First, if you look at that screen shot I provided, I did have it plugged in for a little bit there at the end. But, I've easily gotten 20 hours with medium usage (2-3 hours screen on time, streaming a couple hours of music some surfing, some testing, and a couple of phone calls.
I have made it a "full day" (18 hours) ever since I've had this beast.
Barring something wrong with your phone, either you usage pattern is a lot higher than mine or you have poor service compared to mine. Have you switched your network mode to CDMA only from CDMA/LTE?
ah, I see now what you mean. I saw where you plugged it in. Thanks for the advice on switching it to CDMA mode only