question

mikebamber avatar image
mikebamber asked

Disabling input current limit

I have a Multiplus ii 3000 that runs in parallel with grid. So nothing connected to AC OUT - it’s used purely to charge batteries and invert battery output.


I have a problem where if over 10kw is being drawn from the grid (car charging etc) then the Multiplus won’t charge its own batteries. It did actually discharge the batteries to try to assist the grid over 10kw but I disabled it with node-red.


I understand why it does this for ‘on-line’ purposes but it seems totally unnecessary in an ESS setup.


The grid draw is measured by a CT clamp round the mains incomer.


Is there a way round this?

Multiplus-II
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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·
Can you make some screenshots from the remote console or VRM portal dashboard?

And maybe a wiring diagram would also help.

For me it sounds like the system is doing exactly what it should.

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mikebamber avatar image mikebamber Matthias Lange - DE ♦ commented ·

I will draw a diagram.


It makes no sense that the MP should throttle back it’s battery charging due to a high load being presented onto the grid elsewhere, (not thru the Multiplus). The grid is limited to 100a by way of a fuse, not 32a.

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mikebamber avatar image mikebamber mikebamber commented ·

image.jpgQuick diagram. You will see that no load is placed on the output of the Multiplus.

All I want to be able to do is draw more thank 10kw direct from the grid, and for the Multiplus to still charge its batteries, as I schedule car charging, heating and battery charging to be at the same time .

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ mikebamber commented ·

But that is exactly the purpose of ESS.

Reducing the grid usage by using energy from the battery.

ESS only charges the battery with surplus energy that otherwise would flow back into the grid.

https://www.victronenergy.com/media/pg/Energy_Storage_System/en/index-en.html

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mikebamber avatar image mikebamber Matthias Lange - DE ♦ commented ·
But this limit occurs in ‘keep batteries charged’ mode. So is there a way to raise the limit when in this mode?


I would say that a proper ESS system does not just allow surplus collection - I’m on a time of use tariff so I need to charge the batteries strategically at cheap times.

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Alexandra avatar image
Alexandra answered ·

@mikebamber

It seems like you are then missing the entire purpose of ESS. It is doing what it was designed to do.

Probably need to clear up a few things here.

it’s used purely to charge batteries and invert battery output. Help me understand this...

It inverts its output back to where? The Grid? if nothing is on its output? So you are feeding back to loads before the inverter? What is telling the system there are loads there?

The maximum feed through current is 32A as a hardware limit. It is programmed into the unit and can be told to be over ruled by remote so is adjustable. How do you have that set up?

Have you tried just switching it to keep batteries charged.

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mikebamber avatar image mikebamber commented ·

Hi, no you misunderstand what the issue is.

This is a grid tied system so the Multiplus is running in parallel to the grid supply, not acting as the supply. So it charges the batteries when there is surplus energy provided by solar and it powers the house unless I specify that I want batteries charged. In that case it pulls power from the grid.

It’s not feeding current through the Multiplus - what is happening is that the Multiplus is seeing a high load on the grid supply, and even though that load is not passing through the Multiplus, it’s acting as though it is and is limiting the charge to the batteries.



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Alexandra avatar image Alexandra ♦ mikebamber commented ·

What are the other components of the system?

How does the inverter know there are loads before itself? The grid has a CT clamp measuring at the main incomer, that I understand. But how is it integrated into the Victron system?

The feature is called power control and power assist, part of the Victron ecosystem. The only way to get it to charge if it knows there is a load to support is to switch to keep batteries charged or bump the SOC in case of grid faliure up.

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mikebamber avatar image mikebamber Alexandra ♦ commented ·
The inverter knows about the loads because of a CT Clamp over the main incomer.


I understand the input limit of the MP is 32a, but at no point is the MP input loaded with that - it’s only input is the current to charge the batteries (1800w). Remember, it’s in parallel with the grid, taking current for the batteries and feeding it back through the input. It’s there to compliment the house and act as battery storage to reduce grid draw when power is more expensive.


Other components are cerbo Gx, and two mains solar inverters. On the DC side it’s 4xpylontech us2000c.




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Alexandra avatar image Alexandra ♦ mikebamber commented ·

On the GX is the inverter metering set to the inverter or the clamp?

At this point have you told it it is allowed to drain it's batteries to load and peak shave?

It would seem as though it is receiving information where it assumes it is meant to aid the loads as there is no excess (according to its information) and is doing its job.

As @Matthias Lange - DE has said. More information is still needed here.

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mikebamber avatar image mikebamber Alexandra ♦ commented ·
I’ve just seen this.


No, this occurs when the system is in ‘keep batteries charged’ mode

I agree it’s doing the right job as if it’s got a load on the AC out - but it doesn’t have a load attached and therefore the limiting action is pointless. It’s effectively stopping me being able to charge my batteries and car at the same time.



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Alexandra avatar image Alexandra ♦ mikebamber commented ·

Confirm if this is the CT that come with the inverter? Move the CT. If that makes a difference. Then that is the issue.

Or separate the circuit for the EV so it is not passing through the CT

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mikebamber avatar image mikebamber Alexandra ♦ commented ·
Yes it’s the ct that comes with the unit

It measures the grid input accurately and also calculates the AC load accurately. Surplus energy goes into the batteries perfectly.


My issue is that the Multiplus (in ‘keep batteries charged’ mode) is limiting battery charge once the draw from the grid (*independent* of the multiplus) gets above 10kw. Seeing as my mains supply has 22kw capacity, this limiting is useless - it’s not protecting anything - it’s simply stopping the batteries charging for no good reason.



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