Hi all

I am hoping some of the experienced and well "learned" members can provide some advice.

 

I currently have an Axpert King 5k inverter with 12x 355w panels configured in a 2s6p setup. My panels are split into 3 groups for 4 (each 2s2p) due to the layout of my roof (see image below). They are all north facing and working perfectly if I look at peak power in summer at 4.2 / 4.3kw. The two sets that are installed on the garage roofs are at the same angle of elevation and the set installed on the house roof is at a far greater angle. As you can see from the image, I get shading on the 1 set of panels during the day for an hour or so in the morning but this does not seem to effect my "generation curve".

I have the opportunity to upgrade my inverter to a Sunsynk 5.5k unit but I am wondering if it is worth the effort or not. The Sunsyk would require me to reconfigure my panels into a 4s3p setup to achieve the required MPPT voltage but the inverter has dual MPPT which would potentially have a benefit on my setup.

My thought would be to either combine the two garages to one MPPT and keep the house roof on the other as this is consistently the strong set when testing or combine the two sets that dont suffer from shading leaving the one garage on it's own.


The upgrade cost to me would be between R5 000 and R8 000... The Sunsyk has a lot of nice features and benefits but I dont "need" them and dont want them if it is going to be to the detriment of my current setup.

What are your thoughts? Would changing the setup improve overall generation though the day? i.e. more generation in the early mornings and late afternoons (this is what I have read can be a positive effect of a higher voltage setup) or am I wasting my time?

Thanks in advance

Jason

 

 

Looks like your panels have 9A Imp, which means that even 2p on a single MPPT will be over the 13A limit (IIRC the Sunsynk is up 13A from 11A in the datasheet). So ideally, you would have to rearrange your panels so that they are 2 strings of 6, each on it's own MPPT. then it would make sense. That likely means that you also have to rearrange them on the roof for it to make sense ITO shading and angle.

Personally, I would upgrade to the Sunsynk for that price and rearrange the panels (if possible) just for the ability to power non-essentials from PV (like the geyser). If you were to step it up to a 8kW Sunsynk, you could have 2 strings on one MPPT and one string on the other (up to 22A per MPPT).

Looking at what % of PV goes wasted on a lot of installs due to low load during the day and people indicating their batteries are full at 10h the reply from P1000 to go for a Sunsynk also gets my vote. A major plus to be able to use PV for the whole installation than only for those loads that can be fed from an inverter.

@P1000... Thank you, I had not thought about the AMP limit... I was primarily focused on voltage and this has not enlightened me to more problems.... So yes, we are looking around 9A. Unfortunately moving the panels around is not an option but reconfiguring the wiring is. I could look at a few different options but dont know if I would get any generation gain from this

1 - Wire 2 sets into 1 string of 8 panels in series... This would give me enough voltage and the amperage would remain at 9. The issue here comes in is the 2nd string would only have a Vmp of around 134V and while the MPPT range is 125 to 425, the startup voltage. is 150V and I am worried the 2nd string / MPPT would struggle on a good day.

2 - Split the one set on the garage roof as this where the inverter is housed, so it makes sense from a cabling perspective. We then run 2 sets of 6 panels in series each... This would provide both with enough voltage and keep the amps at 9A. The issue here comes in is shading and the effect it has on panels in series vs parallel and I am worried that the negative effect here will outway the benefit of having 2x MPPT's

 

To answer both you and @Scorp007... My utilize around 80% of generation in peak season as my geyser is always on the system. They bypass would be used for Aircon units potentially in summer but the main aim is to improve overall generation out of peak season. So they bypass is not the main reason for change but rather the better inverter, dual MPPT, and then bypass & software.

Thoughts?

1 hour ago, Jay-Dee said:

1 - Wire 2 sets into 1 string of 8 panels in series... This would give me enough voltage and the amperage would remain at 9. The issue here comes in is the 2nd string would only have a Vmp of around 134V and while the MPPT range is 125 to 425, the startup voltage. is 150V and I am worried the 2nd string / MPPT would struggle on a good day.

To answer both you and @Scorp007... My utilize around 80% of generation in peak season as my geyser is always on the system. They bypass would be used for Aircon units potentially in summer but the main aim is to improve overall generation out of peak season. So they bypass is not the main reason for change but rather the better inverter, dual MPPT, and then bypass & software.

Thoughts?

Without all the details around load and generation even if the geyser is always on surely at some stage it will be at temperature and no longer use any of the PV.

I notice you work with Vmp. In order to get the MPPT to start you only need the above 150V to start which is early in the morning. If I look at my panels in series I currently get up to 214V early in the morning on a different system. By the time genration really starts at 08h20 - 09h30 the voltage drops to 170V as per the graph.

Yes you are marginal but if you do the connection changes yourself you might try it out. Yes shade is a problem for series and here only you would know how bad it is. At times I also only get 20% output from a string when branches grow longer and normally one only become aware of it if the PV generated is down from the norm. With me it only lasts about 6 weeks but I tend to trim when I am aware of it.

I do belief the dual MPPT has major advantages and with the software settings it is worth it in the long run.

Details of my voltage at the moment.