Planning a solar system

RonSwanson said:
With the Sunsynk you will need to balance the two MPPTs as per Keith Gough (Sunsynk CEO and chief techie). To achieve an optimal arrangement with only six panels is going to be very difficult, if not impossible. You ideally want a higher voltage on your strings to kickstart the MPPTs as early as possible in the mornings, and stop as late as possible in the evenings, so closest to 400V as possible. The Sunsynk's MPPT range is 125-425V, so it will only start producing power when the panels are giving at least 125V. You did not give the exact specs of the CS panels that you selected, so its difficult to say, but looking at some other CS panels, they appear to produce around 48.8V open circuit, but only 40.9V under full load (load drops the voltage). 3 in series on each MPPT will therefore initially produce 146.7V, but as soon as the inverter "combs" the load across to draw from solar, the voltage will drop to 122.7V, and cause the solar load to be "combed" back. So the MPPT will probably flap up and down, and the inverter too.

Obviously this needs to be verified with the exact model of panel that you have (mind posting it?), but not a situation that I would want to endorse. Did the person who sold you this explain it to you? You may want to consider returning the panels in favour of some panels that they do have sufficient stock of, to at least allow for a working system while you wait for the balance. I know that panels are difficult to get right now, and there is some price-gouging, but I would rather source equipment from a reputable source that knows and understand what they are selling, what the limitations are, and who can advise you on such caveats.
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Hi,

Thanks for the input.
I am definitely getting the last 4 panels to make 10 in the next week or 2. So my plan was to have 5 x 49.3Voc = 246Voc per string.

Would you still suggest one string per mppt?

Would there be any benefit to putting the strings in parallel to up the amps to 22?

Thank you
 
Steijn1 said:
Hi,

The panels are 49.3 Voc and 41.3 Vmp per panel, so yes I don't want to do 10 in series. Want to stay below 450V.
The Imp is 11A

I will add another 10 panels (if I can fit them on the other roof) later to have 9100W in total.

Thank you
Click to expand...
Thanks.
That's still going to be pretty marginal then, I am not sure when it will start, but you don't want to start producing only at 09H00 or 10H00. Remember also that the values given are typically at STC, and get worse the moment the temps go above 25 degrees. If I were you I'd look at another panel, or if you have space, more panels in series.
 
RonSwanson said:
Thanks.
That's still going to be pretty marginal then, I am not sure when it will start, but you don't want to start producing only at 09H00 or 10H00. Remember also that the values given are typically at STC, and get worse the moment the temps go above 25 degrees. If I were you I'd look at another panel, or if you have space, more panels in series.
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Would you recommend I do 9 in series for 443V on one mppt and save the last panel for the next string?
 
Steijn1 said:
I am definitely getting the last 4 panels to make 10 in the next week or 2. So my plan was to have 5 x 49.3Voc = 246Voc per string.
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Voc is peak voltage with no load, so it's meaningless to my point. The moment you add load, it goes down, how far depends on load level, up to 41.3V. 3 panels @123.9V will not work, not enough juice. 5 will work @205.3V, but what time in the morning will it start to produce? And that's at 25 degrees C, panels typically get far hotter than that, and Vmp will degrease.
Steijn1 said:
Would you still suggest one string per mppt?
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MPPTs should be balanced. If you only have 10 panels, then 5 per MPPT, and yes, at the voltages you have, definitely one series string per MPPT.
Steijn1 said:
Would there be any benefit to putting the strings in parallel to up the amps to 22?
Click to expand...
None whatsoever, this will decrease the overall voltage even more. You want to increase it, that means adding panels in series, or selecting another panel that has a higher Vmp.
 
Steijn1 said:
Would you recommend I do 9 in series for 443V on one mppt and save the last panel for the next string?
Click to expand...
Nope.
The MPPTs can take two strings each, but let's leave that alone for the moment.

As mentioned before, your inverter has two MPPTs, and the inputs to these two MPPTS need to be balanced (as best you can). That means as equal as possible. So whatever amount of panels that you buy, need to be split between the two MPPTs equally.
 
Steijn1 said:
Hi,

The panels are 49.3 Voc and 41.3 Vmp per panel, so yes I don't want to do 10 in series. Want to stay below 450V.
The Imp is 11A

I will add another 10 panels (if I can fit them on the other roof) later to have 9100W in total.

Thank you
Click to expand...
You could do 10 in series, but thats a little bit tight with max DC.

I wouldn't risk it, especially with our sun and a cloudy day, its just too close to 500v.
You're probably best off with 9 in series with those panels, and that inverter.

i.e. run them at 369V @ 11A / 443.7VOC (max voltage - comfortably under 500v)

I agree with @RonSwanson - these aren't the best panels for your situation.

You have the newer SunSynk 8k or the older model? (The newer model can do higher Amps)
 
RonSwanson said:
Voc is peak voltage with no load, so it's meaningless to my point. The moment you add load, it goes down, how far depends on load level, up to 41.3V. 3 panels @123.9V will not work, not enough juice. 5 will work @205.3V, but what time in the morning will it start to produce? And that's at 25 degrees C, panels typically get far hotter than that, and Vmp will degrease.

MPPTs should be balanced. If you only have 10 panels, then 5 per MPPT, and yes, at the voltages you have, definitely one series string per MPPT.

None whatsoever, this will decrease the overall voltage even more. You want to increase it, that means adding panels in series, or selecting another panel that has a higher Vmp.
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Thank you

That means I need 8 more panels as soon as possible
 
Last edited:
itareanlnotani said:
You could do 10 in series, but thats a little bit tight with max DC.

I wouldn't risk it, especially with our sun and a cloudy day, its just too close to 500v.
You're probably best off with 9 in series with those panels, and that inverter.

i.e. run them at 369V @ 11A / 443.7VOC (max voltage - comfortably under 500v)

I agree with @RonSwanson - these aren't the best panels for your situation.

You have the newer SunSynk 8k or the older model? (The newer model can do higher Amps)
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Book shows 22A+22A as PV input current
 
itareanlnotani said:
Also - ignore anyone telling you to buy XXX.

First, you need to identify what your usage is.
Thats your first step.

Second step
Reduce usage, as this is the cheapest thing to do.

Third Step
Solar..

It may take a couple of weeks or even months to get step 1 and 2 done, but then you're in a better position for step 3.
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Sounds like good advice.

I'm going to get a Digital Watt Meter (Kill A Watt) and go through all the devices in the house to determine what's using the most power.

I'd love to get an Efergy, but the cost of that seems quite prohibitive and most places don't seem to have stock.

The 3 phase power to the property is a hold-over from when it was a bakery. I don't think we even have anything that require 3 phase power. The wiring is old and the main distribution box seems to make a buzzing sound which the electrician could explain aside from saying that it's when the geysers kick in (although the timing doesn't match up.) Not sure what's going on there.

We'll definitely need battery backup for all the power outages and frequent dips we experience in town. Due to location if something does go wrong on ESKOM side it's normally a lengthy wait of 4+ hours, so having something to last through that would be optimal.

I'll most likely only have the budget to start putting things together after March. Just need a rough idea of what to look at and pricing point to aim for.
 
Steijn1 said:
Thank you

That means I need 8 more panels as soon as possible
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If you provide a link to panel's datasheet (pdf), and your location (for minimum and maximum temperatures) then I can work it all out for you.
 
RonSwanson said:
If you provide a link to panel's datasheet (pdf), and your location (for minimum and maximum temperatures) then I can work it all out for you.
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Thank you so very much for the help


I have the 455MS panels

I am fairly close to Springs Mall

Springs Mall
011 812 0295
maps.app.goo.gl

Google Maps

Find local businesses, view maps and get driving directions in Google Maps.
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Steijn1 said:
Thank you so very much for the help


I have the 455MS panels

I am fairly close to Springs Mall

Springs Mall
011 812 0295
maps.app.goo.gl

Google Maps

Find local businesses, view maps and get driving directions in Google Maps.
maps.app.goo.gl maps.app.goo.gl
Click to expand...

I followed the logical method described here.

Historical data for the coldest temperature at Springs Mall is pretty thin, so I had to use OR Tambo at Wunderground. Lowest temps recorded over the past 11 years at 08H00 was 1 degree C on both 6 June 2014 and 9 June 2011.

I adapted an old spreadsheet of mine, From this, it seems that, for a small system, you can safely use up to 9 of these panels in series maximum without blowing the MPPT controller. You may want to start your own spreadsheet if you are considering other panels.

1642340108800.png
 
konfab said:
You are going to need someone who can source you a big star, then you need to find some way of making it explode into a large cloud of stellar material. Once you do that, you can wait about 4.6 billion years and you will have yourself a solar system :p
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I just clicked on the title for the laughs , I really thought it was one of the numbnuts/whackos/flatearthers who started a thread in the Off Topic section.:ROFL:
:laugh:
 
RonSwanson said:
I followed the logical method described here.

Historical data for the coldest temperature at Springs Mall is pretty thin, so I had to use OR Tambo at Wunderground. Lowest temps recorded over the past 11 years at 08H00 was 1 degree C on both 6 June 2014 and 9 June 2011.

I adapted an old spreadsheet of mine, From this, it seems that, for a small system, you can safely use up to 9 of these panels in series maximum without blowing the MPPT controller. You may want to start your own spreadsheet if you are considering other panels.

View attachment 1227942
Click to expand...
That is great info.
Thank you very much
 
RonSwanson said:
Nope.
The MPPTs can take two strings each, but let's leave that alone for the moment.

As mentioned before, your inverter has two MPPTs, and the inputs to these two MPPTS need to be balanced (as best you can). That means as equal as possible. So whatever amount of panels that you buy, need to be split between the two MPPTs equally.
Click to expand...
I have 12 panels on MPPT 1 and 2 strings of 11 panels on MPPT 2 (24 panels) without any issues.

The strings on the mppt must be balanced but I don't think both MPPTs needs to be balanced. You could even just use one MPPT of you have limited number of panels.
 
AchmatK said:
I have 12 panels on MPPT 1 and 2 strings of 11 panels on MPPT 2 (24 panels) without any issues.

The strings on the mppt must be balanced but I don't think both MPPTs needs to be balanced. You could even just use one MPPT of you have limited number of panels.
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To me balanced does not mean # of panels, but electrically (wattage wise). I know that yours works well, so there may be an allowable threshold, but then again it's not me saying that, I am quoting Keith Gough. He also never stated what may happen if they weren't balanced, but I am sure that he he may have good reason for saying it, and not only once, I have heard it in a number of his training videos. I always understood it to be the MPPTs.
 
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