HannesZ Posted March 9, 2021 Posted March 9, 2021 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 Quote
Yellow Measure Posted March 9, 2021 Posted March 9, 2021 What are you currently getting voltage-wise on the two MPPTs? Personally I would not, but if you do, please take a video of the inverter and post it? I have never seen a Sunsynk die before. Quote
HannesZ Posted March 9, 2021 Author Posted March 9, 2021 Why would it die? 485v is less than 500v. So the caps and the MOSFET drivers should not be damaged. Why do they write PV Input Voltage (V) 100-500V Quote
WannabeSolarSparky Posted March 9, 2021 Posted March 9, 2021 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. Quote
Yellow Measure Posted March 9, 2021 Posted March 9, 2021 The VoC is either at STC (25 degrees) or NOCT (20 degrees). Winter is coming. That is why you would need to take into account the temperature coefficient of VoC (β_Voc). Quote
HannesZ Posted March 9, 2021 Author Posted March 9, 2021 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 Quote
HannesZ Posted March 9, 2021 Author Posted March 9, 2021 Thanks @YellowTapemeasureOk will need to look in to (β_Voc) thanks. Quote
Yellow Measure Posted March 9, 2021 Posted March 9, 2021 (edited) https://unboundsolar.com/blog/string-sizing-guide If you post your panel details... AH I see you already did. Edited March 9, 2021 by YellowTapemeasure Quote
Yellow Measure Posted March 9, 2021 Posted March 9, 2021 (edited) 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 March 9, 2021 by YellowTapemeasure insert calculation Quote
HannesZ Posted March 9, 2021 Author Posted March 9, 2021 Western cape stellenbosch. So cloady winters with minimum of 5c. Quote
Yellow Measure Posted March 9, 2021 Posted March 9, 2021 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 Quote
Yellow Measure Posted March 9, 2021 Posted March 9, 2021 10 minutes ago, HannesZ said: Western cape stellenbosch. So cloady winters with minimum of 5c. Are you sure about that though, I see that CT had a low of -1 degree once in May. Quote
HannesZ Posted March 9, 2021 Author Posted March 9, 2021 At night maybe but no sub zero in town. Not in the morning. Quote
Yellow Measure Posted March 9, 2021 Posted March 9, 2021 Another way around this is to use the Aux port with another smaller string inverter, or even a micro inverter, to boost PV output. Quote
Kalahari Meerkat Posted March 9, 2021 Posted March 9, 2021 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. Quote
Yellow Measure Posted March 9, 2021 Posted March 9, 2021 (edited) 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 March 9, 2021 by YellowTapemeasure added link Quote
Kalahari Meerkat Posted March 9, 2021 Posted March 9, 2021 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... Quote
HannesZ Posted March 9, 2021 Author Posted March 9, 2021 (edited) 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 March 9, 2021 by HannesZ Quote
Kalahari Meerkat Posted March 9, 2021 Posted March 9, 2021 +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. Quote
HannesZ Posted March 9, 2021 Author Posted March 9, 2021 Make sens. Hoymiles seems like a good idea Quote
Jazzy Posted April 20, 2021 Posted April 20, 2021 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. Quote
HannesZ Posted April 20, 2021 Author Posted April 20, 2021 not if there is a load and I have 5.5kwh load 24/7 Quote
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