I had reinstalled my phone (3Gs) from scratch and jailbroke it with Blackra1n then installed and set everything up again only to be massively dismayed that the battery was 1/3 or 1/4 what it used to be. I used to be able to go 20 hours standby and 4 hours usage before I needed to recharge (which isn't stellar to begin with but it was doable for me.) I would literally watch my battery tick away while using it and it would only last half a day with 2 hours usage.
I searched the forum and read a large number of fixes and suggestions. I saw that Rotation Inhibitor was a fairly common issue for some but I'm not using that at all. Others had problems with Winterboard and/or SBSettings (two things I do use but had used before with expected results. It does drain the battery more than without but not an unreasonable amount... at least for me.)
So I did two of the easier suggestions I ran across that corroborated with Apple support in some cases:
- Turned off Push, power cycle and turned it back on.
- Allow the battery to drain until it shuts off then recharge to a full 100% before using again.
This worked like a champ. It may have been one or the other... maybe even a little of both. Things did seem to improve greatly with the first change and I figured doing the second wouldn't hurt and may even potentially help. I'm currently sitting at 69% battery after 2 hours use and 10 hours standby. Just yesterday this amount of usage would have required me to start recharging as I would be in the red.
Good luck to those with trouble still, hopefully this works and if not I hope you find the fix you need.