The active charger is going to read a bit higher. In bulk its always raising the target voltage above the battery voltage to keep charge flowing.inverter was 54.4, CC 54.3 and system at 54.1
Was the FM80 calibrated with the firmware VBAT setting, or the trim pot on the circuit board in the FM80s wiring compartment?
I'm not sure about the FNDC. Mine drifts .1 or .2 in some circumstances. Usually it's in tight agreement though.