Sunsynk to Blue, what do I need to consider

I guess @plonkster prediction came true for me. Not because of the Sunsynk failing though but rather because I’m getting a hand-me-down from Bro.

I currently have 2x Sunsynk 5kw inverters coupled with about 42 kWh of pylontech

Have 4 strings of panels as follows with only a west facing tile roof. Other panels are mounted on the wall on brackets.

East 8x420 Canadian poly. 3360w

West top 8x390 JA 3120w

North 9x460w jinko 4140w

West down 8x360w Canadian 2880w

Total 13500w

As panels are dirt cheap now, I plan to change the 2 west strings and the east string and maybe add another 5 panels on a separate north tilted string on the tile roof. My current north string is on 2 different sections, 1 4 panels and the other 5 and have Tigo optimizers on them due to shading. At different times of the day. .

Bro currently has 3x 10kva quatro together in 3 phase with pylontech and he is changing to sigen.

He didn’t have any panels on his Victron. I will get 2 of the quatros together with the gx.

What else do I need to replace the Sunsynks? What’s the advantage / disadvantages of dc vs ac coupled. I was thinking of adding both.

For DC, the RS mppt look nice and I wouldn’t need t split my strings but they are also expensive.

For AC coupling, what’s the best option.

With the pending Eskom registrations / disconnections / fines, I’m also thinking about a full off grid system together with a generator. For most Sept 24 - May 25, I hardly used any Eskom. Winter heating is always a problem but I’m experimenting with a water to air heating system. Heat water during the day and then use that for space heating at night. If it works then freezing water in summer days and using it for cooling also becomes an option.

So firstly, what’s the best options to complete my migration to Victron and what should I look out for.

The cheapest option is to keep the Sunsynks and use them as PV chargers…

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As I am changing my panels too, the Sunsynk can only do 13A per mppt so that’s going to limit things a bit.

By how much? Enough that it is going to matter?

I have a similar issue with a Solis inverter that cannot quite convert the peak of the PV (but it is within the max spec), so I lose about 300W or so on the noon peak. I decided it is not worth spending heaps of money on to get that back :slight_smile:

Outside of that, The Victron world is pretty simple really. You have 250V units, and the 450V units. And you have to decide whether you want to rewire for 250V, or pay slightly more for the 450V unit.

For AC coupling, depends on whether you can feed excess into the grid. If yes, then you can use anything that uses frequency scaling to reduce power. If you need to grid limit, then since the latest GX firmware version (v3.60), there is support for a lot more inverters. The top two remain Fronius and Fimer (formerly ABB).

A Fronius inverter will probably cost more than an RS450, so I would probably not go that way.

Solis/Ginlong apparently does support Sunspec these days, but it is unclear if they support limiting. I’d love to know. Because that would be a cost effective way to go about it.

SMA and SolarEdge are both supported for limiting now. When correctly configured and all that. But neither of them are cheap either.

Oh, and of course you need something like a Cerbo GX to control things and log the data to VRM.

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If you’re already planning to go offgrid, why even bother with AC coupled PV? You’ve got the panels so I would say get some Smartsolars MPPT’s, even smaller one’s, one for each array and wire the strings accordingly.
If my maths are correct, each array can use a 150/70 Smartsolar with either 3s3p or 4s2p configration. Wiring wil depend on what you currently have installed and what the distance is from your equipment.

I’ve got 4 strings of 3 x 330W canadians pointing North running through a 150/70 Smartsolar and it’s been producing good power for more than 4 years now, peaking at 70Amps often on cool summer days.

I recently added 3 x 545W panels West and 3 x 545W East, each array using a 150/45 Smartsolar MPPT. Angle on all arrays around 35deg so quite low. The extra arrays increased my monthly winter production with approximitely 240Kwh, compared to the same timeframe last year and the year before.
I guess this will increase even more with summer months coming.

What I’m trying to say is that you don’t necessarily need to used huge expensive MPPT’s to do the job and you’ll probably be able to get away with smaller units coupled to each array.

That’s only my armgat mechanic opinion :rofl:

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For some reason I thought the current is a lot more than 13A. Maybe I was looking at the Isc. Imp is actually 13.6A so if the Sunsynk specs are correct, I only lose about 0.6A so roughly 25w per panel. But I remember before the firmware updates, the rated max current was 11A but my inverter would cap it at 10A. Will be replacing my panels over the coming weeks before I get the Victron kit so will be able to check it on the Sunsynk.

I currently don’t feed in as I have a smart meter and haven’t registered or changed to a bidirectional meter.

Something that just occurred to me today is that I’m probably going to need to rewire my DBs again. Does Victron have a zero export capability where it can feedback to the non essential loads like geysers which are still on the grid side? I assume this can be controlled with the ET meter and the GX

That’s my long term plan but winter and a few rainy days in summer my problem. So I need to make sure I can cover everything before I can tell Eskom to take their cable.

When I talk about AC coupled though, I’m referring to a PV inverter connected to the output of the Quattro. Dc coupling means that the dc power needs to either get stored in the battery and / or converted to AC by the Quattro. I’ve also heard that the mppts run relatively hot and the Victron inverters also derate with heat. With ac coupling, there’s less stress on the Victron inverter as the PV inverter converts directly to AC which is directly used by the loads. So ideally, the dc coupling should be used to charge batteries during the day and the AC coupled to power the ac loads directly during the day.