Match correct PV with inverter/mppt

Hi, first post here but I had friend recommended as many well informed people assisting on this forum.

Have existing Sunsynk 5kW installation - looking to add some PV solar now.
I note question has been ask many times previously - but here goes anyway.

Inverter specked to allow for:
Power: 6500W
Voc: 500V
Imax: 13A

Want to add 545W panels in config of 8 in each of strings:
iow: 8 x 545W per string

which should be within Voc of 500V (398V)

Some installers indicated that Imax on panels is to high and damage mppt (rated at 13A)

I dont agree as only important thing should be Voc to be below spec - Current is controlled as needed my mppt thus cant damage mmpt.

Am I wrong in this understanding?

thank you.

The inverter has a max Isc rating of 17A, so those panels will be fine.

Thank you for your response @_a_a_a - That is how I understood it also - but some installers seems to addiment it would cause problems - it seems there might be misinformed people.

As I understand it the installers are looking at the “Max. PV Input Power” specification of 6500W and comparing that to 16 x 545W = 8720W, and panicking.

Assuming you’re under 500V Voc and 17A Isc, Is there anything special about Sunsynk inverters that one needs to be aware of when overpanelling?

Any MPPT, on a cold cloudy day with cloud effect, may have some disastrous consequences.

Do the calcs with the Temp Coeefficent of the panels, or ask for clever people to help with that.

It is based on the lowest expected temps taken into cognizance of where you live, when oversizing, pushing the limits. I keep in mind, that the weather is changing, so warm is warmer, cold can be colder than in the last 10 years.

Yes, Voc and Isc are dependent on temperature and insolation. However, given the Voc of 398V and Isc of 13A (at STC) of the proposed design, I don’t think it’s possible to ever exceed the 500V Voc and 17A Isc limits.

The question remains: Why are installers afraid of overpanelling SunSynk inverters?

I can only speculate, titbts one may hear, stompies picked up.

Let installers rather answer. I only know how far one can go with Victron.

They misunderstand the PV input current spec. Previously SunSynk did not include the max PV Isc spec in their manual/datasheet.

1 Like

So why does Sunsynk then not just peg the Max PV Input power at a “safe” 400VOC x 17A x 2 = 13.6kWp … ? Warranty void ?

Because Voc & Isc have nothing to do with power.
Power = V x I, it only exists when both voltage and current <> 0 at the same time.
There is no power at Voc because I = 0, likewise at Isc, V = 0.

1 Like

Thank you all for the input.
Installers seems to go what their product suppliers tell them - from what I can tell.
I think installers play it very safe generally - hence issue raised about current of the panel.

A modicum of common sense has to be used.
The Voc has to be observed because that is based on an insulation threshold, and a panel produces full voltage with minimal light.

But considering the current, that’s a different ball game. For that, you need plenty of light.
Let’s take two extremes, the perfect slope and direction on a perfect day with spotless panels, well then you are probably better off following the manufacturer’s recommendation. The manufacturer has to be conservative enough in his rating to allow for this contingency.
The other extreme is if you keep your panels in a cupboard, then you can vastly exceed the manufacturer’s Isc and power rating because your panels will never achieve it.

In reality, most installations are at an imperfect slope and imperfect direction with dirty panels before long, so they are somewhere in between those two extremes.
I have found so long as the Voc is observed I can vastly exceed the maximum power recommendations of an array on a DC MPPT. I put up some panels, measure, find I still have plenty of headroom, parallel some more panels, rinse and repeat until I only have about 5 % leeway at noon on a good day.
When I parallel E and W panels I can almost double the rating and still not exceed the current rating at noon on a good day.


It is an art … with maths.

I tend to agree - I think and those “perfect” situations never exist in real life.
I have made peace now to accept 12 x 545W panels (2 strings of 6) quoted by one installer - else they wont do the job.
Pretty sure going to be way under power my inverter could handle as one string will face East and other West - but then once I have some figures might convince installer to add more panels.