 2x-4S-4P
6 REC 320w on micro-inverters

Re: What's the Differences between FXR, Radian and Skybox

Post by sparksalot » Mon Oct 07, 2019 7:18 pm

Thanks Mike, That is a good explanation. That helps me and I'm sure it helps others too.

As for a FXR not taking AC arrays at output, is that a physical limitation on lug terminals, or a electronic internal limitation?
I have 4 PV panels with micro inverters besides the 30 panels on string inverters and thought the micros were working fine. Never checked them after disconnecting Main Breaker from grid though. They're connected at the Critical Loads panel so their production displaces other string inverter power there which then in turn sends that offset to the Main Dist. Panel. and what's left over there is sent to the grid. Is what I described something different from the others?

Mike Curran
Forum Emperor
Posts: 1817
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB inverter/charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: What's the Differences between FXR, Radian and Skybox

Post by Mike Curran » Tue Oct 08, 2019 7:21 am

As for a FXR not taking AC arrays at output, is that a physical limitation on lug terminals, or a electronic internal limitation?
Actually, there's no physical or electronic reason for this, except that the FXR does not have an internal method to prevent overcharging your battery when an AC source feeds back through the inverter to the DC output at a constant 25 amps. So if you wanted to do this you'd need a good way to control the charging so that you don't damage your battery. The Radian and Skybox both use frequency dithering (slightly raising the frequency of their AC output) to force the AC coupled source to shut off when the battery is charged. The other method OB has used (before they adopted frequency shifting) has been to sense battery voltage getting high and use an aux contact to operate a relay that would open the connection of the AC source to the fxr's output. This method isn't as reliable as frequency shift as it introduces a mechanical device and the voltage detection has to be spot on, especially for Lithium batteries.

Edit: If your critical loads panel is fed from your FXR output, then your microinverters have the potential to overcharge your battery (back through the fxr) if you don't have some sort of control mechanism in place.
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

sparksalot
Forum Guru
Posts: 314
Joined: Sun Jul 17, 2016 5:31 am
My RE system: FLEXpower TWO VFXR3648A Grid-Tied and Battery Backup Hybrid, Mate3s
Using Two Midnite 200 Classic Charge Controllers

Traction battery FLA 48 volt 805Ahr.

32 SolarWorld 245w mono, 2x-4S-4P
6 REC 320w on micro-inverters

Re: What's the Differences between FXR, Radian and Skybox

Post by sparksalot » Tue Oct 08, 2019 3:51 pm

Alright, Thanks, but I might need some more explaining.

I am Grid Tied and my Sell Voltage doesn't let my battery voltage go above that setting in the Mate3s.
And besides being grid tied my batteries are only maintained in PV Float since they are only used as a Backup to the Critical Loads.
I always thought the Critical Loads output had no way to backfeed the inverter. My 4 micros only displace or offset a small portion of the Critical Loads there anyways.
The Sell Voltage sent to the Grid comes from the separate inverter output bi-directional feed to the MDP. And that bi-directional output is also the source to use the Grid for AC Charging and also is the Bypass AC source bypassed through the FXR's other AC output and on into Critical Loads panel during FXR system outages.

Why should I be concerned?
Where would your referenced constant 25 ADC come from?

Note: I do not use any OB charge controllers, so my Mate3s knows not what happens for that aspect either, if it matters.
Last edited by sparksalot on Tue Oct 08, 2019 4:36 pm, edited 1 time in total.

Mike Curran
Forum Emperor
Posts: 1817
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB inverter/charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: What's the Differences between FXR, Radian and Skybox

Post by Mike Curran » Tue Oct 08, 2019 4:34 pm

Why should I be concerned?
Good point about your sell setting preventing battery voltage to rise. But what would happen when the grid goes down? Your AC modules would charge the battery, unregulated.

Not sure where I got the 25A figure, must've read it somewhere but can't put my finger on it right now. Just know that during a grid outage if you're generating more than you're using, the AC modules will backfeed DC current to your battery without any controls on it, so I guess charging current flow depends on your AC modules' output and what you're using in your house. Again, that's if you have a grid outage. I overlooked this in my earlier posts. - Mike
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

sparksalot
Forum Guru
Posts: 314
Joined: Sun Jul 17, 2016 5:31 am
My RE system: FLEXpower TWO VFXR3648A Grid-Tied and Battery Backup Hybrid, Mate3s
Using Two Midnite 200 Classic Charge Controllers

Traction battery FLA 48 volt 805Ahr.

32 SolarWorld 245w mono, 2x-4S-4P
6 REC 320w on micro-inverters

Re: What's the Differences between FXR, Radian and Skybox

Post by sparksalot » Tue Oct 08, 2019 4:42 pm

Oh, okay. thanks again, Mike.

I use the Enphase M215 micros, so then if they like the FXR's AC output (V and Hz) well enough and don't get dropped, I would still have their output offsetting the FXR Critical Loads during a grid loss.
I may have to test this out to see what would happen.

Now you have me wondering how my AC generator, during grid loss, is regulated through the FXR to charge the batteries???

Mike Curran
Forum Emperor
Posts: 1817
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB inverter/charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: What's the Differences between FXR, Radian and Skybox

Post by Mike Curran » Tue Oct 08, 2019 5:03 pm

Where is your AC generator connected? If it's connected to the Gen input on your fxr then the fxr will regulate charging to the battery. But if it's connected to the fxr AC output (which I doubt) then it too would charge your batteries, unregulated, during a grid outage.
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

sparksalot
Forum Guru
Posts: 314
Joined: Sun Jul 17, 2016 5:31 am
My RE system: FLEXpower TWO VFXR3648A Grid-Tied and Battery Backup Hybrid, Mate3s
Using Two Midnite 200 Classic Charge Controllers

Traction battery FLA 48 volt 805Ahr.

32 SolarWorld 245w mono, 2x-4S-4P
6 REC 320w on micro-inverters

Re: What's the Differences between FXR, Radian and Skybox

Post by sparksalot » Tue Oct 08, 2019 6:48 pm

Mike Curran wrote:
Tue Oct 08, 2019 5:03 pm
Where is your AC generator connected? If it's connected to the Gen input on your fxr then the fxr will regulate charging to the battery. But if it's connected to the fxr AC output (which I doubt) then it too would charge your batteries, unregulated, during a grid outage.
Ahh, FXR only has AC IN and AC OUT.

I have a separate ATS (DPDT) that flips from either Grid or to the Generator both common to the Main Breaker of the MDP where FXR AC IN breaker also resides...which is bi-directional.

As for Critical Loads Panel...that would be the AC OUT from FXR...never needs to go but one direction, if that's even possible. Never has gone but one direction that I'm aware of.

Mike Curran
Forum Emperor
Posts: 1817
Joined: Sat Aug 28, 2004 6:28 pm
My RE system: Outback - Garage roof:
- 8 (2x4) Evergreen 180's into one FM80 (2007/2020 - replaced MX60)
- 6 (2×3) ALEO S79-300's into one FM80 (2017)
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC (2007)
- 12 Surrette/Rolls 2V x 1766Ah (2007)
- Hub10.3, Mate3s, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar - Barn roof: (2012)
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied

Outback Skybox - Barn roof: (2019)
- 14 Talesun 275W in series (DC array input to SB inverter/charger)
- 3 SimpliPhi 3.8 batteries, 48V, 225Ah total
- AC coupled input (manual switch during grid outage only) from 14 Talesun 275W,
Enphase M215 microinverters, normally direct grid tied

All self-designed and self-installed
Location: Chagrin Falls, Ohio

Re: What's the Differences between FXR, Radian and Skybox

Post by Mike Curran » Tue Oct 08, 2019 7:23 pm

If your M215 panels are connected to the critical loads panel, then during a grid outage they could potentially feed "backwards" through your fxr, invert to DC, and charge your battery without any control. Again, depends on your house loads and PV input from the M215 panels.

Sounds like your generator is on the "AC in" side of your vfxr's so no worries there.
http://www.tigoenergy.com/site.php?95b2dca2-ca6c
https://enlighten.enphaseenergy.com/public/systems/Hctc107221

sparksalot
Forum Guru
Posts: 314
Joined: Sun Jul 17, 2016 5:31 am
My RE system: FLEXpower TWO VFXR3648A Grid-Tied and Battery Backup Hybrid, Mate3s
Using Two Midnite 200 Classic Charge Controllers

Traction battery FLA 48 volt 805Ahr.

32 SolarWorld 245w mono, 2x-4S-4P
6 REC 320w on micro-inverters

Re: What's the Differences between FXR, Radian and Skybox

Post by sparksalot » Tue Oct 08, 2019 8:36 pm

While connected to Grid the Battery's Sell Voltage setting in Mate3s will sell anything before batteries could ever get over charged.
And during any day time grid loss the batteries have been likely already discharged from night before and are discharging still anyways because they are the sole source for all critical loads..so no worries. :smile:
Last edited by sparksalot on Tue Oct 08, 2019 8:46 pm, edited 1 time in total.

Post Reply