Battery-tracking app
Wakelock detector should show you if there is one (or more) apps keeping your phone awake overnight.

You could also (if you're rooted) try BetterBatteryStats. It's a paid app but it can be found on XDA if you want to try it out (The thread was started by the author). I've included their message on why they make it available free on XDA below. 


  BetterBatteryStats is available on the Android market for what I
  believe is a fair price. If you like my work and want to support me
  please fell free to show your gratitude by buying the app.