where isa the relay switch or the charging system

I have a new battery, starter,and alternator.. I can chanrge my battery fully, and drive my car,, But, the alternator is not charging the battery... it gives me a 12.48 charge, and then runs the power out of the battery as i drive the car.. Ive checked all my fuses, and they are good.. any ideas of what this could be.. was going to check the relay switch, but not sure where it is.. Thanks