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mikemynis asked

Grid feed back with ESS: yes or no?

Hi, I have a Victron system just setup (2 x Multiplus II, parallel) and I am confused about if this system is feeding into the grid or not?

I do NOT want to feed energy back into the grid, but I am not sure if it's configured correctly.

This is what I see. The Grid 'block' is alternating between positive values and negative values:
Then it's 127W (meaning taking from the grid. )
The next moment it's -151W, (meaning feeding into the grid.)

Is this correct for a system that's supposed to never feed into the grid?

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It has ESS installed.

I'm also confused about why it is taking power from the grid when the sun is up and solar is generating more than enough to power the loads (and the battery is at 100% SoC).

It's my idea (and wish) to ONLY take from the grid when there is no sun and battery drops to 20% SoC. Only then take from the grid.

Please advise,
Mike

Multiplus-IIfeed-in
1712579898395.png (742.1 KiB)
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anacrhy2007 avatar image anacrhy2007 commented ·

The system will never be able to TAKE FROM or FEED BACK exactly 0W. There will always be a bit of an offset. You can match this as closesly as possible in the Cerbo setup


SETTINGS > ESS > GRID SETPOINT (If set to 50W the system will try and keep the usage from grid as close to 50W at all times)

SETTINGS > ESS > GRID FEED-IN (Turn off all feed in tabs) You can also turn on LIMIT GRID FEED IN and set it to 0 but it will still deviate a little bit to and from.

Roundabout 50W to -50W is best I've ever seen the systems fluctuate at.

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mikemynis avatar image mikemynis anacrhy2007 commented ·
Thank you for answering. the thing is that to feed back to the grid you need another contract with the electricity company, which we don't have (and don't want).


It also means that when people from the electricity company start working on the cables outside (which happens occasionally here in Spain), and they switch off the mains, my system could put dangerous voltage on the grid. That could be very dangerous for those people.

So even a little bit of feed in is absolutely unwanted.

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sharpener avatar image sharpener mikemynis commented ·

<It also means that when people from the electricity company start working on the cables outside (which happens occasionally here in Spain), and they switch off the mains, my system could put dangerous voltage on the grid. That could be very dangerous for those people.>

In this situation ESS will detect Loss of Mains and open the AC-in isolator in the Multiplus, hence isolating it completely from the grid so it will not feed in and cannot electrocute anyone.

When the grid supply is restored this will be detected and various checks are carried out. The Multiplus inverter will be synchronised to the grid frequency and phase before the isolator is closed again and the neutral-earth relay is opened, this is what the clicking noises are.

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mikemynis avatar image mikemynis sharpener commented ·
Ah, I didn't know that and it's good to know. Thanks for this update!!
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2 Answers
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Alexandra answered ·
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mikemynis answered ·

Hi @Alexandra,

Thank you for explaining. So the readings are not that accurate. That makes sense.
However I am curious about your suggestion about an AC ignore system during the day.

What's that and how does that work? Do you have any info about that?

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Alexandra avatar image Alexandra ♦ commented ·

Bits and pieces from around the forum. And from what I have also done for fun yes.

Depending on what GX you have there is a way to use the relay in it )set up for a generator timer or connect on SOC), wired to the aux relay (programmed to get a signal from the GX relay to do this) to disconnect the primary/grid relays.

There was another way to use the streetlight function on some mppts if you have one available so that it uses actual light conditions to decide when to connect.

Other ways are node red.

Or an old fashioned daylight sensor with a contactor (if you are old school).

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mikemynis avatar image mikemynis Alexandra ♦ commented ·
Interesting. I have a Cerbo GX.


So if I understand correctly: configure the Cerbo so that is toggles a relay when SoC drops for example below 20%. That will switch on an external relay/contactor to connect the grid.

And when SoC raises above for example 21%, disconnect the grid. Right?

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mikemynis avatar image mikemynis mikemynis commented ·

I found this video. Interesting. It's basically what you described. The Cerbo Relay will activate/deactivate an external contactor, which connects/disconnects the grid.

The Cerbo GX can be programmed when to do that based on the battery SoC and Quiet Hours, which you can all define. Awesome ;-)

(Just replace "Remote Generator" with "Grid")

https://www.youtube.com/watch?v=6J9_3-yZke4

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Related Resources

MultiPlus-II Product page 

MultiPlus-II Manual

Multiplus-II GX Online Manual

MultiPlus-II 230V Datasheet 

VE.Bus Error codes

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