We're working with a couple of systems where the production and consumption readings in VRM don't really make sense - namely, for a given period, kWh consumed far exceeds kWh produced. I'd love to get a better understanding of what might be going on.
The composition of both systems is as follows:
- Three-phase off-grid systems with PV + battery + genset
- Battery inverters (6x): Quattro 48/8000/110-2x100 rev2
- MPPT charge controllers (3x): SmartSolar Charger MPPT 250/100
- PV inverter (1x): Fronius Eco 27.0-3-S
- Diesel generator
The issue is that in the kWh Excel report (and also in the VRM UI), it appears that the energy delivered from the batteries is far greater than the energy going to them.
Example over a 30-day period:
- PV to battery: 908 kWh
- Genset to battery: 87 kWh
- Battery to consumer: 1575 kWh
It's not clear where the extra ~600 kWh come from. It's obviously not just additional discharge of the batteries, which have a capacity of ~100 kWh. Also this kind of pattern – of consumption being greater than production – is repeated on a daily basis; i.e. it's not just a one-off data glitch.
Any ideas what the culprit might be? And in the meantime, any thoughts as to whether the production or the consumption values are likely to be more reliable?
Finally, besides the two systems that exhibit this issue, there is a third with the same composition, where the readings there appear to be more consistent. In that the energy delivered from the batteries is 70-80% of the energy going into them.