diy solar

diy solar

8 solar panels in series to two inverters.

Guido81

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Jan 24, 2022
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Hi,

Beginner here ;-)

Last year i ordered 2 Growatt 5kW Stackable Off-Grid Inverters | SPF 5000 ES-US plus 2 EG4-LifePower4 Lithium Batteries | 48V 100AH.

I am just now setting it up and something is not clear to me.

I have 8, 450 watt 48v solar panels. I can put them all in series and have 384v going trough one black and red cable going to my house. I can connect that to one inverter since the inverter can handle 450v.

But how do i connect it to two inverters? And do i need to connect it to two inverters? I think i need to because they need solar and battery input right?

The inverters will be in parallel.

So can i split the red and black cable in the house and then connect to both inverters? Or do i need to put four solar panels in series and connect to one inverter and then put the other 4 solar panels in series and connect to the other inverter?

I attached an image on how i think i should do it. This way it's only going to be one red and one black cable coming form my solar panels. About 120feet away.

Thanks
Guido
 

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What is the minimum voltage your inverter needs from solar to function? That would be the only constraint that might require a different solution
 
The inverters dont both need PV input. They do have to be connected the the same battery.
you also list 3600w of PV for 10Kw of inverter. The performance of such a system will be..... extremely limited.
 
It's all in you manual. Just look for a pic that looks like this. The batteries must be wired in parallel, becuase the two units must be receiving exactly the same DC voltage.
1655737380349.png
 
....you also list 3600w of PV for 10Kw of inverter. The performance of such a system will be..... extremely limited.
Yes, the amount of loads that can be supported when the grid goes down will be limited. If he has a grid connection he can charge from the grid. In any scenerio the limitation will be the 4.8 kWh of batteries. There is enough solar to produce at least 10 kWh of energy depending on location.
 
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I have 8, 450 watt 48v solar panels. I can put them all in series and have 384v going trough one black and red cable going to my house. I can connect that to one inverter since the inverter can handle 450v.

450V / 384V = 1.17, 17% headroom which I know is sufficient that cold weather won't boost voltage too much.

Assuming 384V is Voc, not Vmp.

384V / 8 panels = 48V per panel, a very round number.

What are the PV panel specs?
 
450V / 384V = 1.17, 17% headroom which I know is sufficient that cold weather won't boost voltage too much.

Assuming 384V is Voc, not Vmp.
most of the 450w panels I can google suggest Voc between 41 and 49v so the "nice round" 48v is reasonable.

however my smell detector is leaning toward the "this is all on paper still and nothing has actually been purchased yet"
 
What is the minimum voltage your inverter needs from solar to function? That would be the only constraint that might require a different solution
Hi thanks for your reply. I think it needs at least 120v.
 
The inverters dont both need PV input. They do have to be connected the the same battery.
you also list 3600w of PV for 10Kw of inverter. The performance of such a system will be..... extremely limited.
I have 10kw inverters and 10kw batteries. So the solar would be sufficient to charge the batteries on average. And we cut down on usage in the house. The plan will be to buy more solar panels eventually. We are going off grid partially and fully off grid later down the road.
 
Yes, the amount of loads that can be supported when the grid goes down will be limited. If he has a grid connection he can charge from the grid. In any scenerio the limitation will be the 4.8 kWh of batteries. There is enough solar to produce at least 10 kWh of energy depending on location.
Hi Ampster, i have 10kw of batteries. ;-)
 
450V / 384V = 1.17, 17% headroom which I know is sufficient that cold weather won't boost voltage too much.

Assuming 384V is Voc, not Vmp.

384V / 8 panels = 48V per panel, a very round number.

What are the PV panel specs?
I have attached a pdf with specs. I have the 450.
 

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most of the 450w panels I can google suggest Voc between 41 and 49v so the "nice round" 48v is reasonable.

however my smell detector is leaning toward the "this is all on paper still and nothing has actually been purchased yet"
Hi schmism, everyhting is purchased already ;-) Setting it al up as we speak.
 
Thank you all for your replies! So i also got confirmation from the company i bought it from and the said that if the inverters are in parallel then connecting to one inverter is enough. :)
 
I have attached a pdf with specs. I have the 450.

Gives a full set of specs at both STC and NOCT
49.6Voc (STC), 11.58A Isc (STC)
8 x 49.6Voc = 396.8Voc string. 396.8Voc x 1.16 = 460.3V conservative estimate in cold weather. (time to sharpen the pencil)
(I use +16% Voc assuming 40 degrees below nominal and temperature coefficient -0.4%/degree C.)

Temperature Coefficient of Voc -0.265%/degree C.
Consider operation at -15 degrees C vs. +25 degrees:
(-15 - +25) x -0.00265 = +0.106; +10.6% voltage when operated 40 degrees below nominal

49.6 x 1.106 = 54.9Voc in cold weather
8 x 54.9 = 438.9Voc string in cold weather.

Eight panels in series OK at -15 degrees C (and even a bit colder) for 450V max input spec.

Pmax 450W (STC), 337.3W (NOCT)
337.3W/450W = 0.75; expect 75% of rated power under nominal conditions. A bit lower than some other panels which might deliver 85%
 
Thank you all for your replies! So i also got confirmation from the company i bought it from and the said that if the inverters are in parallel then connecting to one inverter is enough. :)
I would run 4s1p to each inverter and use 10awg wires to run from panels to inverters. since you plan to put in more panels you could do up to 6s2p per inverter (24 panels) with no additional wiring. Makes it easy to add panels later and not have to run new wires to the inverters every time. top production might get clipped if higher than 18 or 22 amp depending on your inverters but would help production on cloudy days.
 
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