In theory yes, but a long time ago there were reports of it working very ineffeciently! I've never used it, always charged the battery in the supplied charger (or a third party one). the smaller NP-95 batteries (as opposed to the later NP-W126) don't last that long in the camera, so a spare is almost essential, but if you use the OVF and don't chimp they can last a surprisingly long time. As
@trevorbray said, the battery usage meter is next to useless, expect it to show nearly full/full most of the time, dropping significantly for the last 20 shots!
The EVFs on early Fuji X series cameras were not super bright, and suffer from slow update and limited number of colours shown, many prefer the OVF even though the number of focus points is reduced. The OVF also allows a view beyond the frame, so you are pre-empted about targets entering the frame. Bear in mind as well that the Highlight/Shadow settings have an effect on the EVF image (and JPG), so make sure these are set to your liking
The X100S is a little pedestrian (not as bad as the original X100) but it more than makes up for it with the IQ.