Why does your battery keep draining in your 1996 Chevy Venture minivan?

Usually only two reasons for this. Either the charging system isn't properly functioning or there is something on that shoudnt be. The latter is usually a glove box light or under hood light that doesnt shut off. The charging system could be either the battery or the alternator. Have this checked. That is the easiest way. Usually somplace like Auto Zone will do this for free. Usually though the battery is going bad and not taking full charge or just not holding charge. I hope this helps. Brad.