Adding a second inverter/charger (115V) to our existing REC Q setup (with a 220V inverter/charger)?

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dahlke asked Jan 11, '24

Adding a second inverter/charger (115V) to our existing REC Q setup (with a 220V inverter/charger)?

Ahoy :)

Question: is there a good way to add a second inverter/charger (115V) to our existing REC Q setup (with a 220V inverter/charger)?

We have REC Q BMS, 220V/24V Victron Energy Quattro, Victron Energy 3600 isolation transformer, and 7 kWh of LiFePO on our boat. We have finally made it across the Atlantic and were planning on using the isolation transformer to step up the voltage (115V -> 230V). Unfortunately, the shore power voltage is too high here. Measured to 129V on the dock. That gives us 280V on the secondary side of the isolation transformer - it looks like the 220V Quattro inverter/charger won’t accept anything above 265V.

Is there a good way to add a 115V Victron Energy Inverter/charger to our existing setup? Is it possible to just connect the second 115V inverter/charger to the Cerbo GX box (like the 220V inverter/charger), or won’t that work? And advice on what to do on a 220V boat in 115V countries?

battery charging BMS multiple inverters Isolation Tranformer

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Alexandra ♦ commented · Jan 11 at 12:12 PM

@Dahlke

System battery voltage would be useful to know.

There are quite a few options out there for the different battery voltages.

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dahlke Alexandra ♦ commented · Jan 11 at 12:18 PM

Oops, 24V :) I'll add that information to the question.

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Answer 1 · 2024-01-14T03:17:10Z

Paul B answered · Jan 14 at 03:17 AM

your issue is the isolation transformer output check that the jumpers are setup correctly on the input voltage detection. Also what model isolation transformer is it I am guessing that its the auto version. this should be working I would have thought. you might have to increase the aceptable input range of the quattro

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dahlke commented · Jan 16 at 11:33 AM

Hi Paul,

Thanks for your suggestions :) We have the “none auto” version, but I’m 100% sure the configuration (115 to 240) is correct.

Am I correct in thinking that whatever voltage the Quattro accepts, it will sync to (just like with frequency)? Meaning we would end up with 280V on the boat. What kind of range do typical household appliances and electronics support? 280V just seems high :)

I tried contacting REC BMS to get their opinion. Sent them basically the same text I posted here. They replied with one very short sentence: “Yes just use a second inverter 120V”. A somewhat frustrating answer as it took them five days to come up with and also won’t let us charge off of shore power (which was the whole point). I’m a little hesitant to contact them with further support inquiries ;)

I did the installation of the REC BMS myself, and I have a spare one aboard the boat. I guess I could use that to make a test setup and emulate a bad cell and over/undercharge. That way, I could verify that the BMS trips the contractor in those conditions - I expect it will. Then I could just setup the 120V inverter/charger to be well within my current settings in the BMS. Does that sound like a decent idea?

We have 1600W of solar and a high-output alternator (controlled by the BMS) that should do a fine job of getting us the last bit of the way to make sure the BMS balances the cells with the conservative settings in the 120V inverter/charger.

The reason for wanting a second inverter/charger over just a charger is that we’ll be running air conditioning off of the 230V inverter/charger in marinas, so the charger needs to be a decent size, and it would be nice to be able to buy a new toaster if our 230V version breaks no matter what country we’re in - the toaster is just an example :)

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Answer 2 · 2024-01-14T03:21:55Z

Paul B answered · Jan 14 at 03:21 AM

Another way to go is buy a large 115v 24 volt battery charger and charge the batteries only with it and then use the quattro as if you have no shore power.

note be carefull here as the batteries bms will need to be able to isolate the charger if there is a cell overcharge issue. this may involve a extra relay being installed so contact the person who installed the rec bms and discuss this.

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Paul B commented · Jan 14 at 03:35 AM

If you need assistance then I can help remotely as long as the cerbo is connected to the Victron VRM via the internet. if you are having support issues. whats app me if needed +61484300253

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