On my drive the other day I watched my normal voltage of 13.5 start to go down to 12.7 and stay there while driving. Stayed that way for about 10 minutes but whenever I stopped it went back to 13.5. So I seemed to recall that the BMS would do a periodic calibration . Went into the service manual and found that when the calibration started the battery voltage would go down to 12.5 during this period . So for those of us with the 5.0 it's something to remember if you monitor your battery voltage .