Quattros in series to reduce quiescent current

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bkarr asked Aug 28, '19

Quattros in series to reduce quiescent current

I'm upgrading my boat house bank and inverters to supply new heavy loads like induction cooktop, demand water heaters, and A/C. I'm trying to figure out what quattro setup will minimize the quiescent drain. The system is 24v 1300ah LiFePO battery bank, and either two Quattro 24/8000, or 2-3 Quattro 24/5000. I've heard the quiescent drain is rather high on Quattro, especially the 8k version. I would like to avoid high parasitic drains on the system.

If running two Quattro in parallel is the full active Iq going to be drawn by both? or does one step in when the other is heavily loaded?

If I run one Quattro into the second Quattro with the second configured for PowerAssist will that reduce the Iq on the second quattro? What is the Iq of the Quattro when in Powerassist mode, but not supplying current?

Are there any issues with daisy chaining Quattros like this?

Any suggestions on Quattro selection and/or topologies to address my needs would be appreciated.

inverter current draw powerassist

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Answer 1 · 2019-08-29T01:55:05Z

ceriw answered · Aug 29, 2019 at 01:55 AM

When running in parallel, the units load share equally. I've got 2 8k 48v units set in parallel and the no load consumption varies from about 80W to 130W. In power assist or UPS mode, the consumption is higher, even with no load. I think most of the power is lost in magnitising flux of the large transformers in these units.

I haven't tried series connecting them, but the 1st issue I can think of is your CCGX is only going to be able to connect to one of the units. This means that you are either not going to be able to adjust the shore current limit on the 1st unit or you are not going to be able to see your power usage on the second one. You would also likely need a separate BMS as you won't be able to track DC current on both devices.

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bkarr commented · Aug 29, 2019 at 10:55 PM

Thanks for the response. is that 80-130W for each unit, or both together?

I was thinking of hooking both units to the same battery with a single BMS (third party, LiFePO batterys are not Victron) and a Victron BMV-712 smart.

I have an Octo GX for interface and a bunch of 100/15 MPPTs, not a CCGX. Does the Venus system allow only one Charger/inverter connection?

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Answer 2 · 2019-11-19T21:42:52Z

d-clark answered · Nov 19, 2019 at 09:42 PM

@bkarr, I am interested in exactly the scenario you describe. Did you find a configuration that works where one of the Quattro units is only used to invert when required? I saw a youtube blog on a large electric propulsion catamaran was configured as he described as one of the Quattros acting as shore power into the other and the second supplying the power assist only when demand dictates. He states specifically that this was done to minimize quiescent drain.

https://www.youtube.com/watch?v=nchKhM_TxYk At the 9minute mark.

I would like both Quattros to charge when the generator is running and only one to invert except when the demand warrants which will be seldom. I currently have one unit and had an additional charger that came on when the generator ran. It died and I would like to replace with duplicate of existing quattro. that would give me redundancy as we sail to remote locations. And it would cut the generator time, And set me up for higher draw items running concurrently. I just need to understand the options for connecting these before I proceed.

Unless there are considerations beyond monitoring with CCGX or BMV-712. I would think this would be a configuration that would benefit many users.

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