Get yourself a AC Delco PRO. Make sure all connections are clean and tight. On a properly functioning charging system you should see 13.8 / 14.3 volts at idle, testing at battery cables. The GMT has a unique system. The alternator only puts out what is necessary. This helps with fuel economy. If you are in the 15's I think that it too high. You may have a problem in the alternator.
Delco makes millions of batteries a year. There are going to be some bad ones.

 

Only thing that I would buy for these trucks are stock. Nothing after market now a days are any better than stock. Spark plug places say these e3 plugs are the best blah blah blah but I would still buy new "stock" plugs. Ac delco is a good brand and it just seems like you got a bad battery. I have almost 40k (2 years) on my truck with ZERO problems.

 

well i wasnt going to update but i see this got bumped. i got a new battery and problem still persisted. seemed like short little drives without the lights on would kill the battery. it would sit for a couple days and be fine. i was leaving it at work with the main 175 amp fuse disconnected and it would still drain. im thinkin something may be going on with the starter. its been fine for the last week so ill just let it simmer a little

 

Just where is this 175 amp fuse; the dealer called it a Maxi Fuse ? They were monkeying around in there because the remote start was not working.

 

its on the firewall about a foot from the battery. so you guys know it ended up being the connection at the starter