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Nathan Ciaglia avatar image
Nathan Ciaglia asked

MultiPlus II charge issue when external meter used.

Hi All,

I have a weird one, my installation comprises of the following components Victron MultiPlus II GX, 2 x Smart MPPT's, Smart Shunt and a 3 phase Fronius Inverter.

The Fronius is connected to the AC1 input, the loads I want to run off batteries are connected to AC1 out, nothing is connected to AC2 out and the MPPT's are connected between the Multi and the Smart Shunt.

All was working ok via ESS, however I purchased a Victron 3 Phase Meter and installed it to see how this would change the way the system operates now that it knows exactly what happening. If I leave the setting in ESS to use the Multi for the metering everything seems ok however the Multi doesn't use the Fronius power at all, this is all exported. The batteries only get charge by the MPPT's everything else seems to work as expected.

If I change the setting to use external meter I notice a few, what I think are strange things and one good. The first thing I noticed was that the Multi had started to utilise some of the Fronius power to also charge the batteries, which I though was great as they are the priority over export.

The second thing I noticed was that in the evening when we turned our 3 phase air-con on, the Multi would try to assist one of the phases by supplying power out its input AC1 in from the batteries, which isn't what should happen as this is why its connected on the input side and not the output.

The third thing I notice was also toward the end of the day when the batteries were full, the Multi would go into alarm because the voltage of my 48V system had gotten up to 60V. Using lithium ion batteries I found this to be very concerning. The other thing that happened at this point was the Smart Shunt would indicate a 15% difference between the top and bottom sections of the battery bank.

The other thing I thought was unfortunate was the inability to export excess DC.

Would love to hear anyone else that has had similar experience in these issues.

Regards,

Nathan

Multiplus-IIESS
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5 Answers
shaneyake avatar image
shaneyake answered ·

To comment on your questions:

1. This is correct behaviour, grid meter will see that you are exporting and use that power to charge the batteries.

2. This is correct behaviour. When you have a grid meter the ESS control switches from the Multi to the grid meter, meaning that if your ESS setpoint is at 0W, the multi will try keep the grid meter at 0W. This is normal behaviour for Self Consumption as the system is try to reduce the total energy you are buying from the grid. There is also no way to change this without running in ESS Mode 3 but that requires external control, Like NodeRed on the Large Firmware.

3. This is not good... Something isn't configured correctly, Most likely your Multi but possibly MPPT too. Does your battery have a BMS? Does this BMS have a CAN bus communication to the GX?

You will definitely be able to export excess DC, most likely something is wrong with your Multi configure, because it should have exported all power when your DC Bus got to the max voltage you have set in the ESS then the inverter will export.

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Nathan Ciaglia avatar image
Nathan Ciaglia answered ·

Hey Shane,

Yeah I think its great that the system can use the power from the Fronius back through the Multi to charge my batteries. The thing I wasn't keen on was the system using the batteries to supplement a phase of my Air-con that is on the input side of the Multi.

Being that I only have the Fronius ac coupled on the input of the Multi and the DC coupled on the battery, I have everything set not to export. On the ac export setting I did because its on the input and figure the Multi is only concerned with what's on its output.

The DC I disabled because I notice issues with the batteries when export was enabled, the actual issue was that the charge current overshoots the DVCC charge current set point. The batteries I'm using are 12v / 90Ah lithium ion battery packs, each contain their own BMS but this does connect to the Multi in any way, it just for safety and to keep each pack internally balanced.

Ideally, I would like to utilise the Fronius to assist the charging of the batteries but I don't want to use my batteries to help supplement with loads on the input of the Multi. I would also like to export any additional DC but have to be able to limit the current that gets applied to my batteries.

Regards,

Nathan

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shaneyake avatar image shaneyake commented ·

Hi Nathan,


I totally understand what you want to do but this isn't possible with the normal ESS.
It is possible in Mode 3 but you will have to install the large firmware and do the logic in NodeRed.
https://www.victronenergy.com/live/venus-os:large
If you do want to go down this route, I can help you develop some of the logic.
But this an advanced feature and has a steep learning curve.

I understand that your batteries BMS don't talk to the GX but 4x 12V should only go to 56V max. You should never get to 60V. There is definitely something misconfigured in your system. You also shouldn't get overshoots, do you have a BMV or SmartShunt installed?

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Nathan Ciaglia avatar image
Nathan Ciaglia answered ·

Hey Shane,

thought I would attach some pictures of the VE configure settings, perhaps you can see something I’m missing. Yes I do have a smart shunt, only thing connected after it is the batteries and the voltage and mid point are both also connected.



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shaneyake avatar image shaneyake commented ·
No images were attached.


yes, please do post pictures of charger tab and ESS assistant setup.

Do you know if the multiplus battery monitor is turn on or off?

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Nathan Ciaglia answered ·

Hey Shane,

Yeah adding multiple photos from the phone turned out to be glitchy, please see the attached pictures.

ve-configure-1.jpg





ve-configure-1.jpg (93.7 KiB)
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Nathan Ciaglia answered ·


And here are some more;

ve-configure-2.jpg


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ve-configure-2.jpg (86.9 KiB)
ve-configure-3.jpg (88.9 KiB)
ve-configure-4.jpg (84.4 KiB)
ve-configure-ess-1.jpg (97.8 KiB)
ve-configure-ess-2.jpg (92.4 KiB)
ve-configure-ess-3.jpg (85.8 KiB)
ve-configure-ess-4.jpg (91.5 KiB)
ve-configure-ess-5.jpg (87.2 KiB)
ve-configure-ess-6.jpg (88.4 KiB)
ve-configure-ess-7.jpg (88.2 KiB)
ve-configure-ess-8.jpg (82.8 KiB)
ve-configure-ess-9.jpg (90.7 KiB)
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shaneyake avatar image shaneyake commented ·
This looks all correct to me. When your system went to 60V was it because your BMS disconnected or did it actually bring up the battery to 60V?


What is the max voltage in your MPPT set to?

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