I picked up the twin pack of the UV-5G Plus last week at Radioddity. The primary factor in choosing this model (my first GMRS radio) was that the batteries are chargeable via the included USB-C cable and AC adapter.
Since these batteries supply a nominal 7.4VDC to the radio, I was curious as to what the charging voltage and current was for this setup. As per the attached photo, I found the voltage and current were consistent at 5.2V and 0.7A across the entire 4-5 hour charge cycle. Since the batteries normal operating range is from 7.0v to 8.4v we can conclude that the batteries have an internal step-up circuit to boost the charge voltage to an appropriate level.
The USB charging capability will be useful in the field as I can use either the USB ports on my PowerWerx box, cell phone chargers, or truck USB ports.