It should go to discharge if you haven't any charge going, but yes with nothing going on it should sit in the middle. Sounds like you have a little bit of charge going on but not enough to charge the battery. Could be a bad cell in the battery, or brushes in the generator getting worn or sticky, or voltage regulator sticking or not working. Not knowing what you have, its hard to tell. More info needed. New Battery? alternator or generator? Might just need to polarize the system again. Try what Jerry said first.
