I checked my batteries (NP-FM500H, 7.2V, 11.8Wh rating). One that shows 88% in the camera, shows 8.21v in my Multimeter. Another at 16% in camera was 7.65v. That is normal for Li-ion batteries.
I would trust Gary Friedman as he has a lot of experience, although perhaps not as a Technician. It may be worth taking it to have it checked, not to Sony but to a local camera store. On the other hand since the A100 is now quite old and if you can afford it, get a used A350. The A700 seems to be going quite cheap and is a great camera. Either way, you will not be able to use your A100 batteries (NP-FM55H). All the Sony alpha cameras up to A77/A900 use the NP-FM500H.