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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.

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Welcome to Jailbroken world. That’s the reason why some of those apps and services aren’t allowed in the iPhone “by default”. The iOS is heavily tweaked to maximize battery power. Multitask happens in a very controlled environment. Anything outside that (like those apps) will definitively deplete the battery faster. In any case, restart your device, there might be a hung process eating phone’s CPU. –  Martín Marconcini Oct 20 '10 at 20:45
    
This happened to me as we'll... Except on iPod. If anyone knows how to fixit without having to take out all the other jailbreak tweaks that would be great... Btw I've already tried rebooting –  user44751 Mar 9 '13 at 23:43
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2 Answers

up vote 9 down vote accepted

I can see two main possibilities:

  1. Apps like FolderCloser, NoLockScreen, and SBSettings shorten battery life by requiring heavy background processes. The only solution to this would be either to not install these apps or restore the phone to its original state altogether (and not have these apps installed). I am convinced that jailbreaking allows for processes that are not in phase with Apple's careful thriftiness of battery use.

  2. Your battery is not calibrated properly so your iPhone miscalculates the remaining percentage. The solution here would be to drain your battery completely and then fully charge it.

Good luck! And know that you can restore the phone to its original state.

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you guess these apps use more process or you know? it's was interesting for me to find a list of resource that used per apps. –  Am1rr3zA Oct 20 '10 at 16:35
    
I know these apps increase the overall use of background processes. How significant this is will depend on the app. –  sentinel Oct 20 '10 at 17:02
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I think many of the jailbroken apps continue to run using a full multitasking approach. This is different than the iOS multitasking, which just keeps apps in ram, etc. Those apps staying open, and even using very little processing power, would be using extra processor cycles, therefore depleting faster.

Also (I haven't jailbroken before), the jailbroken iOS may even be running more services in the background than a normal iOS install.

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