Himal Posted April 8, 2022 Posted April 8, 2022 Hi Guys, Please can you assist me - i'm looking to get a 5kv Sunsynk inverter, a 5.5kw Hubble battery and solar panels. My monthly usage 400-500 kw units. For the solar panels i have contacted two installers and each recommended different solar panels. The one installer recommended 8 x 455 solar panels (one single string) and other recommended 8 x 540w solar panels (2 strings of 4 each). The 540w panels do produce more power and will hopefully not need to buy more panels in the future, but i have concerns that this might not be the optimal panels for the invertor. However with the 455w, i will have an extra string to full up in the future. Also if a add another 5.5kw battery in the future - would i need to get additional panels depending on the panel i choose? Not sure which solution would be the best optimal solution? would really appreciate your views and recommendations. thanks Quote
iiznh Posted April 8, 2022 Posted April 8, 2022 The inverter has a MPPT that allows for 13A while the 540W is likely to produce just under that in normal conditions. You might have some instances where it will produce more than 13A but in that case the MPPT will just clip the excess current. I would say the 540W panels are better matched to the inverter. 4 Panels series is enough to reach minimum startup of the mppt but you would get greater efficiencies to consider more on a string, I have 7 on one string and 5 on the other string due to space constraints. Quote
Buyeye Posted April 8, 2022 Posted April 8, 2022 The sunsynk is a high voltage (500volts)inverter so one string of 8 should be fine. The 540 watt panels would be my choice if they are similar in price and warranty. Quote
Himal Posted April 8, 2022 Author Posted April 8, 2022 Thanks guys - @iiznh - to confirm you running 12 540w on a 5kw Sunsynk inverter? sorry dumb question what you mean by "clip the excess current"? wont damage the inverter. @Buyeyedoes the inverter not have a 3250w max rating per mppt (thats what i was told by Sunsynk)? 8 panels will take it 4320w but the volts will only be between 320-400 , which is within the MPPT range of 120v-425v Quote
Buyeye Posted April 8, 2022 Posted April 8, 2022 (edited) 24 minutes ago, Himal said: Thanks guys - @iiznh - to confirm you running 12 540w on a 5kw Sunsynk inverter? sorry dumb question what you mean by "clip the excess current"? wont damage the inverter. @Buyeyedoes the inverter not have a 3250w max rating per mppt (thats what i was told by Sunsynk)? 8 panels will take it 4320w but the volts will only be between 320-400 , which is within the MPPT range of 120v-425v I've asked that question before I don't remember the answer, then 6 panels per mppt should be sweet spot? Edited April 8, 2022 by Buyeye Himal 1 Quote
werner.potgieter Posted April 8, 2022 Posted April 8, 2022 I would work with: MPPT1+MPPT2=6500W max 13A max per MPPT 150-420Vdc per MPPT I have 8 x 460W in series on one MPPT. Quote
Nexuss Posted April 8, 2022 Posted April 8, 2022 Yea i know someone that has only one string of 8 -540w panels and he runs at about the same voltage+- as my 8 455w panels . His setup works pretty good. Quote
Himal Posted April 8, 2022 Author Posted April 8, 2022 thanks Nexuss - that's on a 5kva inverter? to be honest i just dont want to damage the inverter, which leads to downtime if they need to fix it up. Quote
Scorp007 Posted April 9, 2022 Posted April 9, 2022 19 hours ago, Himal said: Thanks guys - @iiznh - to confirm you running 12 540w on a 5kw Sunsynk inverter? sorry dumb question what you mean by "clip the excess current"? wont damage the inverter. Clipping means the inverter will only use the max it has been designed for even if more is available. Thus the extra won't damage the unit. See it as throttling on data networks. Quote
Nexuss Posted April 9, 2022 Posted April 9, 2022 17 hours ago, Himal said: thanks Nexuss - that's on a 5kva inverter? to be honest i just dont want to damage the inverter, which leads to downtime if they need to fix it up. Yes on a 5kw Sunsynk. Quote
I84RiS Posted April 9, 2022 Posted April 9, 2022 (edited) On 2022/04/08 at 2:37 PM, Himal said: Thanks guys - @iiznh - to confirm you running 12 540w on a 5kw Sunsynk inverter? sorry dumb question what you mean by "clip the excess current"? wont damage the inverter. @Buyeyedoes the inverter not have a 3250w max rating per mppt (thats what i was told by Sunsynk)? 8 panels will take it 4320w but the volts will only be between 320-400 , which is within the MPPT range of 120v-425v If the Amps produced by the panels exceed maximum Amps that the MPPT is rated for you will not damage the MPPT, you will just not get the benefit of anything over the maximum. Exceed the MPPT maximum Volts and it is a different story, you will damage it and it will end up in smoke. Remember, in good PV conditions the panels will produce more than the rated VOC (clear skies combined with cold ambient temperatures). Best to have some headroom between the string VOC and the MPPT maximum range. Edited April 9, 2022 by I84RiS Quote
Himal Posted April 10, 2022 Author Posted April 10, 2022 @Scorp007 - thanks for the explanation, understood. @I84RiS - thanks - voltage is the main concern for the MPPT - i have created the table below which shows the VOC in different conditions (STC,NOC, -10 degrees Celsius) and 40 degrees Celsius) for a 8 panel string. Based on the results it seems the VOC will be within the MPPT range of 125v- 480v per the Sunsnynk data sheet. Does this look reasonable to you? Further is the single string of 4320w a issue? As i'm assume MPPT1+MPPT2=6500W max, the 6500w doesn't not have to be split proportional (i.e. 3250w per string). Also out of interest someone told the inverter can handle more then 6500w of panels, is that true? if so how much more can you add above 6500w? 8 panels on one string will be great as i will have a MPPT slot to use in the future, where i can pick different panels. Quote
PowerUser Posted April 10, 2022 Posted April 10, 2022 @Himal you can look at my calculation for different panel strings for the 5kW SunSynk here: Quote
Himal Posted April 10, 2022 Author Posted April 10, 2022 thanks @PowerUser - the calculations in my table are as per your formulas in the thread you shared above. Quote
Nexuss Posted April 10, 2022 Posted April 10, 2022 2 hours ago, Himal said: Also out of interest someone told the inverter can handle more then 6500w of panels, is that true? if so how much more can you add above 6500w? You could easily have 2 strings of 8 panels-540w which would give you a total array size of 8,64kw. The inverter will only produce a maximum of 6,5kw though of which 1,5kw is dc to dc. Oversizing like this only makes sense if you have one array facing east and the other facing west . Check out my sig , my arrays face east and NW . Quote
Himal Posted April 10, 2022 Author Posted April 10, 2022 cool thanks @Nexuss. My panels will be facing north - so i could probably do 8 x 540 panels = 4320w (within the MPPT voltage range) instead of 2 strings of 4 panels and i will do 2180w on the second MPPT in the future to reach the 6500w. Please let me know if you guys have any other aspects i need to consider - its been a great help! Quote
Yellow Measure Posted April 10, 2022 Posted April 10, 2022 3 hours ago, Himal said: cool thanks @Nexuss. My panels will be facing north - so i could probably do 8 x 540 panels = 4320w (within the MPPT voltage range) instead of 2 strings of 4 panels and i will do 2180w on the second MPPT in the future to reach the 6500w. Please let me know if you guys have any other aspects i need to consider - its been a great help! Take the guesswork out of the equation by doing a proper sizing exercise, on a spreadsheet. https://unboundsolar.com/blog/string-sizing-guide Quote
iiznh Posted April 11, 2022 Posted April 11, 2022 (edited) On 2022/04/08 at 2:37 PM, Himal said: Thanks guys - @iiznh - to confirm you running 12 540w on a 5kw Sunsynk inverter? sorry dumb question what you mean by "clip the excess current"? wont damage the inverter. I'm running a 8KW Deye with the 7 & 5 on the 2 strings with 460W panels (have limited sun on my roof due to 60 year old trees that I do not want to cut down, they keep the house nice and cool during hot summer days. Friend of mine is running 540W strings on 5 KW Sunsync (2 inveterters in parralel) with great success and with very little clipping of current. The reason I say you need more than 4 panels in a string is when one panel is partially shaded the bypass diode will bypass the shaded area leaving you with a lower voltage which means that you might be below the startup voltage of the MPPT and effectively get 0 power for that time from the affected string. The efficiencies of converting 380V from the panels to your 230V AC is also much better than converting 160V DC to 230V AC. 4 Panels might work, but 6 - 8 will deliver power with fewer losses in the conversion process (and you will get more bang for buck from the panels you bought) Edited April 11, 2022 by iiznh Nexuss 1 Quote
Himal Posted April 12, 2022 Author Posted April 12, 2022 thanks @YellowTapemeasure - the table i shared above are as per the calculations from the link you provided. For 8 panels the max VOC is 435v at -10 degrees and 275v at 40 degrees. I'm definitely within the MPPT voltage range. Learnt alot over the past week. @iiznh agreed - i'm going with 8 panels on one string to maximum the efficiency and i got a string available for future upgrades (hopefully not needed). Guess got to wait 4 weeks now for the installer. Yellow Measure 1 Quote
Nexuss Posted April 12, 2022 Posted April 12, 2022 Something else to consider is that while 8 panels on one string will work ,there are efficiency benefits to using both MPPT's. So Ideally you want the same amount of panels on each MPPT. Between 6-8 panels on each MPPT is what i would recommend 5 absolute minimum. Quote
Himal Posted April 12, 2022 Author Posted April 12, 2022 cool - but i will only use the other MPPT if i need more solar capacity in the future and if so i can just add 5 panels to the second string to realize the efficiency. is the efficiency benefit significant when use two MPPT instead of one? Quote
iiznh Posted April 12, 2022 Posted April 12, 2022 7 hours ago, Nexuss said: here are efficiency benefits to using both MPPT's. So Ideally you want the same amount of panels on each MPPT Please explain this as I cannot understand the physics/electronic benefit? If panels all face the same orientation why put them on 2 MPPTs? Their maximum power point will all be similar and the Sunsync manual states optimal operation voltage to be 380V. Why do you need to same amount of panels on both MPPTs? You will have 2 voltages eg. 190V (13Amp eg few large panels) and 380V (6Amp eg many smaller panels) that both need to be converted to the same 220V AC. Please explain why the same amount of panels increases efficiency. I am only aware of the optimal voltage and would like to understand. Quote
Nexuss Posted April 12, 2022 Posted April 12, 2022 15 minutes ago, iiznh said: Please explain this as I cannot understand the physics/electronic benefit? If panels all face the same orientation why put them on 2 MPPTs? Their maximum power point will all be similar and the Sunsync manual states optimal operation voltage to be 380V. Why do you need to same amount of panels on both MPPTs? You will have 2 voltages eg. 190V (13Amp eg few large panels) and 380V (6Amp eg many smaller panels) that both need to be converted to the same 220V AC. Please explain why the same amount of panels increases efficiency. I am only aware of the optimal voltage and would like to understand. Keith mentioned it in one of his youtube training videos ,i honestly dont know exactly how it works but from observing my voltages/amps from my 2 balanced strings i can definitely see it does some sort of balancing of the MPPT's early morning/late evening and on cloudy/overcast days. He would probably be able to give you an in depth answer to that. Quote
iiznh Posted April 12, 2022 Posted April 12, 2022 (edited) 2 hours ago, Nexuss said: Keith mentioned it in one of his youtube training videos ,i honestly dont know exactly how it works but from observing my voltages/amps from my 2 balanced strings i can definitely see it does some sort of balancing of the MPPT's early morning/late evening and on cloudy/overcast days. He would probably be able to give you an in depth answer to that. Thanks for pointing me in the right direction. I only watched a few SunSync training videos, still have a lot more to go through. Here is a link to anyone wanting to learn https://www.youtube.com/playlist?list=PL9F1Vh3R1T5erUjksHsIj2Sttz8QuR1S3 Edited April 12, 2022 by iiznh Yellow Measure 1 Quote
Scorp007 Posted April 12, 2022 Posted April 12, 2022 5 hours ago, Nexuss said: Keith mentioned it in one of his youtube training videos ,i honestly dont know exactly how it works but from observing my voltages/amps from my 2 balanced strings i can definitely see it does some sort of balancing of the MPPT's early morning/late evening and on cloudy/overcast days. He would probably be able to give you an in depth answer to that. I think this statement comes from the fact that it is mentioned not to have different strings connected to the MPPT. You can have different number of panels to each MPPT as they are combined in any case. It is in this context that inefficient is mentioned. Quote
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