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ISO is displayed on the top panel, is it not?
From what I understand, the data missing from the top LCD is pushed to the rear screen, so when you push the left button for Picture Control, Quality or WB (all of these), the rear display lights up and shows those settings. Might explain its greater battery demands if you adjust things that way. I would guess that WiFi is the biggest new battery drain. One way to test is to disable it in settings and see how your mileage goes.
Sorry guys, posted in a hurry and have been out all day.I meant white balance not ISO. I know it pops up on the rear screen, and I am starting to get used to it more but I still prefer the D7100 at the moment.My wi-fi is always off until I need it so it isn't wi-fi that is the culprit.
Sounds like normal behaviour for a new battery, it takes a number of full charge cycles (10-20) before the battery starts operating at peak efficiency, and should keep to that level until there are 200+ cycles.
Des Monies IA