On 14/9/2024 Octopus Energy offered 1 hour of free electricity. I set up my system to charge the batteries and run several domestic appliances. At the end of that hour the ‘from grid’ data in the VRM dashboard was simply incorrect, ie 6.2kWh whereas the real figure was 9kWh. Does anyone have any explanation?
For the past two years, under normal circumstances, this data has seemed 100% reasonable. I appreciate the current sensor sensitivity affects accuracy for low loads, an that the power readings are affected by reactive loads. During this 1 hour period approximately 6kW was used to charge the batteries, and the heating appliances added a variable load averaging ~3kW peaking at 7kW.
I have attached a layout schematic showing the multiplus ACin connected to the grid. All loads, etc are connected to ACout.
The smart meter data downloaded from the online data bank confirms the readings taken from the smart meter in the property.
The RHS numbers 4.225 & 4.812 show the energy used in each half hour in kWh.
The input voltage and current graph also confirms ~9kWh, ie the system had the correct data.
The question is: What did the meter report to the cerbo? (How is it connected, what kind of meter is it?)
The Figure From-Grid is computed by the offsets of the /Grid/Ac/Energy/Forward-Value reported on dbus by the meter:
You can go to the advanced view in vrm, and generate a graph for this value (Grid total energy from net), which you then can inspect for the given day. (Just save the widget, then browse to the day in the advanced view and the widget will adapt its timerange):
This is, where VRM gets the data from. If this value is “wrong”, you have to analyze, why the meter (or the responsible script) is sending wrong data to /Grid/Ac/Energy/Forward.
Thanks @dognose for responding, and for the detailed directions you gave.
The ‘smart meter’ I refered to is the DNO smart meter for the house which is not part of the Victron system and does not communicate with it in any way.
As the multiplus ACin is connected directly to the grid there is no energy meter connected to the system. I understand all mains related data is collected via the Mulitplus current sensor, voltage sensor, frquency sensor, etc. Apart from that single 1hour event all previous data on the dashboard has made sense.
I can find no ‘grid total energy’ type option on the advanced page, but as I tried to illustrate with the screendumps, all the graphical data I can view supports the actual use of ~9kW. Just puzzled as to why the ‘from grid’ summary box is so far off. I wonder whether it is to do with the unusually high charging power/current I was using. For the past 2 years overnight charging has been set at ~ 1.5kW.
During the hour slot in question all ‘live data’ on the vrm dashboard was correct. It just does not seem to have added them up correctly for the ‘from grid’ summary - as if there is a bug somewhere in the software!?
Ah, thought you have the meter connected with the cerbo and wonder about the differences.
Well, then all the above does not apply.
Unfortunately I can’t tell you anything about the accuracy of the MPs internal sensors to count energy - and how it’s done. So can’t tell why there might be differences in this case.
Yeh, unless someone from Victron can light on this I think it will remain a mystery. Not really a problem forme, but carrying out calculations is the one thing that software is very good at!
