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:
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 .
@SimP , Switching of parallel systems is carried out only through cross modules, with the same cable cross-section and length, also all protective automation at the input and output must be identical and have the same resistance!
Hi,
Unfortunately, I haven’t managed to solve the issue yet.
After the initial problems, I completely rewired the system to ensure perfect symmetry:
All DC and AC cables are now the same length and cross-section.
MultiPlus-II units are connected through identical circuit breakers and protection devices.
The VE.Bus setup is correct, with the GX unit as Master and the second unit as Slave. Version and internal board numbers are also identical.
Despite all this, the strange behavior persists: the GX unit still makes unusual noise, and the power draw from the grid keeps fluctuating erratically, even when low power loads are connected.
At this point, the only thing I haven’t tried yet is installing a Carlo Gavazzi grid meter to see if it helps with balancing the grid pull, with the ESS.
In your design isn’t necessary required the external grid meter, just simply external current sensor (CT). Have you installed it & activated in VE config? If so, then you first need to focus on the resistance measurement of each chain AC IN / AC OUT.
Which do you use cross-section wires for AC IN / AC OUT?
UPD: For example, 4 x MP2(5kVA) paralleling system that meets safety standards & most Grid codes. (This is only parallel connection, without distribution)
