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ruburn avatar image
ruburn asked

MultiPlus-II AC-In for Battery charging only?

I’ve been looking at the Victron products with a view to installing my own domestic Solar PV system that can provide 230v AC power for a couple of circuits in my home, without having to go down the “Grid-Tie” option which introduces a number of limitations (Inverter capacity being the main one) from the network operators, etc.


I’ve been looking at the MultiPlus-II and it looks like it might be able to provide the solution I’m looking for, but I have a few questions that I hope you can answer to clarify my understanding:


1) Presumably, the MultiPlus can be used in conjunction with an MPPT charge controller to charge the same battery?

2) Can the AC-In connector on the MultiPlus-II be used just to charge the battery during the night, with no output back into the Grid?


My solution would look similar to the standard one from the manual shown below, but with the Grid only supplying incoming AC power:


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Multiplus-II
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5 Answers
snoobler avatar image
snoobler answered ·

1) Yes.


2) Yes. Using ESS.

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ruburn avatar image
ruburn answered ·

Thanks snoobler, I'll have a look at that link :-)

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ruburn avatar image
ruburn answered ·

I've had a very quick look at the ESS docs you kindly suggested and it "seems" to suggest that I can do what I want (as shown in the updated diagram below) but it also states that it must have a GX device but I'm not sure what this actually achieves in my scenario?


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wkirby avatar image wkirby ♦♦ commented ·
The problem that I can see with ESS is that it is essentially grid tied, it needs a grid code to be entered in to the MultiPlus to tell it what region it is operating in. Even if you set it to "Do not feed in excess energy" the network operator may have a dim view of that since it "is capable" of feeding energy in and is running "grid parallel". Yes, you would also need a GX device for this to tie all the components together.

If all you want is a timed charger, solar charging and you are not interested in any online monitoring then I'd simply wire the MultiPlus' AC-IN via a suitable timer switch. This would simply apply AC to the MultiPlus during the night (or whenever you plan to charge from the grid) and charge the battery. The solar MPPT will act independently too. This way there are not grid codes or network operator authorisations needed.

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ruburn avatar image ruburn wkirby ♦♦ commented ·

Thanks WKIRBY, what you're saying makes sense and seems to mitigate the issues of upsetting the network provider, G98/99, etc. Although, even with a timer on the AC-In it sounds like it still might contravene the UK regulations if there's a chance it can send power back to the Grid?


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wkirby avatar image wkirby ♦♦ ruburn commented ·
If the MultiPlus is not configured with a grid code then it cannot send energy out to the network. It will only consume AC power to charge the battery or pass through to AC-OUT. It would simply act as a appliance in this configuration, which is the standard factory configuration. The DNO should not be concerned with that.
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ruburn avatar image ruburn wkirby ♦♦ commented ·

If that was the case then it answers my question but I guess it's down to the DNO at the end of the day unless we can "prove" that the config is incapable of sending anything to the Grid if it doesn't have the "Grid Code" entered?

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ruburn avatar image
ruburn answered ·

Think I've answered my own question, the GX device is used to monitor the system and is "built-in" to the MultiPlus-II GX :-)


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nickdb avatar image nickdb ♦♦ commented ·
It is no more expensive having an external gx and this option is more extendable.
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kevgermany avatar image kevgermany ♦♦ commented ·
GX also provides central control for the system.
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ruburn avatar image
ruburn answered ·

Here's another idea I had, to use a "charger" as the PV input during the night (on a timer), in order to top up the battery ready to be used in the morning:

1645087751599.png


I guess there might be an issue with having the PVs and Charger connected to the PV terminals of the MPPT, but if the charger is off during the day would that be an issue?


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