Some preliminary information:
I have several systems but only one with this issue.The affected system consists of a multiplus, bmv-712, two 100/30 charge controllers, and a cerbo gx. The battery is a custom 11kwh lithium iron phosphate battery. The BMS on that battery maintains normal charge level indications. There are no loads or chargers that do not go through the bmv. Peukert exponent is set to 1.
The issue:
In VRM the consumption kwh always shows about 10-20% more than the solar production. Day after day. If this were the case the battery would be slowly depleting, which is what the BMV shows, but that is not the case. The BMS on the battery shows that it is returning to 100% every morning. But the BMV will show it only returning to 99.8%. The next day will be 99.7%. The day after will be 99.6% and so on until I get irritated and reset the SOC in the bmv back to 100%
The system mostly sits idle and there is plenty of excess solar capacity that is not being used. I have tried disconnecting all charging and loads and resetting the current calibration on the bmv.
The more power I use, the higher the difference becomes. On idle days it's usually a difference of .5kwh. On days where I use 5-6 kwh the difference can be as much as 1.5kwh. If I use power after dark the discrepancy will show up the next day.
All of this leads me to believe that one or both charge controllers are actually delivering more power than they report. Is this possible? Is there a way to calibrate them? Shouldn't the bmv be counting the actual incomimg charge anyway? Or am I possibly missing something in the battery setup?