VRM Showing strange values (like energy disappearing from BYD battery-box

Q&A and troubleshooting
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1

Hello,

I have three Victron Energy MultiPlus-II 48V/5000VA with Cerbo GX and BYD Battery-Box LVS 16.0. The system is running for 9 months now. Looking at the VRM dashboard, it shows numbers, that do not make sense to me:

  • If I take a period (like 24 hours), where at the beginning and at the end of the period the charged capacity of the battery is the same (10%) I would expect that the sum of the values (From Grid + Solar - To Grid - Consumption) is somewhere close to 0. Instead it is usually 2,5 to 3 kWh.
  • The minimum SoC is set to 10%. According to VRM it goes frequently to 7% or even 6% during the night. In these hours, where it drops bellow 10%, the load from grid is even higher than consumption.

I am no expert, just consumer, but it seems to me, that energy is being lost somewhere.

My vendor of the whole system states, that they checked the battery box and it is ok, and the problem is in the data reported by VRM. And that Victron company is not responding to the issue.

Does anybody have similar problem or even the solution?

2

I have seen something similar on a different battery make.

We came up with a few theories in various discussions.

One of them of you understand how ohms law affects a battery bank will add to the sense.

If it is a few batteries stacked sometimes their aggregation is not quite right on soc. When left idle they then sort of do little discharges into each other and ‘balance out’ for lack of a better way of explaining and then their overall soc is not the set amount. We had measured that movement ourselves and it was not reported to the GX the battery remained ‘idle’.

And the victron inverters will only be seeing voltage which is pretty much flat at that soc. I know there is a GX but it is not quite as cut and dried as that.

The other one is the inverter system own self consumption is pulled from the battery bank while loads are pulled from grid, so can slow drain a battery like that. I can’t remember if that is included in the consumption figure or not. But theoretically the battery would be reporting that slow drain with a few watts darwing out if it is good at reading those smaller drains in power. You would be able to verify that with your vrm data.

I would be keen to hear if anyone has other ideas.