I'm having trouble isolating the issue causing my Note 2 battery to drain, and I think it's related to the screen usage somehow. Details inside.
The problem seems to have started or escalated sharply a few days ago, when I noticed the battery was draining much more quickly than normal and was getting noticeably warmer than normal - I could feel it through the battery case. Before a few days ago, I could normally go 18ish hours on a full charge, while using the phone moderately to browse the web, stream media, navigate using Maps, etc. Now I'm down to 3-6 hours, depending on usage.
a few screenshots of GSAM battery monitor over a 4.5-hour test period today. During this time, my phone remained sitting in one place, on my desk at work. Wi-fi, GPS, and bluetooth were all turned off. I received some text messages and two short phone calls. I wasn't actively browsing the web, no downloads, no videos playing, no streaming of any media.
From the battery usage stats, the screen seems to be sucking up a lot more power than it should. The battery usage numbers for the screen seem really high: 52.3% battery used for less than 20 minutes of use. I have my phone set to timeout the screen with 2 minutes of inactivity, but I always put the screen to sleep manually when I'm done using it, including during the test period. I did have the phone on max brightness during the test period, but this is normal use for me and shouldn't be the cause of the problem. I use the Lux Lite app to manually manage screen brightness. I haven't noticed any abnormal behavior from the screen since the problem seems to have started.
The other stats (phone, phone radio, app usage, held awake) seem to be relatively normal, and don't appear to be unduly draining the battery. But if you disagree, please educate me. I'm not used to troubleshooting phone issues.
Other info that may or may not be relevant: The phone is a SGH-T889 model, T-Mobile, Android v4.1.2. I am running Nova Launcher and a live wallpaper, but I've been using them both continually for a couple months prior to the problem popping up. I have a 1-month old spare battery and the stock battery that came with the phone when purchased in November 2012, and the problem seems to be the same regardless of which battery is in the phone.