ehsab avatar image

3-phase Quattro + Backup is that possible?


I currently have 3xQuattros operating in 3-phase mode.
Is it possible to add a fourth Quattro, in just inverter mode (utilizing the same battery as the other quattros)?

I would like some form of redundancy in case the 3-phase system has an issue (like overload that switches of all quattros).

This is for equipment that has dual PSUs, like network equipment or servers.

Kind regards

3 phase
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

1 Answer
Alexandra avatar image
Alexandra answered ·


Yes. Also no. It wont work the way you want it to.

If you are wanting redundancy (back up for the back up) it is better to have it a separate system entirely with its own battery.

A battery can also shutdown from an overload (depending on what battery you use of course). SOC can be an issue. If you have it as a slave on one of the phases then it will be affected by the system shutdown anyway.

You could use a Multi (quattro may be unnecessary) just on ups mode for the system or circuit you don't want to shutdown while the main system recovers.

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

I have 380Ah of Lead, not that likely that the battery will shutdown :)
Not interested in buying more batteries, if i can use what i allready have.

There is not much of a price difference between Multiplus-II or the Quattro, and i think i will be better off with similar units if i need to replace one of the three i have in the 3ph system.

So you say i could use a unit by itself in UPS mode, connected to the same battery bank as the others?
Is this documented somewhere?

Why will it not work hooking up an inverter to the batterybank and have it serving a different load then the quttros?

Kind Regards



Current sharing, SOC and a few other things come to mind immediately. Especially if you are trying to run two systems concurrent. Electrical complications otherwise in ac wiring. There are ways around these issues with planning.

To clarify when I said in ups mode I did also mean on its own bank.

You would not be able to use the one venus to monitor the two systems.

Could you please try and explain why it will not work connecting an inverter to the same DC batteries that the 3-ph quattros are connecting to?
I mean that's just another DC-load, and SOC is handled by my Lynx shunt.
Just like the VenusGX is a DC-load.

Knowing more about your system is helpful so SOC technically will not be an issue, or battery shutdown.

Are you wanting to install it in on one particular phase only?

If it tries to charge pulling power through the one phase you can overload the phase and cause the issue you are trying to avoid.

With the venus only one ve bus system can be monitored and since you want this one separate not affected by the rest of the system it is best not to have them together that way.

If i just hook an inverter up to the DC side, creating a single 230V Leg out of that inverter.
Wouldn't the load be shared from all three fases? since they will help charge the DC bus? (When the grid is connected)
And in the event of a grid powerloss the three quattros and the single inverter will all use the battery for each loads.

I might not be the best explainer, perhaps i should draw what i mean instead?

Kind Regards

I do see what you are saying, if the fourth one has no AC input then there is no load on the main system or the incoming grid in that regard. Then battery overcharging will also not be an issue.

You are basically trying to create a fourth "phase"or circuit from the output.

SOC not being fed to this Victron can be an issue as it cannot share that information from the other system.

This is not a supported documented setup. It can be done but it will not work how you want it to. And has potential to create more problems that it solves. You really need a Tech on the ground as now you are moving out of the Victron Community area of help..

If it really is reliability you are looking for then having a complete separate system with its own battery is better as it feeds the critical system you are trying to protect if or when the main system goes down. And a full bypass switch on the main.

I should perhaps mention that i use the 3-ph quattros as a UPS with Solar.So all current from the grid is flowing through the Quattros, use them in UPS mode atm.

BUT, if they (or any unit) fail, i will lose all power.

Thats why i want some redundancy, and i whant it to be conected to my Venus (well, to the VRM portal any way).


What you should have in your system is a full bypass switch in the event that there is an unrecoverable problem where the system is unable to be restarted without technical assistance on site.