Off grid + grid charger

Q&A and troubleshooting
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1

Hey all.

Here’s the situation. I have an installation with the following devices:

  • x3 Victron Multiplus II 15kVA in parallel, currently off grid.
  • One Dyness B3 battery bank
  • Lynx Distributor
  • x2 RS MPPTs
  • Cerbo GX

My issue is this:

I have two grid AC inputs that I would like to use to charge the batteries exclusively. The problem is, they are too weak and different for the 3x15kVA inverters so they disconnect or cannot sync at all to the grid.

The apparent solution is to install x2 smaller Multiplus 3kVA, which should connect to these weak grids.

I have concerns regarding the correct communication and if possible, to allow VRM monitoring of how much these two inverters are charging the batteries, not just seeing the DC Voltage.

My provider said it is not possible to have different inverters on the same GX, even if they are different VE-Bus. So the solution he gave me was to install a second Cerbo GX in order to see the two 3kVA inverters, but I will only be able to see the voltage and amperage, no charge flow or SoC, which would be a shame.

I have read it is possible to use different clusters on different VE-Buses. Since I would need three, I would need a mk3-usb adapter and connect a USB from the cerbo to the 2nd 3kVA inverter. (I assume I cannot daisy chain them two because they are different grids?)

If not, I also read that if using two cerbos, I can use the battery VECan with a splitter that goes to both cerbos, therefore achieving SoC data on both. Is this a thing? My provider cant say if it would work.

So, in short

  • Existing 3x15kVa Multiplus II off grid, connected to MPPTs and battery through Cerbo GX, supporting all loads
  • Adding two standalone 3kVa Multiplus II, only to be used for battery charging. No AC OUT.
  • Each new inverter has its own AC IN, with different voltage and all
  • Best case would be to add it to the existing plant. If not, a separate plant with separate Cerbo GX, but SOC and charge flow visibility wanted (to know how many watts its charging)

What would be the best solution?

Thanks in advance

3

Look at the cerbo GX manual und search for MK3

The MP2 “Chargers” musst be connected to a separate MK3

Other possibility is a second Cerbo GX with common Battery CAN.
Other as in your post you must loop battey CAN through both GX devices and connect the terminating resistor to the last device at the end.

I set the version mit secondary MK3 up to test it because I was curious. ESS system and a second MP with own MK3 as a charger

But you wrote that you have two different power sources?

4

@layonduff
Pls consider using power supply units (PSU) for 48V telecommunication services.
Common are Eltek Flatpack 2 and Huawei. You can get used ones at eBay for 150 EUR.
They can be adjusted in max voltage and max current up to 3kW.
Configure your float voltage to charge to max 80% SoC.

If you can code or download from GitHub you might be able to integrate them into Cerbo. Else use Cerbo relay to switch the PSU and a SmartShunt to measure “alternator” DC charge power.

5

Detailed models from other posts.

@BjoernK and switch on : Has DC loads