Multiplus 2 GX and Multiplus 2 Parallel Issue

DIY
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1

Hello everyone!
New Victron user here, I’ll try to be as brief and clear as possible.

My system consists of:

  • 7.2 kW of solar panels
  • 1x MPPT RS 450/100
  • 1x MultiPlus-II GX 5000VA
  • 1x BasenGreen 230Ah battery
  • 1x SmartShunt
  • ESS assistant enabled

I installed and configured everything in September 2023, and it has been running very efficiently up until now. So, I decided to expand the system by adding a second MultiPlus-II in parallel. Since my first unit has a GX, I purchased a standard MultiPlus-II 48/5000 as the second unit.

Now, onto the wiring:

  • On the DC side, I carefully made sure that all cables are of the same length and gauge.
  • On the AC IN side, same attention to detail, ensuring symmetry.
  • On the AC OUT side, the only difference is that the AC OUT cable for the second Multi is about 20 cm longer than the first one, but I don’t think this is the cause of the issue.

I wired AC IN in parallel and AC OUT in parallel, then started the configuration using VE.Bus Config:

  • Set both inverters to L1, with the GX unit as the master.
  • Then, I proceeded with VEConfig, applying the exact same settings from my MultiPlus GX to the new MultiPlus-II.
  • I also loaded the ESS assistant and halved the AC input current limit from 32A to 16A, since I now have two MultiPlus units.

Now, here’s the issue that’s driving me crazy:

  • Both MultiPlus units turn on, the new MultiPlus-II blinks as a slave, but the first MultiPlus-II GX becomes very noisy.
  • Despite not being connected to the house loads, they draw power from the grid erratically, fluctuating from 300W to 1100W in a second, then dropping to 50W.
  • The VE.Bus Info Monitor does not show any issues with the grid frequency or input voltage.

I have also upload a video to provide more details.

Additionally, here are the details for both units:

Serial Numbers :

MultiPlus-II GX: HQ2306N
MultiPlus-II: HQ2343Z

Part Numbers:

MultiPlus-II GX: PMP482506000
MultiPlus-II: PMP482505012

I know they should match, but since one is a MultiPlus-II GX and the other is a standard MultiPlus-II, is it normal for them to be slightly different?

Additionally, I opened the chassis and checked the numbers on the internal boards to verify compatibility. Both units have the same board number: 2623498.VFD .

I really can’t figure out

2

That 20cm could just be the issue… parallel can be hard to run right, model/date should not be a problem

3

Thanks! I’ll adjust that too and see if it fixes the problem.