I replaced my ignition switch, but my battery keeps dying, why is that?

I have not had that checked yet.

It did not die until I replaced the parts

well,start by doing what csubak30 suggested to do first and see what readings you get,BUT you must to have a full charge on the battery to test the alternator while it is mounted on the car.or take the battery and alternator off/out of the car and take em to the ZONE,let em charge the battery,and test the alternator on their machine inside the store.