Voltage drop with Multiplus 2 8000

Question

question

seine-batterien asked Mar 19, '24

Voltage drop with Multiplus 2 8000

Good day,

One of our customers had a 42 kWh battery installed and 3 Multiplus II 8000 with a Cerbo box. A phenomenon was detected at this facility.

There is a huge discrepancy when it comes to battery consumption. See AC load.

I once looked at the tensions and there is also an enormous deviation there.

The system was not installed or set up by us. From the storage to the inverter there is a DC cable of approx. 12m per inverter. A bus bar is also installed and another 3m extends from there. Is this perhaps where the problem lies? Line length?



Does anyone have a solution?

Multiplus-II

ac-last.png (46.5 KiB)

spannung.jpg (75.7 KiB)

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

108 People are following this question.

Modifications Space

Node Red Space

Answer 1 · 2024-03-20T00:13:20Z

matt1309 answered · Mar 20 at 12:13 AM

I'm not 100% on this so happy for others to tell me im wrong but would enabling Shared Voltage Sense and Shared current sense in DVCC in GX device solve the problem?

I think that'll at least remove the discrepancy. It wont however fix the losses of the system.

4

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

nickdb ♦♦ commented · Mar 20 at 05:53 AM

Do NOT enable SVS unless the battery manufacturer asks for it! It is almost always forcibly disabled on supported batteries as it can cause issues.

0 ·

matt1309 nickdb ♦♦ commented · Mar 20 at 10:53 AM

Out of Interest what are the issues?

Without having experienced them I would've guessed that issues are more likely to arises when it's off rather than on ie system is using data reported to VeBus rather than BMS.

I wouldve thought that would have more issues than using what the BMS reports, which is what i thought was used as the priority the voltage measurement if svs was enabled.

0 ·

nickdb ♦♦ matt1309 commented · Mar 20 at 11:51 AM

The typical problems that you would experience when you have an iffy or off voltage reference - issues charging, not exporting, take your pick.

This is why DVCC is explicit about using it and it is forced off.

One of my suppliers had it enabled (previously forced off) for their batteries as they had other challenges which it helped resolve.

There is a time and a place for it but in this use case not and, like many settings, it should be exercised with caution.

0 ·

matt1309 nickdb ♦♦ commented · Mar 20 at 03:59 PM

So oversimplifying SVS on, voltage per BMS is used as primary voltage measurement source?

SVS off: voltage per VeBUs is used as measurement source.

So issues tend to arise more often when relying on BMS voltage monitoring vs VeBUs?

Is my understanding correct?

0 ·

Answer 2 · 2024-03-20T00:39:00Z

Al answered · Mar 20 at 12:39 AM

Well the AC loads don't add up to the battery loads, 15m DC cables are very long runs, but not necessarily a problem if sized correctly. Setup of three phase systems have strict installation requirements, especially the cabling:

https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems

What mm2 cable was used for the 12m and 3m runs, are they sized correctly?

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Answer 3 · 2024-03-20T05:58:22Z

nickdb answered · Mar 20 at 05:58 AM

I would first check the energy meter, where is it installed and that it is configured correctly.

What battery is this? have you checked it is reporting correctly?

I would grab a clamp meter and go do some measuring onsite to see where the issue is.

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

question