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The spec sheet lists parallel and 3-phase operation for that model. Just remember parallel systems are complex and you really need to know what you're doing, or disappointment may follow.

A 5kVA multi would be a lot easier and more efficient.

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

It is possible to have them the two units in parallel provided their firmware is also the same. Also would suggest you go through this link https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems as well the PDF document 'Wiring Unlimited'. When paralleling systems there also some electrical cabling in terms of thickness, length, etc. to consider. As @nickdb suggested, depending on your situation (budget as well), it would be less complicated, from an installation point of view , to install one large unit as opposed to paralleling smaller units.

Look at the cost/practicality of going to 24 or better, 48V for the batteries. Simple rewire would achieve this. Much better for the load you have, and it's bound to increase in future.

I have installed a few Multiplus inverters in parallel set ups and it is easier to get the interface cables that go between the laptop and the VE bus in the inverter, than trying to do it via the dip switches. First thing is to update both inverters to the latest operating version so there is no confusion between the inverters, but it is not necessary to update the version every time a new one comes available, only do it if the new version will give you some improvement you will benefit from having .... and naturally, update both inverters.

You need to set up one inverter as the master, the other as the slave. When you have them linked correctly. both inverters will be shown in the program so you can choose which you want to be the master and which one the slave.

Halve the shore power input current because now each inverter will see this amount of current as it's maximum available and charge to this limit .... to limit the input shore current to 10 amps, then set the input current to 5 amps and each inverter will only draw 5 amps from the shore power for a total of a 10 amp load on the shore power circuit.

Seriously undersize the cable conductor size for both the shore power in and the inverter output and run these cable as long as you can fit them in your system .... the idea is to force the inverters to share the load and cable resistance works well to achieve this result.

Be sure the linking RJ45 cable is not tight between the units, any strain will result in either one of the plugs making a good continuous contact, or a wire pulling out of the plug contact, from experience, this will send you running in circles trying to figure out just what is going on ....

As far as the battery cables, the first one to the mega fuse needs to be crazy big, 95mm sq seems to work well and don't forget the negative to the shunt needs to be the same crazy big. From the shunt to the inverter, as long as the run is less than a mtr (3 ft) 0 gauge (50mm sq) cable of equal lengths will work fine, the same from the mega fuse to each inverter, but just the negative cables need to be the same length as do the positive cables, not all 4 cables the same length ... hope that makes sense.

Set the warning and shut down battery voltage as low as you feel safe, on our lithium battery set ups we drop the warning voltage to 11v rather than 11.8v and the shut down to 10v rather than 11v. This is because the inverter senses the battery voltage at the input terminals, not from the BMV, so the battery voltage may read fine but the inverters start to flash and alarm or eeven shut down well before the battery voltage is really that low.

The reset voltage still needs to be high enough to avoid the load suddenly dropping the sensed voltage and shutting down again resulting in an on/off/on/off issue and damaging electrical gear and possibly the inverters themselves.

As far as the Multiplus 2 units in parallel, still a work in progress ...

T1 Terry

Yes, you can wire two Multiplus II 12/3000/120 in parallel to get 6000w of inverter. However, you would need to make sure that the wiring is done correctly and that the settings are adjusted accordingly to prevent any issues. Another option would be to consider the 12V/5000W Quattro as you mentioned.

Hi All, there is an update on this from Victron in regards to parallel connecting the MultiPlus II (8, 10 opr 15KvA). You need to install an AC transfer switch to lift the paralell restriction.

Link to the docu: https://www.victronenergy.com/upload/documents/MultiPlus-II_External_Transfer_Switch_application/179843-MultiPlus-II_external_transfer_switch_application-pdf-en.pdf

All said Recap

2 multies give redundancy but need same firmware same length and diameter of cables DC side needs following the docs to the point.

1 5000 on 12V need a serious cabling DC side 4000w plus loss 10% = 360A !!

1 5000 /48 (reconnect batteries to 48V) just about 90Amp (existing cabling?)

Multi/Quatro is in VA so 5000VA aprox. 4000w (PF 0.8) max prolonged needs a well ventilated space