Studer - DC and AC voltage measurement accuracy

Ram

Dear friends,
I recently bought and installed a Swiss-made Studer grid-tie system. XTM2600 inverter and Variotrack 65 charger with a RCC-02 remote. To my surprise I find that the battery voltage readings by the Variotrack and the XTM (as shown on the RCC) differ by 0.4V for a 48 volt system which seems to be a fairly large discrepancy. The inaccuracy is not just the display - it is also in the data log. (Readings were taken at night when Variotrack current was zero and the battery draw was also zero to eliminate cable losses). I also find that the AC-In voltage reading is about 5 volts higher than my Class 1 energy meter at 230V - an error of 2%. The Taiwan-made Axpert inverter manual says DC voltage accuracy is +/- 0.3% so I am left wondering why a Swiss-made product cannot do better. Any observations from other Studer owners (there are a few on this forum I believe) or users of other reputed systems on whether such inaccuracy is considered "normal"?
Best - Ram
Bangalore, India

mvas

+/- 0.3% ...
48 volts x 1.003 = 48.144 volts 
48 volts x 0.997 = 47.856 volts
48.144 - 47.856 = 0.288 volt difference, round up to 0.3 volts difference.
You show a 0.4 volt difference, which not significantly worse.

Is there any voltage drop caused by connections or cables?

Maintaining +/-0.3% for more than 1 year is not easy, without re-calibration.