Which MultiPlus to add to existing configuration

DIY
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Hi, I have 2 x MultiPlus 12/3000/120 inverters configured as split-phase running off a 1120 AH lithium house bank. I’ve had this particular config since early 2025 and it is working very very well. I’ve also got a bunch of other Victron gear, but I don’t think they’re relevant to this question.

However, I’d like to add some charging capacity to reduce gen run time. The gen can easily handle another 120A charger, and the batteries can easily accept that. I’ve looked at many different solutions but what I’d like to do is add another MultiPlus and run it just as a charger. I have no need of any additional inverter capacity, and the price difference between a MP and just a big charger is not a showstopper….particularly when you consider the big hidden benefit. And that is to have a whole MP available as a “spare” if one of my existing ones fails. This is not something I would normally plan for except for the excuse now of wanting the additional charging anyway, plus one of the MPs is 10 years old the other about 7, so while not “old” they are not “new” either. Because of the split phase configuration, if I lose one of the MPs I am essentially knackered until I would do some (minor) re-wiring and then reconfigure the remaining MP to be a basic 120V single unit. This would be a major PITA in the middle of the night in the middle of a remote anchorage in the middle of nowhere, which is where this kind of thing happens. With a “spare” MP sitting there, it would be a trivial matter to just plug-n-play drop it into the failed unit’s space. There are some other hidden advantages as well but you get the gist.

My question is - which MP to use? Since my originals, there is now an MultiPlus II, and MultiPlus II 2 x 120V units. They seem to boast additional function and are even less expensive. However what I do not know is whether either of them would seamlessly drop into place to replace an older original MultiPlus. This is a key point because in such a scenario the seamless drop-in is of paramount importance.

Or, should I just stick with the exact same unit, a MultiPlus 12/3000/120?

Thanks

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Be aware of compatibility version if you will ever run them in parallel on same leg. For split phase shouldn’t come into play. Check with dealer for ultimate confirmation that new unit will play nice with older ones.

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  1. Multiplus is more selective about the purity of the AC it accepts then a dedicated charger.
  2. If you want to also be able to use the charging MP2 as a ‘spare’ in case of a unit failure, then you must use exactly the same model as your existing MP’s.
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Thx @Brucey, no parallel, just split phase.

Thx @MikeD, that would settle that then. In essence I was asking if you could run a MultiPlus and a MultiPlus II in a split phase configuration. I believe your answer is no. No worries I’ll proceed with getting another old-school MP. This won’t happen until October when we return from cruising, just wanted to do some advance planning.