I've been impressed with the better battery time of my new iPhone 4 as compared to the 3G I had before. Yesterday evening, I finally jailbroke the 4, and the battery time today has been much worse than usual. Why is this?
I installed a very few programs from Cydia: FolderCloser, NoLockScreen, SBSettings, biteSMS, PdaNet, My3G. Note that I haven't used PdaNet yet, so I would rule that out as a culprit. Also, while My3G is set up, I haven't actually done any faux-wifi stuff today: no Skype, no wifi-only downloads, etc. I've deliberately used 3G less than on normal days, and not used wifi at all (also not as a hotspot). I've not played music at all today, in fact I've barely turned it on at all! The screen brightness is as usual, at about 70%. The phone was charged to 100% overnight as always.
Despite this, the battery is already under 40% at 5 p.m. where it would normally still be well above 60%. At this rate, I don't think it will even make it until I get home -- which is worse than the battery life of my old 3G!
What's depleting my battery faster than usual, and how can I prevent that?
Update: The first day of jailbroken battery life must have been a fluke, or was fixed by rebooting. I've been through a few cycles now and battery life seems to be practically unchanged after all.