Hey all,

 

So busy looking into the solar panel side of the solar install I want to do and am busy working out the best way to wire everything up and which panels to go with.

I would prefer to use fewer higher powered panels versus more smaller powered panels, so leaning towards panels which are rated between 490W and 540W.

 

The inverter will be an 8KW Sunsynk inverter, so in terms of specs to be looking at would be the following:

• Solar Input
  • Max power input – 10400W
  • Max V DC input – 370V (100V~500V)
  • Max current input – 18A + 18A
  • MPPTs – 2
  • MPPT Range – 125~425V

 

So there are 2x MPPTs which can make life a bit easier. Max current is stated as 18A, however I recall it being increased with newer software / firmware. I think to 22A? Is anyone able to confirm this? @Leshen I think you mentioned this in another post somewhere on the forum.

 

As far as I understand, the ideal MPPT range for best efficiency is between 125V and 425V? Max DC input is listed at 370V but states upto 500V in brackets.

So just want to make sure I understand this, the voltage of the panels should never exceed 500V - a consideration is to calculate for cold temperatures as that will increase the voltage from the panels. I worked on cold temps of -5C which I feel is a rather safe figure to work on.

However what does one want to try aim for? Between 125V - 425V or try keep it at / under 370V?

 

Difference between the two panels spec wise (STC) is minimal, the 490W panels has slightly lower Voc of 45.33 vs a Voc of 49.45 on the 540W panels.

Imp is 12.90 for the 490W panel and 12.97 for the 540W panel. Now with either of these panels I cannot run parallel as we're then looking at over 25amps which is beyond what the MPPT is capable of (even if it 22A and not 18A).

So the way I see it, I am forced to run them in series only?

 

NOCT is 45C +- 2C and the Temp coefficient of Voc is -0.275%/C.

So for the 540W panel it is 49.6v x 0.00275 = 0.1364

The difference between NOCT of 45C and -5C is 50C

So 50 x 0.1364 = 6.82v

So 49.6 + 6.82 = 56.42v for the 540W panel

 

For the 490W panel it comes to 51.57v

 

Now if we are working on 425v as the maximum we get 8 x 490W panels or 7x 540W panels

3920W for 8x 490W versus 3780W for 7x 540W panels.

 

So if I went with the 490W panels I could get ever so slightly more power from them which would come to a total of 7840W when running 8 of these 490W panels.

 

Am I missing anything?  Is the math correct, is my understanding of wanting to try keep the volts below 425V correct or should I work on 500V being the maximum and anything over 425V just leading to lower efficiency (keeping in mind, we're working on the worst case of -5C, on average temperatures will be higher).

 

If we are working on the Voc of 45.33 (STC parameters) for the 490W, no compensation for cold temps and a max DC of 425 that means I could squeeze 9x 490W panels per string, which now gives me 4410W per string and 8 820W in total.

If 500V DC is the maximum and efficiency is simply reduced after 425V, then it would still be safe to use 9x 490W panels and majority of the time, the voltage should be in the efficient range of 125V to 425V?

Edited July 30, 20214 yr by PsyCLown

Unless roof space is a consideration, look at cost per watt also

What part of the country do you live in, coldest temperatures 

Edited July 30, 20214 yr by Tariq

The Voc is a hard limit and should not go over 500v. I'm running my one string at about 415v.

The amps can be higher without affecting the inverter negatively. The inverter will just clip the amps lower. 

Most of the newer ones sold can be upgraded by firmware add the stickers on the side would be outdated. 

So if you have the 22A version, running two strings if 12A panels, taking the total over 22A, would not be an issue. I hardly ever see my panels get the rated amps so even if yours are rated at 12A you'll probably only see 10.5 to 11A and if it did the inverter would clip it to 22A.

Thanks to @Leshen for the call.

 

So the main limit being 500V DC input, so allows more a few more panels to be installed safely.  

 

@Tariq I am in Joburg, Fourways area. It gets cold, but not as bad as other places.

1 minute ago, Achmat said:

The Voc is a hard limit and should not go over 500v. I'm running my one string at about 415v.

The amps can be higher without affecting the inverter negatively. The inverter will just clip the amps lower. 

Most of the newer ones sold can be upgraded by firmware add the stickers on the side would be outdated. 

So if you have the 22A version, running two strings if 12A panels, taking the total over 22A, would not be an issue. I hardly ever see my panels get the rated amps so even if yours are rated at 12A you'll probably only see 10.5 to 11A and if it did the inverter would clip it to 22A.

Clipping the amps would mean less output (watts) though, so bit of a waste.

 

For interest sake, does the Sunsynk have any protection regarding the 500V DC limit? Would it trip or go into a protection mode or are you then in the danger zone and at risk and your warranty void and you hope everything continues to work until it breaks?

Thinking more along the line of if cold weather hits and leads to the voltage creeping upwards.

 

 

Although, the voltage and amps would both be affected by temperature and I believe generally they are both often lower than the stated specs.

So whether one decides to run say 9x 540W panels in series or bump it up to 10 panels and do series-parallel, the likelihood of the amps or voltage being an issue is unlikely, based on the fact that typically the amps and volts are lower than what is published.

1 hour ago, PsyCLown said:

Clipping the amps would mean less output (watts) though, so bit of a waste.

 

For interest sake, does the Sunsynk have any protection regarding the 500V DC limit? Would it trip or go into a protection mode or are you then in the danger zone and at risk and your warranty void and you hope everything continues to work until it breaks?

Thinking more along the line of if cold weather hits and leads to the voltage creeping upwards.

 

 

Although, the voltage and amps would both be affected by temperature and I believe generally they are both often lower than the stated specs.

So whether one decides to run say 9x 540W panels in series or bump it up to 10 panels and do series-parallel, the likelihood of the amps or voltage being an issue is unlikely, based on the fact that typically the amps and volts are lower than what is published.

From my understand the Voc is a hard limit. The CEO has started in one of his videos that it can actually go to 550v but they spec it to 500v. The inverter also cannot clip the Voc and potentially could burn out if you exceed this limit. 

Clipping 1A to 2A should also not be to much of a waste on a 10 x 540w string. My panels are rated 9.28 and only every saw this in ideal conditions in the middle of the day in summer. 

Amps increase with solar irradiation so it starts off low as the sun rises and peaks at midday and then decreases as the sun sets so the clipping would potentially only last for an hour in the middle of the day in summer. Winter having higher rated amps is better. 

This is my one string with 9.28 rated panels only getting as high as 5.3A on a clear day in Cape Town. Voltage however does not have the same curve as amps. If I had 13A panels instead, I would have only gotten about 8A out of them so I could get more out of higher amp panels in winter and lost a bit in summer, which is actually better as I do not get enough pv generation in winter. 

Edited July 30, 20214 yr by Achmat

I specifically asked Keith ( Sunsynk ceo ) regarding the hard Voc , according to him the mppt could tolerate a maximum of 520 volts and shut down at 550 ( not sure what shut down means ), I was going to use 10 panels for a total Voc of 468 volts, but then decided not to take a chance.

 As Achmat said, you are better off with running with a bit of clipping than taking a chance with a high Voc and from what I know, doesn’t Four Ways have very cold winters

I have a Sunsynk 8kw, currently have 24 x 455W JA Solar Mono panels installed in 2 x Strings in a 6S2P config. 

VOC 53.47v and 10.56 Short Circuit Amps

Is an East/West configuration and I am getting +-40kw/hr a day and hitting a peak of 7.06kw today and averaging about 6.2kw during the day. 

Looking at my last 30 days of data

My maximum voltage is currently hitting 288V & Amps 17.3A on the West String (So no clipping of any Amps at the moment)

I am planning to add another 4 panels onto my West String and another 2 onto my East String (not enough roof space left! 

This should give me an extra +- 20% power according to my calculations which should be about 50kw/hr a day in winter, not sure what it will hit in summer as I only installed at the end of summer this year.

Good luck, look forward to seeing your data, would definitely be hesitant to go to close the the voltage limit 

22 minutes ago, Sc00bs said:

I have a Sunsynk 8kw, currently have 24 x 455W JA Solar Mono panels installed in 2 x Strings in a 6S2P config. 

VOC 53.47v and 10.56 Short Circuit Amps

Is an East/West configuration and I am getting +-40kw/hr a day and hitting a peak of 7.06kw today and averaging about 6.2kw during the day. 

Looking at my last 30 days of data

My maximum voltage is currently hitting 288V & Amps 17.3A on the West String (So no clipping of any Amps at the moment)

I am planning to add another 4 panels onto my West String and another 2 onto my East String (not enough roof space left! 

This should give me an extra +- 20% power according to my calculations which should be about 50kw/hr a day in winter, not sure what it will hit in summer as I only installed at the end of summer this year.

Good luck, look forward to seeing your data, would definitely be hesitant to go to close the the voltage limit 

Would love to see what the upgrades will do in winter as you are taking the pv to over 13kw. Mine is currently at 10.37kw with 34 x 305w Canadian solar panels and I have space to add a lot more. My one MPPT only had one string of 12 panels so I could and another string to it. The other mppt has 2 strings of 11 panels. 

So if I were to run 2x strings of 10 panels in a 5S2P configuration, based on STC parameters it would be 248v and considering the likelihood of reaching peak output being quite low, let's say I were to clip 2A to 4A that would be around 500W to 1KW roughly and only if I am reaching close to peak power output from the panels in which case I hope I would be generating at least 7KW+ at this point with the clipping which should be sufficient and not something to worry about.

 

This would also allow for 20 panels which means more power being generated earlier on in the day and later on in the evening when the sun is rising and setting and more power being generated during the winter months as well which is crucial for me - need to try reduce electricity bill each month and usage is quite high from early in the morning so the additional panels will help and also help later on as they age to produce a reasonable amount of power still.

Edited August 2, 20214 yr by PsyCLown

On 2021/07/30 at 2:11 PM, PsyCLown said:

Hey all,

 

So busy looking into the solar panel side of the solar install I want to do and am busy working out the best way to wire everything up and which panels to go with.

I would prefer to use fewer higher powered panels versus more smaller powered panels, so leaning towards panels which are rated between 490W and 540W.

 

The inverter will be an 8KW Sunsynk inverter, so in terms of specs to be looking at would be the following:

• Solar Input
  • Max power input – 10400W
  • Max V DC input – 370V (100V~500V)
  • Max current input – 18A + 18A
  • MPPTs – 2
  • MPPT Range – 125~425V

 

So there are 2x MPPTs which can make life a bit easier. Max current is stated as 18A, however I recall it being increased with newer software / firmware. I think to 22A? Is anyone able to confirm this? @Leshen I think you mentioned this in another post somewhere on the forum.

 

As far as I understand, the ideal MPPT range for best efficiency is between 125V and 425V? Max DC input is listed at 370V but states upto 500V in brackets.

So just want to make sure I understand this, the voltage of the panels should never exceed 500V - a consideration is to calculate for cold temperatures as that will increase the voltage from the panels. I worked on cold temps of -5C which I feel is a rather safe figure to work on.

However what does one want to try aim for? Between 125V - 425V or try keep it at / under 370V?

 

Difference between the two panels spec wise (STC) is minimal, the 490W panels has slightly lower Voc of 45.33 vs a Voc of 49.45 on the 540W panels.

Imp is 12.90 for the 490W panel and 12.97 for the 540W panel. Now with either of these panels I cannot run parallel as we're then looking at over 25amps which is beyond what the MPPT is capable of (even if it 22A and not 18A).

So the way I see it, I am forced to run them in series only?

 

NOCT is 45C +- 2C and the Temp coefficient of Voc is -0.275%/C.

So for the 540W panel it is 49.6v x 0.00275 = 0.1364

The difference between NOCT of 45C and -5C is 50C

So 50 x 0.1364 = 6.82v

So 49.6 + 6.82 = 56.42v for the 540W panel

 

For the 490W panel it comes to 51.57v

 

Now if we are working on 425v as the maximum we get 8 x 490W panels or 7x 540W panels

3920W for 8x 490W versus 3780W for 7x 540W panels.

 

So if I went with the 490W panels I could get ever so slightly more power from them which would come to a total of 7840W when running 8 of these 490W panels.

 

Am I missing anything?  Is the math correct, is my understanding of wanting to try keep the volts below 425V correct or should I work on 500V being the maximum and anything over 425V just leading to lower efficiency (keeping in mind, we're working on the worst case of -5C, on average temperatures will be higher).

 

If we are working on the Voc of 45.33 (STC parameters) for the 490W, no compensation for cold temps and a max DC of 425 that means I could squeeze 9x 490W panels per string, which now gives me 4410W per string and 8 820W in total.

If 500V DC is the maximum and efficiency is simply reduced after 425V, then it would still be safe to use 9x 490W panels and majority of the time, the voltage should be in the efficient range of 125V to 425V?

I don't think this one will be possible hey! You will not get more than 3K9w out of eight 490w panels 😀

On 2021/07/30 at 8:54 PM, Achmat said:

Would love to see what the upgrades will do in winter as you are taking the pv to over 13kw. Mine is currently at 10.37kw with 34 x 305w Canadian solar panels and I have space to add a lot more. My one MPPT only had one string of 12 panels so I could and another string to it. The other mppt has 2 strings of 11 panels. 

Added 4 x 455w panels this morning to my North/West string, so it is now sitting in 2P8S where it used to be 2P6S. 

As expected my amperages have stayed almost the same @ +-16.1a but my voltages increased from 266V - 367V which is spot on.

Max yesterday was 3.79kw & today was 5.06kw which is almost exactly 33% 🙂 

Should equate to about another 6-7kw/hr a day with the current winter sun.

Will only get power clipping when we get back into summer but that is not really an issue.   

On 2021/08/02 at 8:30 AM, PsyCLown said:

So if I were to run 2x strings of 10 panels in a 5S2P configuration, based on STC parameters it would be 248v and considering the likelihood of reaching peak output being quite low, let's say I were to clip 2A to 4A that would be around 500W to 1KW roughly and only if I am reaching close to peak power output from the panels in which case I hope I would be generating at least 7KW+ at this point with the clipping which should be sufficient and not something to worry about.

 

This would also allow for 20 panels which means more power being generated earlier on in the day and later on in the evening when the sun is rising and setting and more power being generated during the winter months as well which is crucial for me - need to try reduce electricity bill each month and usage is quite high from early in the morning so the additional panels will help and also help later on as they age to produce a reasonable amount of power still.

If it starts clipping @ 22A and you are sitting at 248v that would be getting 5456W out of that mppt (4464W@18A).

Either way I reckon you would probably be over 7kw total before you see any clipping. 

 

On 2021/08/02 at 9:01 AM, hoohloc said:

I don't think this one will be possible hey! You will not get more than 3K9w out of eight 490w panels 😀

I meant 2 strings of 8x 490W.

 

The clipping of the amps I do not think will be an issue, I do not need the peak output - I need more consistent output and more output as the run rises and sets - this will be far more useful and beneficial for me, so the additional panels would be welcome, although the difference is likely negligible.

Will help over time as the panels start to age and degrade.