Yes, a Ryobi battery purchased today does have a serial number printed on a sticker on the battery. There are usually located on a black label in a white box.
The older Ryobi batteries however do not show the serial number of the battery, only the month and year of the manufacturer of the battery. I have a battery from 2012 that I still use that doesn’t have the serial number on it. I’m not sure when they started printing serial numbers on all new Ryobi batteries.
See the below images to see where the serial numbers are located on 36.0V and 18.0V batteries.
Related:
Where is the Ryobi 18.0V Battery Serial Number?
Where is the Ryobi 36.0V Battery Serial Number?
