is it possible to do a zero current calibration on a lithium battery which is not connected to the RV yet? The only connections would be the negative battery terminal bolt to the battery minus side on the shunt and red cable from Vbat+ on the shunt to the positive battery terminal bolt. Or does there still have to be a positive system connection from the RV to the positive battery terminal bolt?
No, even without the plus connection to the rv the current will be zero 
I am confused. Don’t I want the battery current to be zero in order to calibrate the SmartShunt to zero?
If you remove plus or minus or both from battery the current IS zero !!!
Connect the battery negative pole of the shunt to the battery negative and the positive signal wire to the battery positive, connect nothing else to the shunt or battery, you will have zero current through the shunt, do the zero current calibration.
Thank you very much