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wytco0 avatar image
wytco0 asked

Mutiplus II added to existing non Victron system

I have an exiting system with a Growatt SPH 5000 Hybrid inverter and 4.5kw of PV and 17kwh of Pylontech batteries, this has been working well for some time.

I have now added a Multiplus-II, Cerbo GX and 15kwh Seplos Mason battery, this has been tested and is working.

The Growatt can only discharge a maximum of 3kw from batteries which means I often have to use grid power when there is lots of energy stored in my batteries. In addition I want to minimise export to the grid and use any energy that would be exported to charge the Seplos Battery via the Multiplus II.

The Growatt uses an Eastron SDM230 meter to monitor grid draw and this is located in the supplier meter area on the main incoming tails.

I believe that I need to add a CT clamp on the house side of the Eastron meter, to allow the Multiplus II to know how much it needs to discharge to match demand, or how much is available for it to charge the Seplos Mason battery.

Assuming this is correct can someone suggest the best way to set it up and which CT I should use, my unit is a 'MultiPlus-II 48/5000/70-50 230V (48V - 70A Charger - 50A)', it is approximately 5 meters away from the incoming main supply.

In addition how should I configure it to charge its batteries when the Growatt would otherwise export?

Thanks

Multiplus-IIcerbo gx
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Alexandra avatar image Alexandra ♦ commented ·

@wytco0

Are you planning on using ESS?

Do you export to grid at all?

Is the growatt on the input or output side of the multiplus? It would be better to have it on the input since it cannot control the growat. Then power assist from there.

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wytco0 avatar image wytco0 Alexandra ♦ commented ·

Hi Alexandra, sorry I have been offline for a few days.

Yes we do sometimes export to the grid but I don't want to do that as it means I am wasting production as I do not get paid for it.

The current setup is that the Growatt and the Victron are both connected to their own circuits in the consumer unit and they are not linked directly. I am not sure if its possible to set the Growatt to be an 'Input' to the Victron, how would that be done?

Regarding ESS, I don't think I can use ESS as my Multiplus II can only handle 50A and potentially my house load can exceed that. We are 100% electric with a ASHP and electric car, I think we could break through 50 amps in the winter.

Longer term I want to split our circuits so that most are wired after the Mutiplus II but I can't do that yet. Even longer term I would like to go off grid but that's not technically feasible for us yet as we use too much power.

Part of the reason for asking the question was to see if there is a better way of setting up my Multiplus and I am grateful for any ideas.

Thanks

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sharpener avatar image sharpener wytco0 commented ·

AFAIK you do not have to have the house loads connected to the AC-Out of the Multi to use it in ESS mode. Though I note your eventual plan is to move some of them there.

Meanwhile if you leave the two systems on two separate circuits and put the standard accessory CT (or a cheap equivalent from Amazon) on the incoming grid supply feeding both then I think ESS mode will

(i) treat the excess from the Growatt as if it were PV on AC-In which is a standard configuration

(ii) power assist up to its maximum output.

You will need to think how to prevent the Multi from discharging its own batteries to charge those on the Growatt. Presumably you can set the Growatt to not charge from the grid, only from the PV.

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wytco0 avatar image wytco0 sharpener commented ·
Excellent thanks Sharpener, I have just returned home from an off grid weekend at an extremely wet music festival! so catching up. I will have a proper look at this tomorrow as I think I need to ask you a follow up question, hope that's OK.
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wytco0 avatar image wytco0 sharpener commented ·
OK I have now read this properly and I think I understand it apart from the point about the CT clamp, currently I have a Eastron SDM230 meter connected to the house incoming tails directly after the DNO isolation switch, this works fine.


I also still have a CT that was originally connected to the Growat but is now just disconnected on the tails but on the CU side of the Eastron Meter. I had thought I might be able to use that CT with the Victron but its does not have the correct connection (I think the Victron uses a round plug), my question is where should the new CT for the Victron be placed? if it is in the same place as the Growatt then won't the 2 inverters both try and respond to the same usage or export at the same time and get confused?


I did a little research into CTs for the Victron, my house has 100amp supply with 25mm2 tails and I was a bit confused about what CT clamp spec I need to use? can anyone advice a good fit for my system?

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Bret Watson avatar image
Bret Watson answered ·

Coincidentally, I am looking at something similar.

In my case I'm not allowed to connect the Multiplus II to the grid :(. But I am thinking of connecting it to the "EPS" output of the Growatt 5000SPH. I note that both units support a VPP mode - and I'm curious if anyone has managed to get them to cooperate?

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wytco0 avatar image wytco0 commented ·
I can't directly answer your question but I did have a play with the EPS on my Growatt SPH-5000 and found that it is only live when the grid is down, most of the time it is not live. This may be something that can be configured but if so I couldn't see how.
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