Hi all Sunsynk / Deye experts,

I'm doing a design for my house. I can fit 18 x 470W panels on my roof facing North. All would be fine if I stopped there (2 x 9S strings).

But I want to add 6 more panels facing East to increase the overall generation capacity, I can really benefit from additional PV.

The Deye 8kW supports up to 10,800W PV input in total. I was wondering if I could do the following arrangement then, which according to the specs is within limits:

MPPT1: ~8,460W - 2P9S (Imp = 22A, Vmp = 385V) 18 panels facing North

MPPT2: ~2,820W - 6S (Imp = 11A, Vmp = 256V) 6 panels facing East

Big question is, can I push the >8kW through one MPPT? Or is there a max on the overall power I can push through a single MPPT. This is not mentioned in any spec sheet as far as I can see.

Thanks

 

 

If I'm not mistaken the Sunsync/Deye 8kW has 2 MPPT's but 4 strings, have you considered that or is your 2P92, 2 strings of 9S panels each? You can split your 18N facing panels across 2 MPPT's.

35 minutes ago, mneeth said:

2P9S

 

Edited October 28, 20223 yr by FixAMess

42 minutes ago, mneeth said:

Hi all Sunsynk / Deye experts,

I'm doing a design for my house. I can fit 18 x 470W panels on my roof facing North. All would be fine if I stopped there (2 x 9S strings).

But I want to add 6 more panels facing East to increase the overall generation capacity, I can really benefit from additional PV.

The Deye 8kW supports up to 10,800W PV input in total. I was wondering if I could do the following arrangement then, which according to the specs is within limits:

MPPT1: ~8,460W - 2P9S (Imp = 22A, Vmp = 385V) 18 panels facing North

MPPT2: ~2,820W - 6S (Imp = 11A, Vmp = 256V) 6 panels facing East

Big question is, can I push the >8kW through one MPPT? Or is there a max on the overall power I can push through a single MPPT. This is not mentioned in any spec sheet as far as I can see.

Thanks

 

 

On your proposed mppt 1 the inverter will limit the current to 22A

6 hours ago, Chris_S said:

On your proposed mppt 1 the inverter will limit the current to 22A

That is fine, I can live with that. My installer says, in his experience, the power delivered to the MPPTs should be more balanced, ideally 5kW each per MPPT. That is what I'm worried about in my design. I've seen another member on here with a (by my calculation) 6.7kW input on one of the MPPTs @Achmat of the 8kW. Can I push it further?

7 hours ago, FixAMess said:

If I'm not mistaken the Sunsync/Deye 8kW has 2 MPPT's but 4 strings, have you considered that or is your 2P92, 2 strings of 9S panels each? You can split your 18N facing panels across 2 MPPT's.

 

You are correct, it has 2 MPPTs with 2 strings each. So I'm proposing to have on one MPPT all 18 of the North facing panels as 2 strings of 9 (2P9S, am I using this notation wrong?). If I split the 18 North facing panels across 2 MPPTs, where does the leave the East facing panels?

As far as I know you have to connect the same size strings with the same orientation for the 2 strings per MPPT.

Edited October 28, 20223 yr by mneeth

9 hours ago, mneeth said:

I'm doing a design for my house. I can fit 18 x 470W panels on my roof facing North. All would be fine if I stopped there (2 x 9S strings).

But I want to add 6 more panels facing East to increase the overall generation capacity, I can really benefit from additional PV.

That is why I went with 2x 5kW instead of 1x 8kW - to get more flexibility on the strings. The price increment for that was not that significant (when looking at the costs for the whole system)

8 hours ago, mneeth said:

You are correct, it has 2 MPPTs with 2 strings each. So I'm proposing to have on one MPPT all 18 of the North facing panels as 2 strings of 9 (2P9S, am I using this notation wrong?). If I split the 18 North facing panels across 2 MPPTs, where does the leave the East facing panels?

As far as I know you have to connect the same size strings with the same orientation for the 2 strings per MPPT.

That is a large input on 1 mppt and smaller on the other input. I also wanted to use 2 x 5kw inverters so I could have 4 mppt's but just settled on an 8kw instead. I don't know what your requirements are but maybe 9S on each mppt will be enough PV for you? 

I have also seen micro inverters being used and more PV fed into the GEN port. 

 

Do you have a West roof? 

Why not do 9S panels north and a 6S2P east/west split? 

Or 6S2P North on 1 mppt and

6S2P east/west on the other mppt

That should balance it better. 

Thanks @Chris_S @wolfandy@FixAMess for your suggestions.

I've also considered the case for 2 x 5kW to have 4 MPPTs, much more flexibility as you say and that will most likely be the way to go.

I'll re-asses the west facing roof, I do like the idea of having a bit of late-in-the-day generation capacity.

Quote

I don't know what your requirements are but maybe 9S on each mppt will be enough PV for you?

Why have 8kW when you can have 11kW 😂. I use a lot in a day >55kWh, but roof space is a bit limited.

One thing I'm wondering about is the home assistant integration with a 2 x inverter setup. Will the 2 Inverters show up as a single one? Probably not that important, as long as I can see the total coming in from the grid and the SOC of the batteries. I want to try dynamically enable/disable loads using automation to optimise the power draw from the grid.

20 hours ago, mneeth said:

Hi all Sunsynk / Deye experts,

I'm doing a design for my house. I can fit 18 x 470W panels on my roof facing North. All would be fine if I stopped there (2 x 9S strings).

But I want to add 6 more panels facing East to increase the overall generation capacity, I can really benefit from additional PV.

The Deye 8kW supports up to 10,800W PV input in total. I was wondering if I could do the following arrangement then, which according to the specs is within limits:

MPPT1: ~8,460W - 2P9S (Imp = 22A, Vmp = 385V) 18 panels facing North

MPPT2: ~2,820W - 6S (Imp = 11A, Vmp = 256V) 6 panels facing East

Big question is, can I push the >8kW through one MPPT? Or is there a max on the overall power I can push through a single MPPT. This is not mentioned in any spec sheet as far as I can see.

Thanks

 

 

Hi @mneeth

10400w is the maximum DC power that the inverter can produce, it is not a limit to the amount of panels you can put on the inverter.

The inverter can produce a maximum of 8.8kw of AC power so any more than that produced will need to go into the batteries. 

Maximum Amperage the MPPT will use is 18A and maximum voltage is 425V, I would give the 425V limit a wide berth as panels can spike the voltage if they are very cold, you should be good at 385V so your North facing string is 385V x 18A = 6930Watts

You could either add extra panels to your East facing string if you wanted or maybe go for a higher amperage panel.

The big restriction on the MPPT's is the Voltage which you must be careful not to go above.  The inverter can control the amperage the panels produce by increasing the resistance in the inverter which reduces the amperage/power being produced. The inverter also reduces the power being generated from the panels when the batteries are full and there is no where for the power to go. The guys from Sunsynk talk about over watting the panels.

I have 12,740 watts of panels on my 8kw Sunsynk for example. 

Makes more power than I can use on high solar radiation days but most important thing is on overcast days it still makes enough power for us to charge batteries and cover all my day time usage. 

15 hours ago, mneeth said:

That is fine, I can live with that. My installer says, in his experience, the power delivered to the MPPTs should be more balanced, ideally 5kW each per MPPT. That is what I'm worried about in my design. I've seen another member on here with a (by my calculation) 6.7kW input on one of the MPPTs @Achmat of the 8kW. Can I push it further?

This is more of an issue with the Voltronic inverters from what I understand

22 hours ago, FixAMess said:

If I'm not mistaken the Sunsync/Deye 8kW has 2 MPPT's but 4 strings, have you considered that or is your 2P92, 2 strings of 9S panels each? You can split your 18N facing panels across 2 MPPT's.

 

The strings have to be the same voltage if they are sharing the MPPT though, so just saving 2 x T's for your parallel strings but you have to have longer cables. 

32 minutes ago, mneeth said:

Thanks @Chris_S @wolfandy@FixAMess for your suggestions.

I've also considered the case for 2 x 5kW to have 4 MPPTs, much more flexibility as you say and that will most likely be the way to go.

I'll re-asses the west facing roof, I do like the idea of having a bit of late-in-the-day generation capacity.

Why have 8kW when you can have 11kW 😂. I use a lot in a day >55kWh, but roof space is a bit limited.

One thing I'm wondering about is the home assistant integration with a 2 x inverter setup. Will the 2 Inverters show up as a single one? Probably not that important, as long as I can see the total coming in from the grid and the SOC of the batteries. I want to try dynamically enable/disable loads using automation to optimise the power draw from the grid.

You could also just add a grid-tie onto the Aux port for up to 3kw extra

Great, thanks for all the extra info @Sc00bs.

1. I'd need to do the cost calculations for micro-inverter or other small inverter for the 3kW Aux port but yes, that is also under consideration. What small 3kW inverter would you suggest for the Aux route?

2. The panels I'm looking at (JAM72S20) are 11A nominal output (So can't really get to 18A) and the MPPT on the Sunsynk 8kW can handle 22A each, not 18A. So 2 parallel strings works out perfectly I thought. With 9 panels per string, the Voc maxes out at 490V at -5C which I think is ok for Johannesburg. If you think that is too close to the limits, i could drop a panel per string and then we are looking at 2P8S = 7520W for MPPT1.

17 hours ago, mneeth said:

As far as I know you have to connect the same size strings with the same orientation for the 2 strings per MPPT.

Yes, makes sense.....It would be interesting to see the effect of not having the 2 strings balanced......

2 hours ago, mneeth said:

Great, thanks for all the extra info @Sc00bs.

1. I'd need to do the cost calculations for micro-inverter or other small inverter for the 3kW Aux port but yes, that is also under consideration. What small 3kW inverter would you suggest for the Aux route?

2. The panels I'm looking at (JAM72S20) are 11A nominal output (So can't really get to 18A) and the MPPT on the Sunsynk 8kW can handle 22A each, not 18A. So 2 parallel strings works out perfectly I thought. With 9 panels per string, the Voc maxes out at 490V at -5C which I think is ok for Johannesburg. If you think that is too close to the limits, i could drop a panel per string and then we are looking at 2P8S = 7520W for MPPT1.

Specs for the Sunsynk still say 18A but you are correct that the DEYE is 22A so better.

Max Voltage on the DEYE is 500V so I would be inclined to drop to 8S to be safe, also optimum MPPT is 125-425V 

I would also speak to the DEYE distributors and check what they say about balanced MPPT controllers,  they may have a different opinion. 

 

5 hours ago, mneeth said:

One thing I'm wondering about is the home assistant integration with a 2 x inverter setup. Will the 2 Inverters show up as a single one? Probably not that important, as long as I can see the total coming in from the grid and the SOC of the batteries. I want to try dynamically enable/disable loads using automation to optimise the power draw from the grid.

I only briefly played around with HA and SolarAssistant integration - but it showed the combined values for both of my inverters (if I remember correctly you can also read the individual values if you are interested)

1 hour ago, Sc00bs said:

I would also speak to the DEYE distributors and check what they say about balanced MPPT controllers,  they may have a different opinion.

Yeah, that's the thing, I'm not sure if the distributers will have an authoritative answer. Would like to try and find out from Deye themselves.

The MPPTs will be totally independent, so as far as I know there is no requirement or advantage to "balancing" them. The whole idea of multiple MPPTs is to handle arrays with different light levels and therefore different power throughput. 

Many people run with panels on one MPPT and none on the other with no problem. That's the ultimate unbalance. 

Thanks,

Yes I agree I may have incorrectly framed it as 'imbalance' it is more a question of can one MPPT on the 8kW model handle >8kW PV input. Usually the installers will balance a total of 8kW of input across the two MPPTs as there is no reason to push it all through one MPPT.

15 hours ago, Sc00bs said:

Specs for the Sunsynk still say 18A but you are correct that the DEYE is 22A so better.

Max Voltage on the DEYE is 500V so I would be inclined to drop to 8S to be safe, also optimum MPPT is 125-425V 

I would also speak to the DEYE distributors and check what they say about balanced MPPT controllers,  they may have a different opinion. 

 

Yes, the specs say 18A for the Sunsynk, but they increased it to 22A. Then they throttled it back to around 20-21A for "stability reasons". So if I were planning an install using an 8K Sunsynk, I would plan for around 20.5 -21A. 

51 minutes ago, mneeth said:

Thanks,

Yes I agree I may have incorrectly framed it as 'imbalance' it is more a question of can one MPPT on the 8kW model handle >8kW PV input. Usually the installers will balance a total of 8kW of input across the two MPPTs as there is no reason to push it all through one MPPT.

As long as you don't go over the max voltages on the MPPT you are ok.  

As long as there is place for the power to go, the inverter will handle up to 10400W of DC PV power

Maximum AC production is 8.8kw so the balance would go to the batteries, assuming that there is charge space in the battery and that your charge rate allows for the amount of power that the MPPT's are generating to go to the battery. If there is no place for the power to go the MPPT's will throttle the PV Panels and reduce the power being produced appropriately. 

The main reason for having more than 10400W of panels on your roof is not for the high production days but rather to allow for sufficient power generation on the marginal days. 

 

 

On 2022/10/30 at 7:54 AM, YellowTapemeasure said:

Yes, the specs say 18A for the Sunsynk, but they increased it to 22A. Then they throttled it back to around 20-21A for "stability reasons". So if I were planning an install using an 8K Sunsynk, I would plan for around 20.5 -21A. 

Interesting @YellowTapemeasure, I noticed my Deye inverter maxes out at 9kw input, and although the inverter says maximum of 22A per MPPT, at 9kw, the current from the PV is +-20A. I actually thought maybe it's a setting that I need to change but what you are saying is making sense here. So I can't really hit the maximum 10400kw at all by the looks of it 🙁

4 hours ago, isie said:

Interesting @YellowTapemeasure, I noticed my Deye inverter maxes out at 9kw input, and although the inverter says maximum of 22A per MPPT, at 9kw, the current from the PV is +-20A. I actually thought maybe it's a setting that I need to change but what you are saying is making sense here. So I can't really hit the maximum 10400kw at all by the looks of it 🙁

You should be able to still hit the maximum if you increase the voltage enough. 

The same for the 5K Sunsynk, the manual states 11A but they increased it to 13A, and then they moved it back to about 10A.

I am really not sure about Deye, but the best test is to max it out on a clear day from say 11H30 to 12H30, and charge batteries at the same time. On the production graph you will clearly see the flat top vs the curvature on the top of a bell curve. Then pull the raw stats for that hour.

9 hours ago, YellowTapemeasure said:

You should be able to still hit the maximum if you increase the voltage enough. 

The same for the 5K Sunsynk, the manual states 11A but they increased it to 13A, and then they moved it back to about 10A.

I am really not sure about Deye, but the best test is to max it out on a clear day from say 11H30 to 12H30, and charge batteries at the same time. On the production graph you will clearly see the flat top vs the curvature on the top of a bell curve. Then pull the raw stats for that hour.

Correct, if I add a panel or 2 more, that should increase the voltage and in turn would increase the power