One problem related to battery has been reported for the 1998 Volkswagen Passat. The most recently reported issues are listed below.
Fire in rubber boot housing between left rear door and car frame. Preceding events, left rear door speaker was not functioning, left rear window functioned sometimes. Door was closed after returning home and parking garage. Arcing was heard and smoke came from door. Owner removed many fuses from drivers side fuse panel and then removed connections to main battery. Door panel cover was removed and boot removed to find housing on 5 of the 8 wires burnt and most of the wire burnt through the wire. Pictures are available.