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3-Phase MultiPlus II ESS System with an additional MultiPlus II for battery charging

Dear Victron Fellows,

I have the following use case for two almost identical installations:

On the already existing 3-Phase ESS installation using MultiPlus II Devices, the battery should be charged in case of a grid failure and in time of insufficient PV power.

The installation already has the following devices:

  • 3-Phase ESS installation using 3 MultiPlus II 48/3000 operating in parallel to the public grid (230V)
  • 3-Phase Fronius AC PV converter connected at the critical loads AC Output of the Multis and controlled by frequency shifting (MG50)
  • CCGX
  • BYD B-Box 10.0 connected by VE.CAN to the CCGX
  • MPPT Solar Charger connected by VE.direct to the CCGX

A single phase 5kVA 230V Diesel inverter is available. It should be used to provide the power for the charger.

Is it possible to charge the battery using an additional MultiPlus II connected to the CCGX?

Can the Multi be connected to the CCGX and does it receive the relevant battery information BYD BMS information (DVCC)?

According to the following question it should be possible. And that is what I would expect and I think is the reason of DVCC.

Asking my dealer to verify the answer he told me that it is not be possible to connect the additional Multi to the existing CCGX, because the additional multi would need its own controller and needs to operate independent from the ESS system.

He suggested to connect the Multi by the relays (LINK). This would not be an preferred option for me because I would expect the charging process to be more optimal if it is controlled by the batteries BMS.

If the additional Multi can not be connected to the CCGX, would it be possible to add another Venus device and connect the CAN Bus to this device for retrieving the BMS information?

Best regards,

Martin

Multiplus-IIGeneratorBYDDVCC3 phase
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3 Answers
stxshadow avatar image
stxshadow answered ·

Hi !

i have 3 x MP2 5000 and an additional MP2 as Charger only. The 3 phase system is connected to a cerbo which is connected to a MQTT / Nodered. The charger only MP2 is connected to a Pi which is running Venus OS to. This Pi is also connected to the MQTT Node Red System. In this way i am able to read current / voltages / charge and discharge limits from the "leading" 3 phase system and use this informations to start charging and change currents on the charger only MP2.

Works without problems for nearly a year now.

Hope it helps.

Jens


1 comment
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Hi Jens,

this sounds very good to me.

Reading / writing those values directly using MQTT would be a very attractive option for me.

I just reviewed the latest CCGX Modbus-TCP registers.

Can you give me a hint which objects you use?

Do you use the following objects?:

/Soc
/Settings/SystemSetup/MaxChargeCurrent

Do you also have battery relais hard wired for enable / disable charging and used assistants?

I guess the additional Multi would also stop charging if the voltage limits are reached and in case of wrong values inside the RPi or not?

Best regards,

Martin


martin-m avatar image
martin-m answered ·

Hi Paul,

thank you for your response.

Is there a technical background why a 4th Multi can not be connected, just receiving the available DVCC information to charge the battery or just the implementation at the moment?

I think you are right, operating two venus devices will not work because the control can only bring the devices into account which are connected to it...

The possibility using the smartshunt seems to be very attractive at the moment.

Ok. So there are multiple solutions, that I understand using one additional Multi.

Maybe the cons are incorrect, so I would appreciate Feedback to correct it for other fellows.

Solution New Connections / Programming Pro / Cons
4th Multi controlled by BYDs relais

New Multi


Cons

  • Only charging allowed / not allowed are available at the new Multi
  • Charge current of new Multi does not go into account of existing System
4th Multi controlled by BYDs relais - charge information provided to the existing System
  • BYD BMS Relais to the AUX Inputs of the new Multi
  • DC wiring between battery, smartshunt, new Multi
  • Programming the Two-Way-BMS assistent at the new Multi
  • Connecting the smartshunt to the CCGX

Cons
  • Only charging allowed / not allowed information available at the new Multi

Pro

  • Charge current of new Multi goes into account of the existing system
4th Multi controlled by assistants and relais wiring - charge current goes into account of CCGX
  • DC wiring between battery, smartshunt, new Multi
  • Connecting the smartshunt to the CCGX
  • ??
  • ??

Pro

  • Charge current of new Multi goes into account of the existing system








Just for my understanding. I have in mind, that BYDs batteries having a BMS should not be charged without the information provided by the BMS.

This is the reason why I would appreciate a controlled charging of the additional Multi. In my opinion the allowed charge current should be available at the new Multi, and the information about the charge current of the new Multi should be available at the CCGX. This was what I had expected from DVCC while connecting an additional Multi by VE.BUS to the CCGX and connecting the DC side to the battery...

Can you explain which assistants would be relevant and how the response to the BYDs BMS could be done? So far I supposed that the BYD BMS can only provide information.

Best regards,

Martin

4 comments
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because you are 3 phase you cant add just one unit you have to add in steps of 3 units at a time.

NOW

If you could change to single phase then adding the 4th unit would be fine.

Note if you dont have ANY 3 phase appliances then switching to single phase MAYBE a option.

if this is the case then check with your electrician to see if this is practical


Hi Paul,

as the Fronius Converter is behind the Multis and is controlled by frequency shifting, there is a 3 Phase application which I need (either disabling "switch as group" nor switching to a single phase system is an option).

At the moment I do not see a technical restriction. I would guess it's an implementation detail why it does not work. The additional Multi only needs to act as a charger, such as MPPTs charge the battery and are controlled by DVCC. This additional multi does not have an AC-connection to the existing Multis.

Yes I understand your issue and questions, however the setup does not allow for it, so I dont see what choice you have.


now you could try feeding the multis charge output Through say a 70amp MPPT reg and thus the MPPT can be added as a solar charger. then the MPPT would control the multis charge output if you did this then I would suggest set the multis bulk charge to as hi as it will go and set float to the same value.

Just a different approach hope you dont mind the sugestion


Its a expensive option I agree w however it is a option


another one would be to install a contactor in the multis AC1 in line and use a assistant to turn K1 or K2 on and off based on voltage settings in the assistants, thus turning the contactor on and off RUFF but another work around, I dont wnow how well this would work with the batteries BMS control wise.

Hi Paul,

thank you for your thoughts. As you say it's an option and suitablest could be chosen. Often it depends on the available installation and the perspective / passion the installer has. So your thoughts could also be interesting for other victron fellows.

I started a new Thread and hoping that someone of the Victron Developers or Product Managers notice it. Maybe Guy Stewart or Matthjis Vader.

If you want you could like it, or just improve the request by your own thoughts.

Here's the link.

Thank you very much.

Best regards,

Martin

Paul B avatar image
Paul B answered ·

Your dealer is correct you cant add a extra unit outside of the 3 allready in place.

You could add a smartshunt in the output of the 4th multiplus to monitor its charge output.

and you could control it by setting up assistants on the main system to respond to BYD and assistant on the 4th unit to respond.

the best way is to add 3 more units and parallel them to the existing

The problem connecting then to a second CCGX is then which one is in control, you cant have 2 bosses, You might be able to read the data from the battery BMS are ONLY react on a stand alone basis,

or you could experiment with different approaches, others may have some better ideas

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