Two separate ESS 15kVA and 500VA

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apple047 asked Sep 26, '22

Two separate ESS 15kVA and 500VA

Hi,

I currently have 3x MP ii in parallel, running well in ESS configuration no issues and very happy I chose Victron except after a year I realised the efficiency is not as expected and trying to improve.

I’ve seen multiple posts and read manuals but can’t satisfy my knowledge on what would be the best approach to this particular scenario.

For low demand times I want to implement a small 500VA multiplus and turn off the bigger inverters, connected to the same 40kWh battery

One approach I know would work would be to double all components: Modbus meter, smart shunt, GX device, this wouldn’t be worth the effort

What I’m hoping is to be able to tap in the Cerbo somehow to share the existing data available for the small inverter to keep the ESS grid set point at 0W.

I’ll have to use only the AC IN terminals on both inverter systems for this set up

It’s almost like I would need a transfer switch on the VE bus.

Any suggestions much appreciated

Thanks George

ESS modifications

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Modifications Space

Node Red Space

Answer 1 · 2022-09-27T05:31:02Z

Alexandra answered · Sep 27, 2022 at 05:31 AM

@Apple047

You will need a separate GX if you want the 500VA to use ESS assistant. There is another way though.

Your other option is to use a shunt off the main system, set has DC loads in the main GX and run your smaller loads like that.

That way SOC will remain correct (unless you have smart batteries maybe the shunt is unnecessary)?

With 500VA really as ESS is not worth is if you already have a big system. I mean value vs return on investment (as you already worked out). Mppts will still work to compensate for loads as well.

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apple047 commented · Sep 27, 2022 at 04:28 PM

Running the small loads from the small inverter is not an option as it’s the whole house with many circuits, ideally I would use the small inverters input rather than the output, in case of a higher load security of supply is guaranteed this way.

I’ve been contemplating all day on this challenge, I think I have a solution:

Raspberry Pi running VenusOS, configure ESS assistant and use the 500VA internal meter as grid connection set point, so I can adjust its power output, than I can pull via Modbus house consumption from main energy meter via Cerbo invert the reading and send it to the small system to compensate the house consumption,

I’ll be running one system at a time.

I’ll definitely need some help with the script,

Would it be possible to somehow join the node red signals into one platform?

Thanks

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Answer 2 · 2022-09-27T05:37:05Z

nickdb answered · Sep 27, 2022 at 05:37 AM

Or just buy a 15kVA multi and sell the 3 smaller units.

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apple047 commented · Sep 27, 2022 at 03:53 PM

Good though, I wish this option was available a year ago

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