Can I extend existing small ESS with a new 'Inverter RS'?

DIY
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1

Good evening,

I have a small ESS running (Multiplus2 3000 GX + MPPT + EM24 + LiFePO (DIY with JK BMS, connected by CAN to MP2 GX)) similar to this:

myEss
myEss917×502 51.9 KB

Question: Can I connect an ‘Inverter RS’ to this setup to feed an island load?

If yes, can I connect the Inverter RS to the MP2 GX via CAN?

I was searching the forums but no finding. Could you pls give me an advice?

Thanks a lot!

2

Why not using the “Critical Loads” path?

3

Thank you,

This is what I tried but did not consider correctly: The power will be still drawn from the grid.
I want to avoid that the battery is fully loaded starting at noon until evening. To do so I thought to add a load to the battery → RS inverter to feed island from battery only.

P.S. I am not aware of a setting to tell the multiplus to feed the critical load path from battery only (when grid is available).

4

Maybe I don’t get the point here. Your issue is having to much solar input → Batteries are on 100% at noon → solar input is throttled to current consumption, rest is “wasted”. Solution: Connect more consumers to the system to use the “wasted” solar input. Do I get that right?

5

Thank you, correct. The idea is to add more load to the system.

I cannot / should not use the load which is connected to the grid and would prefer to have an island (which would be invisible to the outside).

6

Our setup is similar albeit without solar:

  1. MP-II 5000 GX i.c.w. two BMV-712s, one as Battery monitor, one as DC System monitor.
  2. A ‘thirteen a dozen’ 3kW continuous HF Inverter to feed most of the household loads as an island.
  3. Only certain irregular/controllable peak loads (EV charging, washing machine for instance) run on the grid connected segment. Usually as self-consume unless the load happens to coincide with a low price window.
  4. Instead of solar, a large ‘repurposed telecom’ 8kW HF charger.
  5. A 48V battery large enough to cover several days of low energy consuming household loads.

Works well with DESS and dynamic pricing, buying energy at max mains capacity (230Vac 35A) only during bottom price hours, partially selling back when profitable (enough).

Having all but a few loads in island mode limits the visibility of usage patterns towards the electricity supplier to clean buy/sell loads which is, admittedly somewhat irrational, satisfactory in times of overarching data collection. But with little drawbacks and a marginally profitable DESS a great solution anyways.

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7

So the build-in solution “Critical Loads” is not an option - this will use grid sources if there is not enough battery left. Easy way is to connect a non managed inverter to the battery, connect your loads to the inverter and tell the GX System that it “Has a DC system”. Power Consumption is displayed in VRM. Depending on the interpretation of “island” the grid provider will not accept that.

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8

Thanks @Fruchtzwerg @UpCycleElectric Think I understood. Will try it out :slight_smile: