mfortinberry avatar image

Using large inverters to power all 220V needs, even when on shore power

Several questions here -

Traditionally with available generator or shore power, charger/inverters are essentially passthrough devices. I am considering an approach where the inverters would always power the 220V AC side of the boat.

My primary need here to to isolate the boat's 220V 50hz system from 60hz power supply. Boat will be 35% of the time in the US and 65% in Europe, so it is being built using 220V/50hz.

However, while it is plugged into a location with 60hz shore power, I would still like it to be able to use all its big 50hz AC powered stuff (AirCon, W&D, water heater, microwave).

What are the considerations/challenges to using two large inverters (8000kVA x 2) to power all 220V on this large power hungry boat?

I will have a large AGM battery bank, over 1000ah and could expand that if needed.

My original idea here was to install a large charger off the shore power into the 48v battery bank. Then running the large inverters to the boat's AC panel.

Will the batteries charge as fast as those AC items can deplete them?

What heat issues will I have on this inverter running all the time?

Should I used a single larger inverter or multiple smaller ones in parallel?

How will this approach impact battery life/inverter life?

How much inefficiency will this introduce, as all AC power is created by inverter?

Should I use the same charger for the generators, or is there any reason to use a different charger?

Will a Victron charger allow me to have two different shore power inputs? One would be a 50a/230V/60hz plug and one would be regular 220V/50hz plug. Never used at the same time of course.

When not plugged in, the generators (2x 9kVA) and solar (2.25kW) feed the batteries. It is only when plugged into 60hz shore power that I have an issue.

Phoenix InverterAGM Batteryskylla tg
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2 Answers
ben avatar image
ben answered ·

I have a slightly similar system, although my fundamental issue is making a system that can accept 120V and 240V on the "input" and always produce 240V on the "output."

I have a single 15KVA Quattro that handles the full house output load, and it also provides charging and traditional pass-through when I am fortunate enough to have a 240V shore supply.

When I only have a 120V supply, I use a separate (smaller) Quattro as basically just a charger, and then the house is powered off the battery via the big one mentioned above.


1. Everything is Victron, with configuration parameters and wiring that I understand well and that I can trust will work correctly across two different units.

2. The big Quattro is oversized for our needs. Do not underestimate how much thermal throttling there can be, especially on charging. I rarely can achieve the rated 200A of charging on my 52V battery pack, and it's almost always because the charger warms up.


1. You cannot view and manage two independent Quattros with one Venus device. (Caveat: there is a very limited way that you can view some parameters of a second Quattro on a single Venus setup, but it is not a normal setup and is text-only.) I ended up with dual Venus GXes, and two separate URLs/panels/VRM sites, to manage the system.

2. Rather like the limited, smaller Skylla units, the 120V Quattros are quite a bit smaller. You need to do the math on your average loads versus your pack size versus a smaller charger, if you go that route.

3. Discharging and recharging does cycle the pack, which to some degree affects lifetime. Opinions are mixed and data is scant on what this really means for different chemistries, but it is a consideration.

4. There are losses in the chain, probably more than you would have with a dedicated frequency-converting device. That may not matter much depending on your use case.

5. To your point about heat, the Quattros in pass-through don't get very warm. They can do get warm when they are doing actual work. This may not be a big deal, depending on where you'll be and how you'll cool the area. Consider the earlier point about oversizing.

If I were doing it again, with a lithium iron battery pack, I would probably stick with the one big Quattro for the inverter side and source a third-party charger for the alternative shore supply scenario. I would do that because lithium charging is dead simple, there is already a BMS that has the charge/discharge authority anyway, and either way I don't have a completely integrated solution because of the Venus limitations (today).

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Great information!

Do you have solar or generator powering your bank as well? I will have both and not sure yet how they will all integrate.

Feel like I am getting closer to the right design though

Yes, both solar and generator.

Thanks Ben - very helpful!

WKirby avatar image
WKirby answered ·

On a 48V system you are pretty much limited to the Skylla-TG 48/50 which will offer a nominal 2.4KW of charge power. You did not say exactly what your nominal power consumption is? You did mention 2x8KVA inverters. So 16KVA as a maximum but surely this is not continuous? I'll assume 8KVA average load? Unless you stack several Skylla-TG chargers together then you are not going to cover your loads. I don't think the Skylla-TG is for you.
You'd actually be better off with a 15KVA Quattro for your shore charging needs. This unit can charge at a nominal 9.6KW, with a wide input frequency of 45-64Hz. This would cover your (in my assumption) nominal loads with charge power to spare. However you might want two of these to accept full power charge from each of your (unsynchronized?) generators. Have some switch gear installed to choose between shore power and generator power.

On the inverter side of things, it's down to cost. Again, you'd be better off with 1x 15KVA Quattro. If you really need 16KVA then you are still better off with 2x 8KVA Quattros. The largest of the "inverter only" range is 5KVA so you'd have to parallel four of these devices which is break even with 2x 10KVA Quattro's.

The long and short of it is that you are pretty much stuck with Quattro's for sole Charger / Inverter roles. Get all of the same model to provide redundancy in your system!

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This helps a lot - thanks! Can I assume here that the Quattro can be configured to work as a stand alone charger or as a stand alone inverter? In my install, one would be the charger and the second would operate as the inverter.

Yes, you can set up Quattro just to charge or invert. You're buying more capability than you need in this case, of course.