SauRoN's SomeWatt Solar Install

Pixies said:
Redundancy. Also, what's the max V the MPPT can handle on input?
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425V if I’m reading it right.

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Redundancy does make sense though. But I’m of a mine in thinking here of something dies I switch it to grid and call someone to sort it out either which way.
 
SauRoNZA said:
@itareanlnotani @RonSwanson

Considering I have 14x450W all North facing in play would it make sense to load it all on one MPTT now and leave the other one blank until such time I want to add another direction?

Or is there a benefit I’m gaining by spreading it across MPTT’s with the two sections of roof in separate strings and rather changing it later should the need arise?
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Whats the VOC of your panels? That + maxV on MPPT will guide you. Never go above rated V as smoke will appear, Amps is fine though
 
Mzezman said:
Whats the VOC of your panels? That + maxV on MPPT will guide you. Never go above rated V as smoke will appear, Amps is fine though
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Opt. Operating Voltage (Vmp):41.1V

Opt. Operating Current (Imp):10.96A

Open Circuit Voltage (Voc):49.1V

Which one is more relevant?

So seems I would be 1 or 2 panels over depending. Would it make sense to in the future “re-balance” it and take 1 or 2 panels over to the other direction and then span it across the two MPTT’s?
 
IMHO, the chance is high that you won't find the same panels when you upgrade. The 8kW Sunsynk does 22A per MPPT so I would do 2 strings of 7 on one MPPT then it doesn't matter if you get different panels for the other MPPT. Not sure about balancing MPPT's, would like to hear the logic if this is a thing. I would assume they're independent from each other.
 
SauRoNZA said:
@itareanlnotani @RonSwanson

Considering I have 14x450W all North facing in play would it make sense to load it all on one MPTT now and leave the other one blank until such time I want to add another direction?

Or is there a benefit I’m gaining by spreading it across MPTT’s with the two sections of roof in separate strings and rather changing it later should the need arise?
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If you put them all on one MPPT you will probably make the MPPT lose its magic smoke. Nothing over 500V for the 5/8K MPPT, and anything close needs serious circumspection, you need to take into account VoC of the panels, cloud edge effect and temperatures under STC.
Rather place them in two equal strings on each MPPT.
 
SauRoNZA said:
Opt. Operating Voltage (Vmp):41.1V

Opt. Operating Current (Imp):10.96A

Open Circuit Voltage (Voc):49.1V

Which one is more relevant?

So seems I would be 1 or 2 panels over depending. Would it make sense to in the future “re-balance” it and take 1 or 2 panels over to the other direction and then span it across the two MPTT’s?
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Calculate using VoC.

I also recommend going under that about 10% as cloud effect can increase past VoC.
So 9 in series max for your panels per MPPT input

You could also go 9S2P if you wanted, but I'd recommend balance loads between the MPPT's vs all on one.

You have 14 panels though, so will probably need to go for the not so optimal 7S per MPPT, which is lower than the inverter likes for efficiency.
 
This reminds me of RonSwandon's law of solar panels: "In 76.92% of all first-time solar installations in South Africa, owners will add up to 25.34% more photovoltaic capacity within the first six months."

@SauRoNZA you may as well put those 10-12 extra panels on backorder now already, you will want them soon (after your first bad solar day) and they may be difficult to get hold of.

You are welcome.
 
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Alright so future forward planning is ultimately an external MPTT and no point in doing anything weird now.
 
RonSwanson said:
This reminds me of RonSwanon's law of solar panels: "In 76.92% of all first-time solar installations in South Africa, owners will add up to 25.34% more photovoltaic capacity within the first six months."

@SauRoNZA you may as well put those 10-12 extra panels on backorder now already, you will want them soon (after your first bad solar day) and they may be difficult to get hold of.

You are welcome.
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Ultimately was always the plan down the line.

But it’s more a next year or the year after down the line with other priorities first.

Sucks that the Sunsynk which does everything lose so well as a single package is limited in this regard.
 
SauRoNZA said:
Ultimately was always the plan down the line.

But it’s more a next year or the year after down the line with other priorities first.

Sucks that the Sunsynk which does everything lose so well as a single package is limited in this regard.
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The 8K Sunsynk's MPPTs are rated at 10400W. You still have 4100W to go on solar panels (and that is assuming perfect pitch and azimuth) before you max it out, and then there's the Aux with potentially another 8K. Where is the limitation?
 
RonSwanson said:
This reminds me of RonSwanon's law of solar panels: "In 76.92% of all first-time solar installations in South Africa, owners will add up to 25.34% more photovoltaic capacity within the first six months."

@SauRoNZA you may as well put those 10-12 extra panels on backorder now already, you will want them soon (after your first bad solar day) and they may be difficult to get hold of.

You are welcome.
Click to expand...
I see no lies here... give this man a steak
 
RonSwanson said:
The 8K Sunsynk's MPPTs are rated at 10400W. You still have 4100W to go on solar panels (and that is assuming perfect pitch and azimuth) before you max it out, and then there's the Aux with potentially another 8K. Where is the limitation?
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Okay so it’s 10,400W PER MPTT this is the part that wasn’t clear to me.

So I can have 500v PER STRING maximum, not per MPTT?

Then I reckon I’m all sorted.

And this would only be a minor wiring change at the unit itself right? Nothing needs to be done on the roof, with the existing strings I mean.
 
Pixies said:
Not following. You have 2x MPPTs and you can have two strings on each. Put one string of 7 on each now. Later when you get more panels, just move one string to the first MPPT and you have two strings on one (parallel) and a free MPPT for a new string or two.
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That’s clearly where I missed the bus.

And that makes my forward planning a lot simpler as I’d only get about 4kW on the east side anyway.
 
SauRoNZA said:
Okay so it’s 10,400W PER MPTT this is the part that wasn’t clear to me.

So I can have 500v PER STRING maximum, not per MPTT?

Then I reckon I’m all sorted.

And this would only be a minor wiring change at the unit itself right? Nothing needs to be done on the roof, with the existing strings I mean.
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No, it's an 8K inverter, so 10400W in total for both MPPTs :sneaky:
Maximum of 500V per MPPT, and 22A (which means that for max you will need to wire the panels (roughly) 6S2P for each MPPT for a total of 24 (don't quote me on the 24, it's a rough calc, I haven't seen the panel's specsheet).
Best to work on 5200W per MPPT.
 
AfricanTech said:
every thread like this brings me a step closer

Also, recently acquired a 3D printer and I suspect this little sucker likes electricity
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No, they're quite low power users really.
Depending what type you have - will use either light to cure or heat to melt, either way, won't be much power in use. Previous heat based ones I've owned maxed out at about 200w/hour, and thats peak. Usually will be far less.
 
SauRoNZA said:
That’s clearly where I missed the bus.

And that makes my forward planning a lot simpler as I’d only get about 4kW on the east side anyway.
Click to expand...
To repeat -

You could also go 9S2P if you wanted, but I'd recommend balance loads between the MPPT's vs all on one.

You have 14 panels though, so will probably need to go for the not so optimal 7S per MPPT, which is lower than the inverter likes for efficiency.

----

Your inverter will be happier with 9 in series of your current panel choice. When I say happier - I mean more effiicent. At 270v for 7S, the inverter efficiency will be lower.

Its at best efficiency sitting at 370w or so (which is where 9S sits).

Ideally you should have bought another 4 panels, which is something I did talk about previously - buying more panels and installing on the roof one time makes more sense to do, vs adding later, especially when its a small additional amount.

Right now you have 14 panels, so wire in 7S -> each MPPT. Later I'd reconnect those as 9S, which will probably cost you about the same amount to do as putting in 4 more panels now (i.e. doubling that cost at a later stage)

Getting someone in to reconnect, labour, mounting etc will cost more than just adding it now imho.


Who is doing your install?

This sort of thing is the first thing I'd have picked up and told the customer about - i.e. being optimal about panel usage. Yes, sometimes there are other things which influence - eg roof size, budgetary issues etc, but optimizing panel voltage for the inverter is a no brainer and should be something your installer or planner talked about and did.
 
Efficiency curve chart for the inverter (snarfed from the manual)
It's a small loss overall, but ideally you want to optimise everything.

I'm probably complaining a little too much here.
It's not the end of the world, and you have decent equipment that you will be happy with.

If you do have the chance or opportunity to add some now, push for that, if you can't right now, thats also ok.

Ultimately, you will add more generation or storage to your system, as you'll know your usage better after some actual use.

Enjoy being grid independent!


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