Elsewhere, there's occasionally discussion relating to these cameras which, when they reach "a certain age", start forgetting things like the date and that they shouldn't flash in public.
I've determined that they have a Sanyo UT621or similar rechargeable lithium cell buried deep inside, and have posted a blow-by-blow of an E-520 repair at
https://www.dpreview.com/forums/post/65206962 . An E-500 was even easier, since the battery was accessible as soon as the camera back was removed.
MarkMLl