battery going dead

I have a 02 chevy Tahoe 4x4, the battery goes dead after about 7 days. I have already replaced the battery 3 times There are no lights on and I have double checked this. Does anyone have any ideas???

i would have the alternator checked..it is a very simple operation, and any shop that does battery replacement should offer a free or VERY cheap alternator test, and it only takes a few minues, IF that.  if i recall correctly, and if you are fairly mechanically inclined, changing the alternator on that vehicle is not very hard. Patrick38435.5533564815