I looked at the code and I think the BIOS EC recognizes the battery model and set the voltage based on the model. And I can only find 17600 for 55Wh and 17800mV for the 61Wh in the code. Both are correct. I think it should be hard coded
However if you look over this reply and this one, you’ll find that the 55Wh exhibit the same problem, the “Desired voltage” is reported as 17400mV instead of the correct 17600mV, which is DEFINITELY a bug as NO battery for FL13 should be fully charged at 17.4V, NEITHER 55Wh nor 61Wh is limited to 17.4V charging voltage.