Is it normal for my LG K10 to go from 100% to 80% in 1 hour and 30 minutes.

[AC Question]

I got my K10 three days ago (7/7/16), and I've been worried about the battery. I guess you could say I've been obsessing over it. It stays a 100% for about 10 to 20 minutes, then the percentage starts to drop. It usually takes 1.5 to 2 minutes for my battery percentage to drop. I'm wondering if this is normal for a new phone. By the way, I didn't let it charge all the way to 100% when I first got it. Is that bad too?

 

[belodion]

Welcome.
Some phones will show 100% battery charge for a surprisingly long time in use before dropping to 99%. I know from personal experience that the LG G3 and G4 do it.
Your rate of discharge sounds okay, and so far as I know, not charging fully the first time is harmless.
This Guide may be of interest to you: http://forums.androidcentral.com/showthread.php?t=500054