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Growatt inverter and parallel solar panel wiring

Hidden valley

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Sep 3, 2021
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I have a 5000 growatt grid tied inverter kit from signature solar and I was wondering how many 360W 60Cell Black Mono Solar Panel by Solarever that I can connect in parallel before I go over the amperage allowed by the inverter or mppt?
 
Here are my panels and my inverter. It doesn't look like I can run panels in parallel unless I connect them to separate inputs on my mppt.


1632508503148.jpeg1632508417480.jpeg
 
You really need to spend some time in the beginners corner if have these products on hand and don't understand something as basic as parallel panels increase current and series panels increase voltage.

Presuming you know that's a grid tie only inverter....

That unit has two PV inputs. each input will support 12.5a at 550v.
So a single series string of between 13 and 16 panels is what one input will handle.
 
Last edited:
Here are my panels and my inverter. It doesn't look like I can run panels in parallel unless I connect them to separate inputs on my mppt.
The inverter is not designed to run panels in parallel, nor is there a need to run panels in parallel.

The inverter has two high voltage (550V) MPPT inputs so you would connect a single string of panels in series to each MPPT.

With a panel Voc of 41.2V, and allowing for some voltage increase in cold conditions, you probably have a safe maximal string limit of 11 panels in series, maybe 12 if you never get all that cold (e.g. 0°C).

20 panels @ 360W = 7200W which is more than ample for this inverter. 18 of those panels is probably a better array size for this inverter.

e.g. that could be 2 strings of 9 or 10 panels in series, each feeding an MPPT input.
 
Does it matter is I have different length of electrical runs between panels that are in a series?
 
Here are the numbers for those panels (was looking at them also). The temps are the cell temp.

C T
F T
VOC
Pmax
Isc
-60​
-76​
51.36​
467.10​
10.70​
-55​
-67​
50.76​
460.80​
10.73​
-50​
-58​
50.16​
454.50​
10.76​
-45​
-49​
49.56​
448.20​
10.79​
-40​
-40​
48.97​
441.90​
10.81​
-35​
-31​
48.37​
435.60​
10.84​
-30​
-22​
47.77​
429.30​
10.87​
-25​
-13​
47.17​
423.00​
10.89​
-20​
-4​
46.58​
416.70​
10.92​
-15​
5​
45.98​
410.40​
10.95​
-10​
14​
45.38​
404.10​
10.97​
-5​
23​
44.78​
397.80​
11.00​
0​
32​
44.19​
391.50​
11.03​
5​
41​
43.59​
385.20​
11.05​
10​
50​
42.99​
378.90​
11.08​
15​
59​
42.39​
372.60​
11.11​
20​
68​
41.80​
366.30​
11.13​
25​
77​
41.20​
360.00​
11.16​
30​
86​
40.60​
353.70​
11.19​
35​
95​
40.01​
347.40​
11.21​
40​
104​
39.41​
341.10​
11.24​
45​
113​
38.81​
334.80​
11.27​
50​
122​
38.21​
328.50​
11.29​
55​
131​
37.62​
322.20​
11.32​
60​
140​
37.02​
315.90​
11.35​
65​
149​
36.42​
309.60​
11.37​
70​
158​
35.82​
303.30​
11.40​
75​
167​
35.23​
297.00​
11.43​
80​
176​
34.63​
290.70​
11.45​
 
The inverter is not designed to run panels in parallel, nor is there a need to run panels in parallel.

The inverter has two high voltage (550V) MPPT inputs so you would connect a single string of panels in series to each MPPT.

With a panel Voc of 41.2V, and allowing for some voltage increase in cold conditions, you probably have a safe maximal string limit of 11 panels in series, maybe 12 if you never get all that cold (e.g. 0°C).

20 panels @ 360W = 7200W which is more than ample for this inverter. 18 of those panels is probably a better array size for this inverter.

e.g. that could be 2 strings of 9 or 10 panels in series, each feeding an MPPT input.
I understand this is an old thread but since Google search put this on top of the search, I thought I will post additional questions that are pertinent here. I am an ECE&S professor but have been working in different areas but looking at an installation as I am retired now.:
1. I notice that there is an additional spec. for the MPPT which generally is not shown in the sales page of most sellers. For example, I am looking at

Growatt 3kW Stackable Off-Grid Inverter | SPF 3000TL LVM-ES​

which is a 48V system (and can work on the solar or the grid) , the manual says, Start-up Voltage is 150V DC, I suppose for the MPPT to work. Is this 150V based on Voc or operarting voltage (I bought four old 24V panels as a start that have 37.5 for Voc and 30.x for Vop)? With 4 panels, I am barely satisfying this condition using te higher Voc and as someone else pointed, we have the voltage variation based on the temperarture (I live in Tucson).
2. "Open circuit Voltage (Voc) of PV modules should be higher than min. battery voltage (which is 48V)." - I hope (s)he is referring to the voltage seen by the MPPT terminals (that might be a series connection of panels) and not the individual panel voltage. If former, this is sort of redundant given the very high start up voltage needed.
3. This model aslo claims this can be used without a battery (hence my interest as I want to grow the system slowly and not accumualte all parts immediately as there is a chance I might vanish from the earth anytime! Also, I am living in a rental house with HOA restrictions with the accompanying restrictions. Luckily my backyard is barren and south facing and I plan for a ground mount with home made angle adjustable mount). Reading the elctronic I understand the reason for the battery (providing a reference voltage for the MPPT / operating point for the solar panel). So, how do they overcome the need for a battery in this model? Are they using grid voltage and use a AC to 48V DC converter internally?
I may have more questions later as I ponder the various issues.
It looks like this webpage does't use spell check and few keys in my KB are sort of stuck.
Thank you.
 
Is this 150V based on Voc or operarting voltage
Operating voltage. Most MPPTs have a minimum string voltage rating required to operate.

"Open circuit Voltage (Voc) of PV modules should be higher than min. battery voltage (which is 48V)." - I hope (s)he is referring to the voltage seen by the MPPT terminals (that might be a series connection of panels) and not the individual panel voltage. If former, this is sort of redundant given the very high start up voltage needed.
yes, redundant but it can happen with some models with a much lower MPPT voltage range.

As for batteryless, I'm not sure exactly how it works but I'm not sure I'd recommend using it in that mode anyway. Better to have some battery than none.
 
Operating voltage. Most MPPTs have a minimum string voltage rating required to operate.


yes, redundant but it can happen with some models with a much lower MPPT voltage range.

As for batteryless, I'm not sure exactly how it works but I'm not sure I'd recommend using it in that mode anyway. Better to have some battery than none.
Thanks for quick response.
Regarding battery Vs No battery, I found these descriptions in the manuals:
A. This for unit which seems to need the battery. See the word, transformerless design: "This is a multifunctional off grid solar inverter, integrated with a MPPT solar charge controller, a highfrequency pure sine wave inverter and a UPS function module in one machine, which is perfect for off gridbackup power and self-consumption applications. The transformerless design provides reliable powerconversion in compact size."
B. For the unit which says, works with or without battery: "This is a multifunctional off grid solar inverter, integrated with a MPPT solar charge controller, a highfrequency pure sine wave inverter and a UPS function module in one machine, which is perfect for off gridbackup power and self-consumption applications. This inverter can work with or without batteries." They even use the term, UPS, which implies AC to DC to charge.
Even though the description for one says compact size, the one with transformer is only 0.5Kg more.
I am not going to operate the system without battery forever. I want to build and test one section at a time without accumulating all the stuff and feel overwhelmed.

I have few more questions for you.
1. I have 4 old panels that in series gives a Voc of 150.4 (4x37.6) which is barely above the 150V the batteryless unit calls as a start-up voltage (I guess needed for the MPPT to kick in in the absence of a battery). Ironically start-up voltage is specified inside the detailed manual and not the 2-3 page spec sheet. Also the MPPT operating range is 120 to 240V which places my 4 panel op. voltage of 121.2V just little above the minimum.
2. On the otherhand, if I go for the other model, the spec. MPPT Range @ Operating Voltage is 35V to 115V (my 4 series panel string would put it at 121.2V) causing me some concern. But talking to myself, I can say the op. point is determined by the MPPT (and not the solar panels) and hence I shoud not be concerned (well, the panels will operate at a little lower voltage and hence below the possible Pmax). The MPPT operating range for the batteryless model is 120V to 240 which means my four panels barely above.

Perhaps most folks putting together a system don't analyze the situation critically as I have done and just plunge forward.

Thank you.
 
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