Probably answered this before, but no luck with Search function on site.  I'm about to take ownership of a Big Hauler set got on ebay; 'new' but no box.  Appears this is a battery powered unit.  I've seen some dribs and drabs of info re converting to track power, including complaints that without the batteries, the engine is so light it almost flies off the track.  Adding weight shouldn't be problem.  What I'm concerned about is whether this type engine can be track powered (LGB power supply)?