Paul Simon avatar image
Paul Simon asked

3-phase Quattro setup, single phase grid charging.

Hello, I am currently in the general planning phase for the build of my future liveabord sailing catamaran. I want to install a diesel-electric propulsion system with two electric motors (one in each hull), large LFP battery banks (57.3kWh in total), lots of solar panels with several Victron MPPT chargers and a 16.4KVA 3-phase diesel generator for charging the batteries when there's not enough sun.

For charging the batteries from the generator I wanted to use three Quattros in a typical 3-phase setup. In my home port I will have access to a 400V 3-phase land connection to charge from the grid. But in other ports there's usually just a single 230V phase available.

  • Will the system still be able to charge the batteries from a single phase grid connection in that case? So for a setup of three Quattro II 48/5000/70-50 I will still get 70 Amps of charging current instead of 210 Amps with a 3-phase land connection? Or will the system stop charging completely?
  • Will I have to run the inverter functionality of all three units all the time with corresponding zero-load power draw (3*18W = 54Watts) or can I switch on and off single phases in my boat just as needed? Most of my home appliances will be 230V, but the diving compressor will be 400V. It would be nice to be able to run it from the batteries without having to start the generator when there's a surplus of solar power anyways.

Thanks for your help! Cheers,


3 phaseQuattro-IIyacht
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2 Answers
Alistair Warburton avatar image
Alistair Warburton answered ·

Because of the way a Quatro is built you cant set them up to charge without connecting AC In to AC Out at the same time, that means for a 3 phase system single phase cant work unless the system, as a whole, will allow you to run a single charger on one of the phases/units.

I don't know if that is possible, I suspect it isn't, but it is a more specific question to look for an answer to. Some context may help:-

A Quatro has a single transformer, and bridge, when inverting they delivers power to the outputs, and input if export is enabled, when charging it draws power from the input, or the output with AC coupled Solar, and delivers it to the battery.

In a 3 Phase system three of these are coordinated to operate 120 Deg apart so you cant have the inputs, or the outputs linked, hence my comment on running a single charger in one unit

There is no reason you cant add a single phase charger, that connects to the battery directly, and isn't connected to the 3 phase input of the Quartos, its an additional shore power cable to lug about but standalone chargers are a thing and its a simple solution that also adds redundancy.

Sorry I cant give you a better answer, hope this helps find one.

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Paul Simon avatar image Paul Simon commented ·

Yeah, that is basically what I suspected too. Just wanted to make sure of it with the help of someone who has intricate knowledge of the Quattros. So I guess I will have to install another charger for single phase 230V charging. Unfortunately Victron only offers the Skylla 48/50 TG for 48V systems. That thing is pretty bulky and heavy regarding it provides only 50 Amps of current. The Mastervolt unit with identical performance is bulky as well, but flatter and a bit lighter. Had hoped to be able to skip it...

Thanks for your reply, though!

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Kevin Windrem avatar image
Kevin Windrem answered ·

I believe you can set the 3-phase system up to accept AC input when all three phases are not available. The trick is to turn off "switch as group". This will then allow one Quattro to charge (and pass through power) while the other two run in invert mode. This should also work with two phases available if you ever run into that situation.

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Paul Simon avatar image Paul Simon commented ·
That'd be awesome! Can anybody confirm this? I would really like to get away without having to install another 10kg single phase charger that is only used in rare occasions...

Thanks, Kevin!

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Alexandra avatar image Alexandra ♦ Paul Simon commented ·
@Paul Simon

Confirmed you can do the single phase in with switched as a group off on a three phase system.

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Paul Simon avatar image Paul Simon Alexandra ♦ commented ·
Thanks to both of you, Alistair and Alexandra! That is great news. Construction of the hull will start this winter and will take several months. So it'll take quite some time before I will be able to commission the propulsion and electric systems...
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Alistair Warburton avatar image Alistair Warburton Paul Simon commented ·
Nothing to loose trying it, Victron wouldn't put a system out in the wild that was going to damage itself the first time a phase failed. If you cant get it to work, just make sure you left enough wall space for the charger! (Or a couple of smaller chargers, which would be an option if Plan A turns out to be problematic)
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Alistair Warburton avatar image Alistair Warburton commented ·
It sounds entirely plausible to me electrically, it just seems a little fast and loose for a Victron decision, although I guess that has been changing over the past few years.

You would need to be careful 1 or even 2 phases of a 3 phase supply sounds doable and wouldn't do any harm that I can think of the three units would be tracking individual AC voltages anyway.

Just remember 2 phases of a 3 phase supply is NOT split phase, they would be 180 Deg apart and you absolutely can not connect 1 phase to more than 1 Quatro.

I lake days when I learn something... Please update the thread when you try, or get someone else to try on their setup for you.

One last Caveat, make sure the earthing and protection is still good. In island mode, on the boat you will probably be using TT, IE, Earth and Neutral separated and RCD's protecting all circuits. connecting that to a none TT shore system isn't a huge issue. However if the boat is using ground/hull referenced protection and the ground rely is being used to create a PE-N link when islanded it could do some odd, potentially unsafe stuff, when shore power is connected. you just need to work through the calculations, me I would go TT or even IT.

I will keep an eye on this, good stuff.

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Paul Simon avatar image Paul Simon Alistair Warburton commented ·
Yeah, that would be next on my list... I am leaning towards a TT network arrangement and isolation transformers on all phases (although their weight is a bitter pill to swallow). For safety reasons and to avoid galvanic corrosion.
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