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wytco0 avatar image
wytco0 asked

Multiplus-II connected battery charging from other inverters batteries

This is related to my earlier question 'Mutiplus II added to existing non Victron system'

I now have the system up an running and it is mostly working, however I have a problem that I am not sure how to correct or even if it can be corrected.

My system consists of a Growatt SPH 5000 Hybrid inverter and 4.5kw of PV and 17kwh of Pylontech batteries to which I have now added a Multiplus-II, Cerbo GX and 15kwh Seplos Mason battery.

The Victron is configured with ESS but it and the Growatt inverter are connected to separate circuits on my Consumer unit. There is no PV connected to the Victron. The Growatt monitors the grid use via a Eastron meter connected to the incoming supply and the Victon has a current transformer connected to the same tails but inside the CU.

The problem is that the Victron keeps using power from the Growatt and its batteries to recharge the Victron connected Seplos battery. This seems to happen most of the time but it is a particular problem when the Growatt has charged its batteries overnight using cheap rate electricity, as soon as the cheap rate period ends and the Growatt moved to normal running the Victron pulls 3kw from Growatt and pylontechs to charge its batteries.

Is there anything I can do to minimise this issue?


TIA

Multiplus-IIcerbo gxmultiple inverters
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Alexandra avatar image Alexandra ♦ commented ·
@wytco0

So somehow the victron is on a circuit fed by the growatt?

That points to wiring. Not much we can do here.

You can also schedule charge on the victron with ESS or node red to only charge during the cheap rates, then have a low SOC for it to draw down to at other times.

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wytco0 avatar image wytco0 Alexandra ♦ commented ·


Thanks @Alexandra

I do have a ESS Schedule set for the Victron connected battery, Its set to: Every day, 2330 (6hr 0m or 70%) to coincide with my cheap rate period.


I don't know if its possible to check but I have a feeling that the multiplus thinks that when the Growatt discharges its batteries to support grid demand, that there is excess (Solar!!) production available so it grabs it and this starts a loop where the Victron pulls more so the Growatt gives more up to its 3kw max discharge, this continues until the Victron battery is full. I can definitely see that both systems are contributing when demand is higher that the 3kw the Growatt can provide.

I am pretty sure my system is not setup optimally but I can't find out the best way to set it up, I have considered connecting the Growatt directly to the Victron but I am not sure how to do this for my system. Any ideas gratefully received.

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ejrossouw answered ·

@wytco0 Something to try. Install the MP-II CT furthest upstream on the grid incoming tails, then the eastrom followed by the house loads. This will hopefully allow the MP-II not to see any output from the Growatt system. However you will have to enable export to the grid on the Growatt to allow the MP-II to pick up excess PV once the Growatt batteries are charged. I'd am also quietly confident if the Growatt max output is exceeded the MP-II will pick up on it and support the loads accordingly.

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wytco0 avatar image wytco0 commented ·

Thanks @ejrossouw I will give that a try, I do allow export from the Growatt so this should be a simple change, the hardest bit will be getting the CT upstream of the Eastron but I can test it by running the CT cable out through a door to check if it works OK.


Any thoughts on the option of connecting the Growatt directly to the Multiplus?

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ejrossouw avatar image ejrossouw wytco0 commented ·

I am not familiar with Growatt products so cannot assist.

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wytco0 avatar image wytco0 wytco0 commented ·
OK I moved the CT to the grid side of the meter and it did make a difference but still did not resolve the issue, I now think that it could be something else and i will post another question.
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