question

simjoc avatar image
simjoc asked

Multiplus II feeding back into grid

Hello,

I’ve a problem with my multiplus II set up and hopefully anybody can help me, or point me in the right direction.

My System:

Cerbo GX

MultiPlus-II 24/3000/70-32

3x Victron smartsolar

Batrium BMS With Lifepo4 battery’s

Victron ESS


So the Victron devices are communicating with the Batrium BMS over CAN. That is working flawlessly and when the Batrium changes the Charge Current Limit (CCL) the solar chargers are stopping feeding in power. So Victron is listening to the Batrium. Now when changing the setting to grid feed in (DC) there is going something wrong. First it takes way to long when the Multiplus is starting to feed back to the grid. Sometimes the Batrium give the message to stop charging and the solar chargers keep sending power. The Batrium BMS going to bypass mode and that’s not okay. Second eventually the Multiplus is feeding back to the grid, but what than happens is that the Victron is sending about 100watt to the battery’s the whole time. That should not happen because the battery is 100%.

I’m using DVCC @ 28.2 V and getting no errors.


Edit: One possibility for the problem is that @ 100% the victron sees a different percentage, then there is Batrium = 100.5% Victron is 99% (picture nu in the attachments)


Thanks,

Simon

screenshot-20210905-160853.jpg


ESS
screenshot-20210905-160853.jpg (325.8 KiB)
kabels-etc.png (328.1 KiB)
victron2.jpg (18.7 KiB)
nu.png (171.9 KiB)
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David avatar image David commented ·

I have similar setup and issues with dc feedin, and similar issue to 100% vs 99% display - see my post in the modifications section - it includes two videos.. let me know what you think - I will reply here again when I have some time.

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bonie-wanda answered ·

Whilst I’m not sure about the grid feedback issue, you shouldn’t worry about the 100w charging the battery when it’s already full. My old system did that and then my current system does that.

There’s a term for it. I think it’s “Float” charge. The charge state is also indicated in the inverter and/or MPPT. Don’t worry about it.

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David avatar image David commented ·

When DC-Feed in enabled, It seems that the CCL value sent by the Batrium BMS is ignored and all the MPPT current goes into the batteries rather than being inverted and fed into the grid.

Lets say the battery is 95% full and the BMS lowers the CCL from say 150a max -> 20a the MPPTS will push as much current into the batteries as they can, rather than only 20 going into the batteries and the rest going to grid via the Multi.

It's like the CCL value is ignored when DCFeedin is enabled. Its very weird - and dangerous as the CCL is IGNORED.

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simjoc avatar image simjoc David commented ·

Yes If this was for 30 minutes / one hour this wouldn't be a problem. But at sunny days /weeks it sometimes happens for 4 -5 hours. My battery's are getting hot and the bypasses even more. Eventually the system(battery) will go in shutdown.


At the attached pictures you see that the battery is full at 13.22. At 13.35 Victron stopped charging with 1600w and going back to 100-80w to the battery and the rest will go in the grid till 19.15 hour. At the third picture you see that the cell voltages getting really high.


1322.jpg

1335.jpg

The only thing I don't understand why the CVL changes from 28.1 to 28.2.


cell-voltage.jpg



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1322.jpg (98.8 KiB)
1335.jpg (96.7 KiB)
cell-voltage.jpg (92.7 KiB)
David avatar image David simjoc commented ·

Your min and max cell voltage measurements are very patcy. Mine look like this.

batteryvoltages.png

What is the limited current set to in the REMOTE tab in batrium?

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batteryvoltages.png (33.4 KiB)
David avatar image David simjoc commented ·
Also, your cells are hitting 3.68 - you should check your BATT TYPE in The Hardware -> Cell mon section of your BMS - choose LifePo4 longlife.
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simjoc avatar image simjoc David commented ·

That's because the Victron is keeping pushing energy in the battery. I'm showing a screen where it was going wrong. There is one battery cell wich is a little of to the rest of the cells, that's what is making the big difference.


The setting are on Lifpo4 Longlife


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David avatar image David simjoc commented ·
What’s the remote tab limited current setting? Maybe screen shot the remote tab in Batrium?
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