Okay, this one has me stumped. I woke up this morning and powered up my PC, of which my Hero is tethered to on a daily basis when it's not in use to maintain a current charge. I checked the battery icon and noticed that in the 7.5 hours I was asleep, and it in sleep mode, it went from 100% down to 77%. I rebooted the phone and now the battery read 84%.
Usually, when it's in sleep mode for that amount of time without a charge, in sleep mode, it would read the battery at about 94-96% (I have turned off all push notifications, syncing, etc), which I feel is pretty good. This is a first.
What could be causing this phone to suddenly have a battery drop like that? I haven't changed anything in the phone since the last (many) times the drop has only been a few percentage.