Panel hook up advice for a newbie

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Panel hook up advice for a newbie

Postby Cottonk on Fri Jan 12, 2018 4:23 pm

Alright folks here is my question. I'm getting ready to hook up my vfxr3648a-01, I have 8 solar panels that are showing an open circuit voltage of 39.8 and a rated voltage of 32.3 with short circuit current of 9.78 amp and rated current of 9.25 amp these are 295 watt mono panels and are off grid. How should these be wired?
Cottonk
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Posts: 3
Joined: Fri Jan 12, 2018 2:55 pm
My RE system: Outback FP1 VFXR 3648A-01
8- 295W solarworld mono
8- Trojan L16RE-B 370 amp hr
Off grid

Re: Panel hook up advice for a newbie

Postby pss on Fri Jan 12, 2018 5:33 pm

That model inverter accepts a 48 volt battery bank. Your panels are 8 at 295 watts = 2360 watts. If you connect in a 2 x 4 array (2 in series, then 4 in parallel), your will Voc will be about 80 and your system will use a combiner box with 4 circuit breakers at 15 amps each. Your input would be a Flexmax 60 charge controller connected to your battery bank and your batteries to your inverter. Your battery bank should be 1 or 2 strings of 6 volt lead acids, wired 8 in a series for 48 volts. This would do well for you.
pss
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My RE system: 7800 watts in three strings, Flexmax 60 x 3, Radian 8046A, GLSC load center, Mate 3, Hub 10.3 and 900 Amp, 48V Trojan T105-RE battery bank.

Re: Panel hook up advice for a newbie

Postby Cottonk on Fri Jan 12, 2018 5:39 pm

Another question. Since I'm running the pre wired flex power one that is set up for 48v will my input not have to be 48v from the panels?
Cottonk
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Posts: 3
Joined: Fri Jan 12, 2018 2:55 pm
My RE system: Outback FP1 VFXR 3648A-01
8- 295W solarworld mono
8- Trojan L16RE-B 370 amp hr
Off grid

Re: Panel hook up advice for a newbie

Postby Mike Curran on Fri Jan 12, 2018 5:41 pm

For your 48 volt system, your 8 × 295 watt = 2360 watts is well within your charge controller's 4000 watt recommended design maximum, assuming it's an FM80. Or even an FM60's 3200 watt max. However, OB's charge controllers (aside from FM100's) don't like any panel wiring arrangement where open circuit voltage exceeds 150 volts. A manual screenshot is attached, fyi.

So the optimum arrangement would be wiring your panels 3 in series, then each 3 panel string would be wired in parallel with the others. However with only 8 panels, you'd end up with a third, 2 panel string which wouldn't be compatible with the other 3 panel strings.

So you have two choices: add one more 295W panel, then you'd have 3, 3 panel series strings wired in parallel; or, wire your panels 2 in series, so you'd have 4, 2 panel strings wired in parallel. This latter arrangement could be marginal in operation since in a 48V system the FM80 wants to see an input voltage higher than 48V and in low light conditions 2 in series might not meet this threshold.

Sorry for the long-winded response. Maybe someone else will have a better idea (and say it with brevity :grin: ).
Screenshot_20180112-192446.png
Mike Curran
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Posts: 429
Joined: Sat Aug 28, 2004 6:28 pm
Location: Chagrin Falls, Ohio
My RE system: Outback:
- 8 (2x4) Evergreen 180's into one MX60
- 6 (2×3) ALEO S79-300's into one FM80
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC
- 12 Surrette/Rolls 2V x 1766Ah
- Hub10.3, Mate3, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

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

Re: Panel hook up advice for a newbie

Postby pss on Fri Jan 12, 2018 5:54 pm

I think you do not have to worry about clouds with a 2 x 4 arrangement. I know, cause I use one. Your voltage will be at least 58 volts on cloudy days and your MPPT controller will usually charge at about 54-56 volts, so no worries. That is the real facts. Your amperage is low on cloudy days, but voltage is okay.
As for a 3 x 3 array, the, the Voc will be higher, but laying out the panels this way requires three columns of panels laid horizontally if on the ground. Otherwise the panels, if arranged vertically with say a length of 70 inches each would be 212 inches or 17.66 feet requiring a very long rail! If roof mounting, this may not be a problem and if that's the case, I would do a 3 x 3. But ground mount works best with 2 x 4 or 2 x 5 and panels arranged vertically.
pss
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Posts: 53
Joined: Mon Jul 24, 2017 8:40 am
My RE system: 7800 watts in three strings, Flexmax 60 x 3, Radian 8046A, GLSC load center, Mate 3, Hub 10.3 and 900 Amp, 48V Trojan T105-RE battery bank.

Re: Panel hook up advice for a newbie

Postby pss on Fri Jan 12, 2018 5:59 pm

Your panels do not have to have a 48 volt input. What you have to have is a panel voltage about 15-20 volts above your battery bank voltage as ideal. This allows for equalization of the batteries. But, you can always equalize with the charger on the inverter using a generator or the grid. You said your panels are 32.3 volts. Times 2 = 64.6, well above 48 volts. So, if your panels input 58-62 volts into your charge controller, the charge controller itself, through the MPPT program will usually reduce this voltage to about 55-56 to push more amps into the batteries. Thats the facts.
pss
OutBack Expert
 
Posts: 53
Joined: Mon Jul 24, 2017 8:40 am
My RE system: 7800 watts in three strings, Flexmax 60 x 3, Radian 8046A, GLSC load center, Mate 3, Hub 10.3 and 900 Amp, 48V Trojan T105-RE battery bank.

Re: Panel hook up advice for a newbie

Postby Mike Curran on Sat Jan 13, 2018 11:36 am

pss wrote:I think you do not have to worry about clouds with a 2 x 4 arrangement. I know, cause I use one. Your voltage will be at least 58 volts on cloudy days and your MPPT controller will usually charge at about 54-56 volts, so no worries. That is the real facts. Your amperage is low on cloudy days, but voltage is okay.
As for a 3 x 3 array, the, the Voc will be higher, but laying out the panels this way requires three columns of panels laid horizontally if on the ground. Otherwise the panels, if arranged vertically with say a length of 70 inches each would be 212 inches or 17.66 feet requiring a very long rail! If roof mounting, this may not be a problem and if that's the case, I would do a 3 x 3. But ground mount works best with 2 x 4 or 2 x 5 and panels arranged vertically.


Well said, pss! Experience counts - but I just took a look at my 2×4 (4 panels in series, × 2) Evergreen 180 array voltage and it reads 93V. That's 93÷4=23.3V/panel for panels with V(p) = 25.9V and V(oc) = 32.6V. Maybe Cottonk's panel voltage ratings are high enough to allow charging his 48V bank, mine are puny compared to his. And again, your experience with 2 panels in series counts!
Mike Curran
OutBack Guru
 
Posts: 429
Joined: Sat Aug 28, 2004 6:28 pm
Location: Chagrin Falls, Ohio
My RE system: Outback:
- 8 (2x4) Evergreen 180's into one MX60
- 6 (2×3) ALEO S79-300's into one FM80
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC
- 12 Surrette/Rolls 2V x 1766Ah
- Hub10.3, Mate3, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

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

Re: Panel hook up advice for a newbie

Postby pss on Sat Jan 13, 2018 7:14 pm

Mike, from what you wrote, if your panels were 2 x 2, your input voltage to charge your batteries would be 51.8 volts, not enough to charge a 48 volt battery bank reliably. That is because the power of your panels is too low. Only 180 rated watts. If you put three in series, it would become 77.7 volts and would be enough to charge a 48 volt battery bank. The Voc is the manufacturer's reported voltage between the positive and negative terminals when the panel is in the full sun and no current is flowing. If you hook up a charge controller and batteries to the panel, you should be able to reach the Vmp under ideal sunlight and temperatures. This will be reported as volts and amps by the charge controller whose MPPT program will then reduce the voltage and increase the amperage to allow more power to flow into the batteries. Battery charging is optimized at a lower voltage and higher amperage. The Voc is what is limited to 150 volts by the performance design of the charge controller. Under that maximum, then becomes the amperage allowed to flow through the controller. This is limited by the circuit design and gauge of the wires into and out of the controller. The Vmp is always lower than the Voc as long as there is a flow of current. So, like I said, a 64.6 volt output will charge a 48 volt battery bank quite well. Most 48 volt banks are considered charged at anywhere from 56.7 to 58.4 volts. Could the "newbie" do a 3 panels series, of course, but he has 8 panels, not 9 or 12. So he has only one way to connect them, 2 x 4.

Now, Mike, know you have a tremendous amount of expertise (and have helped me too), and you know what I am writing. I have simplified it not to explain to you, but for those looking for information and current and future newbies to understand.
pss
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Posts: 53
Joined: Mon Jul 24, 2017 8:40 am
My RE system: 7800 watts in three strings, Flexmax 60 x 3, Radian 8046A, GLSC load center, Mate 3, Hub 10.3 and 900 Amp, 48V Trojan T105-RE battery bank.

Re: Panel hook up advice for a newbie

Postby blackswan555 on Sat Jan 13, 2018 11:10 pm

2 strings of 4 is over max VOC, 4 strings of 2 is just about there with VMP voltage, Any chance of adding one more panel ? 3x3 would be a better option if it was possible,

Tim
My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.
blackswan555
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Re: Panel hook up advice for a newbie

Postby Cottonk on Sun Jan 14, 2018 12:08 pm

Thanks for the advice. Any recommendations for a combiner
Cottonk
Junior Member
 
Posts: 3
Joined: Fri Jan 12, 2018 2:55 pm
My RE system: Outback FP1 VFXR 3648A-01
8- 295W solarworld mono
8- Trojan L16RE-B 370 amp hr
Off grid

Re: Panel hook up advice for a newbie

Postby pss on Sun Jan 14, 2018 12:57 pm

Midnite Solar combiner. Also, their breakers for the box. Get a DC disconnect switch, one that is fuse capable and a lightening arrestor for the combiner box.. Ground all of your panels at the array with a grounding rod into the ground.
9 panels is better than 8.
pss
OutBack Expert
 
Posts: 53
Joined: Mon Jul 24, 2017 8:40 am
My RE system: 7800 watts in three strings, Flexmax 60 x 3, Radian 8046A, GLSC load center, Mate 3, Hub 10.3 and 900 Amp, 48V Trojan T105-RE battery bank.

Re: Panel hook up advice for a newbie

Postby blackswan555 on Sun Jan 14, 2018 7:56 pm

My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.
blackswan555
OutBack Emperor
 
Posts: 2562
Joined: Sat Aug 30, 2008 5:50 am
Location: Ibiza Spain,
My RE system: Other peoples, VFX "E" versions, FLA`s, Generators.

Re: Panel hook up advice for a newbie

Postby pss on Sun Jan 14, 2018 8:02 pm

OUTBACK FWPV6 FLEXWARE INTEGRATED COMBINER BOX

Will do the job and at a good price. Add DC breakers and a DC lightening arrestor.
pss
OutBack Expert
 
Posts: 53
Joined: Mon Jul 24, 2017 8:40 am
My RE system: 7800 watts in three strings, Flexmax 60 x 3, Radian 8046A, GLSC load center, Mate 3, Hub 10.3 and 900 Amp, 48V Trojan T105-RE battery bank.


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