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Can I add two more panels?


HannesZ
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I currently have 16( 8+8) JA solar 455 panels on the sunsynk SUN-5K-SG01LP1-EU inverter. Can I add two more? 

The Voc of the two 9-panel strings will be 484.83V which is under 500V(PV Input Voltage (V)) and the Max Power voltage of the panel string will be 413.37V which is less than the 425V of the MTTP.

with the 8 I am just under the 425V Voc but as the array is not at the ideal tilt i don't ever get near 6kw from the 16. 

 

Datasheet-v2.0-2.pdf

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24 minutes ago, HannesZ said:

I currently have 16( 8+8) JA solar 455 panels on the sunsynk SUN-5K-SG01LP1-EU inverter. Can I add two more? 

The Voc of the two 9-panel strings will be 484.83V which is under 500V(PV Input Voltage (V)) and the Max Power voltage of the panel string will be 413.37V which is less than the 425V of the MTTP.

On cloudy days with intermittent sun coming through your voltages may spike above the limits.
I am sure there are some guys here with a bit deeper understanding of this who could confirm if this may be the case.

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20200508101149946 (3).pdf

 

Surly it can't go higher than the Voc x9 of the panels. 

Which is 484.83V

I hopeing someone will enlighten me as from a technical point of view I don't see why this will be a problem. Only thing that bothers me is the fact that the MPPT range is 425v but I don't know if that is a max voltage or if just a limitation of the algorithm 

 

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Where is your installation located?

I assumed somewhere in Gauteng, coldest day at 2 degrees, warmest at 30 degrees. Using these assumptions, it looks to me that you are already in trouble with 8 panels per string. Assuming of course that the panels are receiving full sun on the coldest day ever.

  String size calculations          
               
  JA Solar 455W panel     Sunsynk inverter      
VoC 53.870000 volts          
Vmp 45.830000 volts          
               
              Max
      MPP 125.00 425 volts 500
      Max input DC power 6500.00 watts    
Minimum string size 2.727471 therefore    3.00 panels per string minimum
maximum string size that doesn’t exceed operating voltage 9.281604 therefore    9.00 panels per string max
Does max string size fall within MPP range 412.470000 therefore    YES      
               
Would extreme temperatures cause us to fall outside a safe operating range?                                               
Coldest day ever       2.00 degrees celsius  
Temperature Coefficient of Voc       0.27 percent    
NOCT       45.00      
Difference       43.00      
VoC * temp coefficient (voltage change /degree celsius)       0.15      
Multiplied by temp difference (what each panel will produce extra on a cold day)       6.3006352      
What each panel will actually produce on a cold day       60.170635      
All panels together 6     361.0238112      
  7     421.1944464      
  8     481.3650816      
  9     541.5357168      
  10     601.706352      
Warmest day ever?       30 degrees celsius so not over NOCT

 

 

 

Edited by YellowTapemeasure
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8 minutes ago, HannesZ said:

Western cape stellenbosch. So cloady winters with minimum of 5c.

Still pretty marginal:

Multiplied by temp difference (what each panel will produce extra on a cold day)       5.861056
What each panel will actually produce on a cold day       59.731056
All panels together 6     358.386336
  7     418.117392
  8     477.848448
  9     537.579504
  10     597.31056
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43 minutes ago, Kalahari Meerkat said:

I'd say, see it this way, if the inverter will be using the panels to produce power, you need to consider Vmp not Voc, after all, if its cold & cloudy, then your end should try an make smoke, whilst there's no excess energy to be had, and based on this thinking, you may well be safe at 9 serial panels.

That's a departure from SAPVIA Solar PV Installation Guidelines.

Edited by YellowTapemeasure
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1 hour ago, YellowTapemeasure said:

That's a departure from SAPVIA Solar PV Installation Guidelines.

Ok agree, but

6 hours ago, HannesZ said:

but as the array is not at the ideal tilt i don't ever get near 6kw

and as this would probably only ever be an issue in winter (low temperature), I'd think this should not even be an issue, @HannesZ, have you got historical data for last winter from your solar installation, I wonder, in other words, voltage measurements throughout each day, that would, in my eyes give you the information that would let you either flaunt the Guidelines, knowing it should be fine, or rather not push the limits, because voltages have been higher than one would hope for or expect...

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My system is 10 days old.... All solar is used as it is generated by my data center. What is left is feeded to my house or charger the battery and the rest will go to the grid. So I'm sure I will not cee Voc. Ever 

Edited by HannesZ
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+1 on @Vassen's Hoymiles, its the more expensive route, but safer... I would say if you don't have much or enough history to see what your panels do in winter, then safer is the betterer move, rather than taking a chance, @HannesZ, which could end up being a costly one, you can always, add the Hoymiles, with the view that as you gather data over the winter, and all looks good for you to actually take the chance on increasing the panel count on the existing strings, you could always do this then, and sell the Hoymiles and recoup some money, once you have enough data to swing your decision one way or the other.

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  • 1 month later...
On 2021/03/09 at 9:50 AM, WannabeSolarSparky said:

On cloudy days with intermittent sun coming through your voltages may spike above the limits.
I am sure there are some guys here with a bit deeper understanding of this who could confirm if this may be the case.

Yes it will, cos tour voltage will peak.

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