Alkaline batteries
I wouldn't recommend alkaline batteries for the F2 because they often leak out corrosive liquids even when their power output is still good. I would recommend 3V lithium batteries, as I have never heard or found them leaked. If you use alkaline or silver oxide batteries, then regularly check they are not leaking or sweating.
Even branded batteries leak
These batteries were still producing 1.477V
and passed the DP-1/11 battery check
Battery liquids seeped into
the battery contact and tag
The battery tag was corroded
and full power could not get to the finder