3 Phase system with 1 phase grid connection

Q&A and troubleshooting DESS
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1

I have a working 3 phase Victron system consisting of:

  • 3x MultiPlus II 48V8000 VA
  • 3 sets of 280Ah LifePo4 batteries with BMS on each (200A)
  • 2 x SmartSolar 250/100
  • 100A smart shunt
  • Cerbo
  • Panels

That system was working perfectly for three years.

As we got the single phase grid connection with option to sell excess power to the grid, I have been advised to get 4th MultiPlus II (got the same, 48V/8000 VA)

I have to note that we have some 3-phase loads so going full single-phase was not the option.

4th Multiplus is connected to the grid (only by AC-In), has NO load connected to AC-Out, has it’s own 500A SmartShunt to the 3-phase plus and minus system busbars and has it’s own Cerbo

I want to setup the following to the grid-tied inverter:

    1. Starts transferring power to grid when batteries are 100%
    2. Stops transferring the power to grid when batteries fall to 95%
    3. Starts charging batteries from grid when batteries are 50% full
    4. Stops charging the batteries when batteries are 70% full

Also, limit pushing to grid should be 3600W.

I have tried ESS settings but it does not work as I want. I got some functionality, though.

Then I tried and connected one SmartSolar to grid-tied Cerbo and it started sending power to grid, but it was not fully functional. Quote not sure when it starts and when it stops, plus it was pushing 5kW to the grid even if I set it to 3600W max at ESS settings.

Can someone let me know which configuration and which settings to use?

Worst thing is that there is no mobile or Internet connection on site, sonI need to bring laptop and enter settings on site with no online help

2

how are the 3 older MP2 connected to grid if you only have one phase feeding the house?

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3

Hi

Three phase system is feeding the house, from the batteries. It is 3 × MP II 48/8000

Fourth inverter is the only one connected to grid. And is used for charging the batteries and send excess power to the grid.

4

why this can´t be done with just 3 inverters? what is the reason fr the fourth?

So usually you don´t need any residual power, just in special cases?

As the 4th inverter is already there you have to feed this 4th inverter with Data how to behave, what to do

Easiest would be to do a Node Red Script

Do i understand right, Inverter 4 is the only connection to grid, 1-3 have no connection?

5

Yes

It was done like this because grid is single phase and house is three pbase, with several three phase loads.

I do not have experience with Node red scripts. Any point where to look for it?

6

I just found this:

7

i don´t have such a strange system, but thinking about that:

Not even node red needed - MP2 #1/2/3 is just a consumer, MP4 #4 don´t has to know anything about them

Only thing MP2#4 needs to know the SOC of the Battery, and act as desired?

As everything is bought already, connect the 500A Smartshunt in a way that it meassures the Current of all Bateries together, knows the SOC, MP2#4 reacts to that?

you say you have 3 sets of batteries, are they all parallel or each MP2 has its own Battery pack?

8

Thanks kr0815

On the 3-phase system, which consists of 3 x MP2 , I have 1000A SmartShunt, connected to Cerbo A

On 1-phase system, which is the only one connected to grid, I have a 500A, SmartShunt, connected to Cerbo B

All 3 sets of batteries are in parallel, connected to 300 sq mm bus bars. To same bus bars are connected all other devices: all 4 MP 2s, both smart shunts, all SmartSolar regulators (3 in total)

SmartSolar regulators are connected to Cerbo A (of 3-phase system) through Ve-Can

It is a bit complicated system, but the only intention was to have it working like this:

- 3 MP2s are just consumers

- 4th MP2 is the only one connected to grid, and has to work with these parameters:

  \* export excess power to grid (above set voltage or SOC), and not exceed 3600W of power which goes to grid

  \* charge batteries when SOC drops below set point (let's say 50%), measured by SmartShunt 500A

I have tried many settings, even trying to connect SmartSolars to Cerbo2 (of MP2 4) , but for some reason the system is not acting as I (thought) I have set it.

9

your problem are the 2 Smartshunts - what should they meassure?

See the smart shunt as a water meter - there should only be one in the system

Only interesting value of the smartshunt is the SOC - you have to find a way to transfer this value from cerbo 1 to cerbo 2

This yould be done by MQTT, you need aditional software

BRW, i also have a smartshunt here, but i don´t use it anymore

I only use the SOC that is reported by the battery BMS, don´t you have a BMS for each battery pack?

10

I understood that 2 shunts are the problem and that is why I have changed it yesterday so that .ain, 100A shunt is connected to Mp2 #4’s (the one cinnected to the frud) Cerbo

Now three MP2 which are powering the house are only the consumers, and both Shunt and SmartSolar regulators are reporting to Cerbo of the MP2 connected to the grid.

500A shunt which was connected to that MP2 is still there, but not connected by the cable to any Cerbo

Today I was away but tomorrow I will check how the system works.

I have 3 BMS units, but those are 200A JK without inverter connection option (old style)

I might get comm. boards for those BMSs now, as JK made it

11

you have to many counters

one smart shunt is enough to keep control of Battery SOC

This SOC has to be

  • anounced the 3 MP2-5000 to stop when battery is empty
  • MP2#4 needs this SOC to decide what to do
12

I understand

Now only one SmartShunt is connected, but 3 x MP2 are not getting any info from it

Not sure what will happen if I connect those 3 (their Master, in fact) to the same Cerbo where grid is connected. Would that disturb the system as, as I am aware, I cannot connect twonsystems to the same Cerbo

Additionally, can I use Master’s measurement of SOC to stop using the batteries whem they are empty? I know thst is not the most accurate SOC but in this case that should not be the issue, I believe

13

My idea on this problem is use 2 gx devices and a raspberry pi with Homeassisten or something Else .

Configure on the 2 gx devices the mqtt connection and on the raspberry you Import the 2 gx devices in to one mqtt broker.

So you can write a rule to read out the main system soc and when the Soc ist at 100 percent the the 4th multi is start to feeling the grid with 3000w or less when the Soc is 98 percent then the 4th multi Shops feeding the grid.

I use a system like this to use my battery at my camper to Support the main battery at home. And i control a blueetti too.

14

theoretically you could wire the 2 smartshunts in series, but i dont know if they are insulated

i´d say this is what you need: GitHub - mr-manuel/venus-os_dbus-mqtt-battery: This Venus OS driver gets the data from MQTT and displays it as battery.

so no need for external MQTT Server, Homeassistant or such things

Simply let MP1-3 listen to the MQTT Message of MP4 or vice versa