Multi RS Solar with Auto transformer

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2020vrb asked Nov 24, '22

Multi RS Solar with Auto transformer

I am thinking through a lithium/solar upgrade with increased inverter power for my RV. I love the design of the Multi RS Solar but need 120v loads for my US based Rv. Seems the autotransformer would work to solve the output, since you can adjust the RS to be 60hz and 240. I assume I would likely need two autotransformers to also enable15/30/50 amp shore power.

Does he Multi RS Solar (48/6000) work with the autotransformer?

https://www.victronenergy.com/upload/documents/Autotransformer/Autotransformer-en.pdf

Multi RS

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Answer 1 · 2022-11-29T21:40:31Z

2020vrb answered · Nov 29, 2022 at 09:40 PM

Bumping this after the holiday weekend.

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Answer 2 · 2022-11-29T22:02:07Z

Kevin Windrem answered · Nov 29, 2022 at 10:02 PM

I see no reason you can't use transformers in and out of the Multi RS Solar but I think there are better alternatives such as a Multi II 2x120 and separate MPPT controller.

The Victron isolation transformer might be a better choice for the input side if you can live with the 3600 watt limit. There is even a model that will automatically switch between 115 and 230 volts on the input and produce a 230 volt output.

Victron autotransformers have a limit of 32 amps of neutral current so that's something to consider. If your shore power is limited to 30 amps for 120 volt single phase and you balance your loads between two legs you should be OK.

The Multi RS Solar is a 48 volt system only so you'd need to take that into consideration. There's no direct conversion from 48 to 12 volt at least from Victron so you'd need to do that it tow steps or find an alternate from another transformer.

The other hurdle is the MPPT controller needs to see a MINIMUM of 120 volts from the PV array to start up.

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shaneyake commented · Nov 29, 2022 at 11:30 PM

On the DC-DC note: Victron does make a DC-DC to go from 48v to 12V, I use them all the time.

https://www.victronenergy.com/dc-dc-converters/orion-tr-dc-dc-converters-isolated

But I would also go with a 48V Mutliplus-II instead of the RS inverter for RV applications.
The MPPT in the RS min voltage is too high for most RV arrays. SmartMPPT will turn on at 5V above battery, so like 60V instead of the 120V.

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Answer 3 · 2022-11-30T06:02:58Z

2020vrb answered · Nov 30, 2022 at 06:02 AM

Thank you Kevin and Shaneyake this is great information.

The system I am contemplating is a Lithionics 51volt battery specifically for the inverter and 12v for the 12v system. I would add enough solar (probably around 3000w) to top up the batteries during the day. I want to be able to run the air conditioners on Inverter only (2 - 15,000BTU roof top systems) and only really use the generator to top up batteries when necessary. I am also aware you can set it up so the Inverter is offsetting shortages in shore power when connected to 15/20 or 30 amp service using the Hybird approach. My coach is a 50amp all electric.

If I understand, I will need a Multi II 2x120, at least one (possibly two) MPPT controllers, a 48/12 dc/dc converter, and the Cerbo GX. One issue here is I only see the Multi II 2x120 for 12 or 24 volt systems, not 48. I assume there are not similar solutions for 48v in 120v systems? Looking at the main Victron site, the Quattro seems to do what the Multi II 2x120 does and has a 48v version with 5000W output.

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shaneyake commented · Dec 22, 2022 at 10:25 PM

The Quattro does not accept 120/240 split phase.

The Multi II 2x120 is only a single 120V inverter, the L2 can pass through the grid or connect L1 and L2 but can only run 120V loads when not connected to the grid.

What you would want is to install a Multiplus-II 48/5000 230V with an autotransformer or

2x Multiplus-II 48/3000 120V and run in split phase config.

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