I was stuck in training for the past two days and couldn't leave the phone plugged in like I do at my desk. Late in the day it was getting low, so I turned off WiFi and mobile data (G4 data) and set it to power-saving mode, figuring I wasn't surfing or checking email during the sessions anyway.

Today I decided to leave power-saving on, and when I got to work I turned off mobile data but turned on WiFi. It's now 2:44 and I'm still at 78%. Normally I'd expect to be somewhere around 45% by now. In the battery graph, I can clearly see the charge line flatten out when I turn off mobile data.