question

@John Bannell

If I am understanding you correctly you want to differentiate between solar charging the battery and mains charging? The inverter has no way to measure that internally. It can however measure power in from grid.

It is a difficult thing to determine as well as there are losses in charging and each system is different in this regard. But really the amount is what was discharged out of the battery in the first place.

Thank you for your response.

You will forgive me but solar goes into the battery and also mains power goes into the battery via the charger. (this enables the standard process of 'time shifting') If I can't tell how much Mains power has been put in I cant optimize and balance the levels at which the off-peak start of charge level is set, or the charge current rate.

Mains power into the Battery is controlled by the Multiplus, and, as I understand it, once triggered by the 'start charge level' set in my CCGX, mains power is then shoveled into the battery at the programmed charge rate, which is (battery spec permitting) up to the maximum capable from my Multiplus - 70A.

(I am running a 400+ AH Lithium Ion pack, so charge current limitations are not a problem)

Currently I have the charge level set (by Victron Connect in the Multiplus) at 50A, and this appears to agree very closely with the mains power levels displayed and visible within the 'advanced' displays.

The Multiplus II has, as I understand it, an internal Current Sensor, and of course has a real time Battery Voltage Sensor. It should, therefore, be able to to tell pretty accurately how much power has been put into the battery during the off-peak charging period. This would be 'actual power into the battery'. The CCGX and Multiplus know exactly when charging starts and stops and integrating Real Time Power is a very easy calculation.

I appreciate that no battery is perfect, and that there is some loss between the Charging and Discharging process. This is particularly true for Lead Acid Batteries where some people might well wonder why we use them for Energy storage applications! This is not the question.

The question is 'why does the software seem to be unable to recognize and display 'Direct Mains Power battery charging energy' as it already can and does for charging by a separate Gen Set? My problem is that my battery is not ''top-up-charged" by a Gen Set, it is 'top-up-charged' charged by the Mains. With a Gen Set system, it is a pretty necessary function to know how much power the gen set has supplied - why is this not the case with Mains Charging? Is there any way that this can be done?

Easiest way is to define the AC input as generator and use the statistics if you are happy with it.

@John Bannell yes I believe this is a fundamental flaw. The System Overview in the VRM dashboard is in principle correct (for a system without storage!), the basic equation is that

From Grid + Production = Consumption + To Grid

and you can re-arrange this to read either

From Grid - To Grid = net import = Consumption - Production

or alternatively

Production - To Grid = own use = Consumption - From Grid

but I have often wondered why over say 2 days the figures can be out by several kWh. I think you have hit the nail on the head, in that the discrepancies are probably accounted for by the delta SoC between the start and end of the period of measurement, I will look at my stats to see if it explains it. The full equation should obviously be

From Grid + Production = Consumption + To Grid + increase in SoC

What can be done about it is a different matter. Over the long run the error will at most be the capacity of the battery so pales into insignificance compared with readings over a month or a year. I have a separate bidirectional import/export meter and the original FIT meter as well as the supplier's meter so I don't rely on reconciling the Victron measurements.

And some 10-15% losses for charge efficiency, dc to ac transformation, heat

Thanks,

It helps to know that I am not completely bonkers. It also strikes me that as we move to distributed storage unless the information supplied by the system is reasonably correct, and properly accounts for the 'from grid to battery' energy, it is really poorly adapted to do the job at hand with what will become more the norm - Time Shifting/Solar/Battery systems

Any Bright ideas on how we get Victron to look at this - I have been trying for over 2 years and have only got a 'go away' response from everyone!

I have a smart meter which will report every half hour, a FIT Meter, and a 3 phase Consumer meter measuring power from all solar and house in/out. Since the Multplus/CCGX is the hub that controls everything - shouldn't it be reporting a true picture of what is going on?