Multiplus II GX ESS System Design

DIY
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Hey there,

I have a design question that I am hoping to get validated if possible!

I’m currently working my way through the Victron online training, reading manuals and scouring forums for similar setups. I think I’ve learned enough to hopefully come up with a valid design.

I have a pretty complex on-grid setup here (UK based) that’s evolved over the years, all installed by myself and my electrician.

Briefly it comprises 3-phase grid supply but operating as 3 separate single-phase systems:

  • L1 - house loads consumer unit - Solaredge 3kW PV string inverter & 3.33kW panels, Sofar Solar 3kW ESS AC coupled with 16.1kWh Fogstar battery
  • L2 - garden office loads consumer unit - Sofar Solar 3.6kW PV string inverter & 4.25kW panels, Sofar Solar 3kW ESS AC coupled with 16.1kWh Fogstar battery
  • L3 - garage / workshop loads consumer unit - 3 x 1kW Solax micro PV string inverters & 2.7kW panels

This all works well as 3 isolated single phase systems and I am well versed in setting up, configuring and managing all these different manufacturer systems.

I now want to add ESS AC coupled to L3 phase to support the garage / workshop loads, using another 16.1kWh Fogstar battery.

I was initially planning on sticking with what I know and adding another Sofar Solar inverter as I’ve found them to be easy to configure and pretty reliable. Being AC coupled they pretty much “just work” out-of-the-box. Unfortunately, Sofar Solar pulled out of the UK a while ago, so new equipment is hard to find.

Therefore, I think it might be time to learn something new for this current project, hence I’ve started looking at Victron.

I’d like to keep things simple and with as low an entry cost as possible, otherwise the project becomes less attractive. In the future I might well move to a full 3-phase Victron parallel setup, however at the current time it doesn’t make sense to remove existing equipment that is fully functioning or to add lots of separate individual Victron components.

The Victron setup needs to replicate for L3 what the current Sofar Solar 3kW ESS give me on their respective L1 and L2:

  1. Simple AC coupled ESS - doesn’t need UPS or anything fancy, just needs to discharge the Fogstar battery to support loads connected on the grid side

  2. Needs to detect and use any export on the grid side when available (from the Solax micro PV string inverters) to charge the battery

  3. Be able to set charging from grid side on a schedule (e.g. overnight on an off-peak tariff)

From my research so far (along with some pointers from a local supplier) I think I’ve come up with the following:

  • Multiplus II GX 5000 (70A limit from battery so will give similar output capacity to the current Sofar Solar ESS)
  • Victron Current Transformer 100A:50mA
  • Victron Can-bus BMS Cable Type B

Are the above components enough to get me going?

In terms of setup and configuration via VRM, is this likely to be pretty simple?

I believe that it should work, albeit the VRM display may not show full data as it will only see the grid reading positive / negative and won’t have info for the PV (from the Solax micro PV string inverters) nor for the loads (from the garage / workshop consumer unit).

Thanks for reading!