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Connecting Multiplus and Phoenix VE Direct inverters together?

The question of whether a MultiPlusand Phoenix VE.Direct can be connected to a Venus GX has been discussed and answered. So my question deals with exactly how to connect the AC side. What I would _like_ to have happen is for the Phoenix VE.Direct to power small loads while the MultiPlus24/3000/70 has it's inverter disabled via the Venus. Then when I need a large load, such as a microwave/AC, enable the MultiPlus. To that end:

1) should the two generator AC outputs be connected in parallel, or

2) Should the Phoenix VE Direct 24/500 AC output be connected to the MultiPlus AC1 Input? Would the Phoenix AC then "flow through" the MultiPlus

Background: I have an RV system which is mounted completely external to the RV. I use a 24V 200AH LiFePo4 battery, MultiPlus 24/3000, dual SmartSolar 100/30 and a Venus GX. Shore power comes into the system through a dedicated 30A connector to the MultiPlus AC1 input, then the AC output goes to a hardwired dualphase 50A connector. So I use a 30A cable from shore to the Power Box, then a 50A back into the RV. No holes, no modifications to the RV. If I have 50A available, I'll bypass my power box and just run 50A split phase into the RV directly.

When I'm completely on battery power, I have two use cases for the 110V: A) High power typically running the microwave at 1600W. The MultiPlus and battery handle that without batting an eye. Works fabulously. B) Low power -- maybe 20-50W. Essentially, i'm charging a computer, running a small LCD television, mood lighting on the built-in electric fireplace (no heat -- that's 800W/1100W).

I'm 99% B (low power), 1% A (high power). The problem is that the MultiPlus self consumption and power inefficiencies generating 50W of power mean I'm using 100W-120W 24/7 and I would like to avoid that. At the same time, while I'm an EE and can handle a MacGuyver'ed system, my wife cannot.

Ideally, I'd like to have both inverters on, have the Phoenix on 24/7, generating enough power for the Multiplus to detect it, then have the Multiplus boost when it sees the Phoenix power lagging (i.e overpowered)

Ideas and suggestions are very welcome.

Multiplus-IIVenus GX - VGXPhoenix Inverterinverter current draw
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Thanks Ripper --

Let this be a lesson in doing the actual math instead of just looking at the percentages. Just saved me about $300 and a real headache of connections

2 Answers
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ripper answered ·

As the efficiency of the small one drops of badly, you are likely to blow everything you might save twice and thrice when coming over the threshold as it happens when you charge the computer, watch TV, run the lights and have what ever else on if somebody who doesnt actually cares interferes at the same time.

Running both inverters continous is pretty much the worst case. I know, because I tried ;)

Your 120 W are way off for 50W produced by the way.

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ripper answered ·

I was thinking the exact same thing so I checked. Mine is running 230V though. I just assume it is likely the same when it comes to inefficiencies at 110V. The difference is miniscule in idle and when the small inverter gets loaded past a half of its rating it starts to get bad. So what I want to say is, as long as it is loaded to some extend it doesnt really matter, they are pretty much even until the point where the bigger is better.

I now have the little one as redundancy or for those days when I have to switch off the wifi to save energy. So much more convinient to have the biggin at the ready at all times too, wife will love that


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