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mikebamber avatar image
mikebamber asked

MultiPlus ii Parallel Question

Hi, currently running an MPii with 4x Pylontech US2000s. Everything is great. I don't use the AC out, it's running as a grid tie ESS. Using solar too on the AC side.

What I want to do is add a second Multiplus with a different type of battery (thinking EVE LiFePo4 cells and Batrium BMS).

If this works then I can scale the system up over time with more MPs.

Is this feasible? or do both the multiplusses need to be connected to the same battery?

multiplus in parallel
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mikebamber avatar image mikebamber commented ·
Am I overthinking this? Can I just add more Multiplus devices to the AC IN supply, hook them all up to the Cerbo and they'll be happy?
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Alexandra avatar image
Alexandra answered ·

@mikebamber

If they are being programmed as parallel then they share a battery bank.

There is some more documents and information linked in the related resources box on this page - to the right on laptop - to the bottom on mobile.

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mvas avatar image
mvas answered ·

How does the existing MultiPlus know when it is OK to recharge the battery bank? Time of day? Do you have TOU electric rates?

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mikebamber avatar image mikebamber commented ·

I manually schedule charge time, also the battery charges from surplus solar.

So can you confirm that the proposed system is OK? Would they operate effectively as a master unit and 'see' two batteries?

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Alexandra avatar image Alexandra ♦ commented ·

It is a requirement for Victron - it is in the manual.

if there is a voktage difference - if there is an amp difference - they will perform differently and not load share.

There is if they they do not share the load equally one bank will deplete faster than the other - one unit will then shut down before the other and then you will see errors on the GX - for example error 3
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mvas avatar image mvas Alexandra ♦ commented ·

What "load sharing" are you talking about? There is no load on AC OUT.

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mikebamber avatar image mikebamber Alexandra ♦ commented ·
So I'm not sure if it's relevant to your reply @Alexandra but I'm not using the AC out, just using AC in in a grid-tie config.


@mvas yes I'm on a TOU electric tariff but also I have a lot of solar panels.

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mvas avatar image mvas mikebamber commented ·
People may think that your MultiPlus will be sharing a load on AC OUT because you used the word "parallel", as in a "Master / Slave" Parallel configuration, in your title. Are going to enable "Master / Slave" Parallel mode configuration for load sharing? Do you have a Cerbo?
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mikebamber avatar image mikebamber mvas commented ·
I have a cerbo, yes.

This is why I'm asking the questions - I'm trying to find out if it is possible to make the two (or more) units act as one or whether they need to be run and controlled as separate systems. Bear in mind I would potentially like to go beyond two units.

Can I assume at least that they will happily sit on same AC supply together?

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Alexandra avatar image Alexandra ♦ mvas commented ·
Why even have the inverters if there is no load on them?

I guess we are using terminology differently here.

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mikebamber avatar image mikebamber Alexandra ♦ commented ·

@Alexandra So I'm using the inverters to enable me to use batteries. My setup is an ESS setup, so I'm permanently grid connected. My electricity rates change every half hour and I also have lots of solar panels. So I want to 'bank' electricity during the cheap periods and also store the solar. The multiplus units backfeed the AC IN when discharging the batteries.


EDIT: My install: https://vrm.victronenergy.com/installation/327623/share/3ff0dd7c

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ejrossouw avatar image ejrossouw mikebamber commented ·

"The VE.Bus cluster maintains a single 'global' status for SoC, DC voltage, and DC current. Every DC connection (on every Multi/Quattro and on every battery) has to be connected together to a single DC bus. Do not build systems with separated batteries on multiple (separated) DC bus structures connected to subsets of the Multi/Quattro units in the cluster. This will not work."


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Alexandra avatar image Alexandra ♦ mikebamber commented ·
So there is a load on the inverter - it is the grid. It may not be on the Out put but it still works the inverter.


A short answer- completely independent of each other in operation and not connected to one GX - they don't need to share a bank.

If they are going to share a GX, be in software told they work together then they should share a bank. (Sharing/connected by VE BUS)

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Alexandra avatar image Alexandra ♦ Alexandra ♦ commented ·

https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems#configuration...

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mikebamber avatar image mikebamber Alexandra ♦ commented ·
Many thanks for that. I guess then my question would be - do the batteries in the bank all need to be the same type? They would all be LiFePo4 but different capacities. What would be the workaround for that if there is one?
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