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valden asked

MultiPlus 12/3000/120. Do I need 16 or 50 Amp version?

I searched but answers not found. Please help with this MultiPlus question.

I'm about to order a full suite of Victron devices for a lithium battery and solar system on a yacht. Storage will be at 12V, with four 12.8V 300Ah Smart lithium batteries - so 1200Ah. A Multiplus 12/3000/120 will provide charging from 230V AC shore power, as well as on-board inverting when needed. This Multiplus is available with either 16 or 50 amp Transfer Switch.

The MultiPlus' maximum charging output of 120A is ideal for the planned battery bank, being 10% of the Ah rating. Question is, should I choose the 16 or 50 amp version? Is the 50 amp version only intended for yachts typically used in 115V shore power regions? Or is this 50 amp version a good choice for my yacht, given the capacity of the battery bank? It could be that the 16 amp version will not be able to supply house AC (say, an electric fan heater) and charge the batteries at full rate, simultaneously.

Am I understanding this parameter correctly? Thank you.


MultiPlus Quattro Inverter ChargerLithium Batteryyacht
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jwfrary avatar image jwfrary commented ·

“say, an electric fan heater) and charge the batteries at full rate, simultaneously.”


multi plus will use approx 6-7 amps of power when charging at full power. So on a 16 amp supply, you will already struggling to run a fan heater at the same time without impacting on the battery charging rate which the multi will do automatically.

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jwfrary answered ·

Hi

Simply it refers to the rating of the contacter in the unit.

So if your using a 16amp shorepower inlet then the 16 amp one is fine, if your using a bigger input like 32 which is getting more common in marinas, or you wish to expand your system in the future then might be best to go bigger.

I would say, go with a bigger contactor, and fit both 32amp shore inlet. You can always control the amperage down to 16 by means of a simple converter and a Gx device or the multi panel.

benefit being you can use more shore-power before you start compromising on battery charge rate.

If you have a generator onboard, or plan to in the future you should punt for the Quattro.

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valden avatar image valden commented ·

Thanks J. Your reply makes sense to me.

Question - does being able to use a 32 amp supply depend on the kind of shore power inlet installed on the yacht? I think I'll need to check on what my yacht builder will be installing. Perhaps I can influence this.

If I understand correctly, it seems there would be no point in requesting a 50 amp MultiPlus if the shore power inlet is limited to 16 amp (if that's how it works). Though, I imagine upping the shore power inlet later on would be possible, to take advantage of a higher spec MultiPlus.

Re the Quattro, yes, I've been looking at that. I won't have a generator installed during build and don't plan to retrofit one. Instead, I'd get an Integrel On-Engine Generator (a really big 48V alternator). This would require a 48V Quattro. I'll worry about that later.

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jwfrary answered ·

Cost between the 32amp input and a 16amp cable /connection is pretty similar so spec at this point as to preference/what is fitted where you will be cruising and taking into account what your onboard consumers will be. If you have electric cooking/ac or heating you’ll want the 32amp.

If your thinking about an integral, then you would be better to configure your system to suit now as the cost to change it in the future will be significant.

I suspect if you compare the benefit to the cost you will likely fit a second alternator at 12v like a balmar or a master volt which offer 150-200amp options, for significantly less money than the integral, which is a great product neatly packaged but it’s pricy and would involve changing nearly all of what your putting in now of top. Wouldn’t doubt the price difference being 5 digits.

What’s your main engine?

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valden avatar image
valden answered ·

Hello again. After asking the original question and enjoying the replies (thank you) I found that I was still not entirely clear on how the 16A vs 50A versions of the MultiPlus 12/3000/120 differed. I believe I've discovered why I was struggling with this. It's the Manual! It's very confusing, if not downright misleading. Or just plain wrong. Let me show you. First, a link to the document

MultiPlus manual

Here is the second paragraph of section 2.1 on Page 2. This text describes how a MultiPlus can perform as an uninterruptible power supply (correct) and implies (or directly states) in the last sentence that the two variants can take over either 16A or 50A of current (not correct). The problem arises from the use of the words 'switching', 'switched' and 'switch' in the heading and through the paragraph (correctly) and then again in the last sentence (incorrectly). Have a look. :-)

Automatic and uninterruptible switching

In the event of a supply failure or when the generating set is switched off, the MultiPlus will switch over to inverter operation and take over the supply of the connected devices. This is done so quickly that operation of computers and other electronic devices is not disturbed (Uninterruptible Power Supply or UPS functionality). This makes the MultiPlus highly suitable as an emergency power system in industrial and telecommunication applications. The maximum alternating current that can be switched is 16A or 50A, depending on model.

Elsewhere in the manual the word 'transfer' is used in describing the difference between the versions and what is actually happening. See paras 4.3.1 and 4.3.2 on page 9. This is much better. Here, we read how the 16A or 50A specification refers to how much current from shore power or a generator the MultiPlus can pass through. Or 'transfer'.

4.3.2 Models with 50A transfer capacity (eg MultiPlus 12/3000/120-50 230V)

With its PowerAssist feature the Multi can add up to 3kVA (that is 3000 / 230 = 13A) to the output during periods of peak power requirement. Together with a maximum input current of 50A this means that the output can supply up to 50 + 13 = 63A.

Hmmm. These paragraphs might have been written by different people at different times; quite likely given the iterative development of such products and documentation. :-)

The word 'transfer' is used in the heading of paras 4.3.1 and 4.3.2. It's a word that describes passing or moving something from one place to another. On the other hand, the word 'switch' means changing the source or destination of something.

A MultiPlus 12/3000/120-50 can transfer up to 50 amps of current from a shore (or generator) input, for use by the AC circuit, including by itself for charging batteries.

A MultiPlus 12/3000/120-50 can switch its source for up to 13 amps of current from a shore (or generator) input to its battery/inverter input.

A MultiPlus 12/3000/120-50 can add up to 13 amps of current sourced from its battery/inverter input to up to 50 amps of current sourced from a shore (or generator) input, to make up to 63 amps of current available to the AC circuit.

The 16 and 50 amp specifications for the two MultiPlus variants should only be discussed in terms of transfer capacity. These specifications shouldn't be discussed in terms of the uninterruptible power supply function.

*****

What's the best way to flag for review the second paragraph of section 2.1, Page 2 of the MultiPlus Manual 12/3000, 24/3000, 48/3000?

@Jwfrary @Daniël Boekel (Victron Energy Staff)

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JohnC avatar image JohnC ♦ commented ·

@Valden

In the Multi sense 'transfer' means more than just switching ac sources. It also means 'switching' an earth-neutral link (which you can turn off if you choose).

In the Multi spec sheets it's listed as 'Transfer switch (A)', and in the Multi II's, 'Maximum ac input current'. I see both as being correct, one perhaps aimed more at casual browsers than the technically inclined/installer.

In a ups situation with a power failure, the transfer relay will switch both the MEN link and AC2-OUT.

Call it what you will..

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valden avatar image valden JohnC ♦ commented ·

Helpful info John. Thanks very much.

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jwfrary avatar image
jwfrary answered ·

@Valden

The words switch and transfer are really being used interchangeably. - I just depends on the way in which its being used in the sentence.

fundamentally the answer lies in the wiring schematic

Simply the rating for the contactor that attaches the supply to the unit is rated at either 16 or 50amps dependent on model.

The Second AC2 contactor is rated always to 16amp.

Thus the thrust of the meaning of the documentation is that the wiring on the output side of the inverter, needs to be able to handle the additonal current.

When we think about the availiblity of breakers - 63 amp breakers are pretty easy to come by off the shelf so this makes a lot of sense.

If we think about smallish marine generators, say 7 kw would have a typical output of around 23amps so even fairly modest sets are going to be overloading your 16amp version. Hence most boats fitted with AC gennerators go for the 50 amp version - Indeed a quattro is a better idea here anyway.

If you dont have a generator or you have a DC generator(Alternators or dedicated) and will only use a 16amp shore supply, then the 16amp version is a good choice.

Hope that helps.

Bear in mind that the documentation is written for distrubuters and electricians not your average owner skipper.



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valden avatar image valden commented ·

Thanks for this reply J. The 50 amp version is the right one for our yacht.

We won't have a generator, so don't need a Quatrro. If/when we install an Integrel On-Engine Generator (as they like to call their fancy, expensive but very good alternator), it'll need a 48V Quattro. We'll cross that bridge later. A Balmar 220A 12V alternator might be the more palatable solution ...

I'm still calling that second paragraph in Section 2.1 of the MultiPlus manual a howler! :-)

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