iPhone 3G With iOS 4 Battery Life / Performance Bug

There’s been various reports of poor battery life in particular with the iPhone 3G and iOS 4. After updating I noticed battery life was reduced for my phone, but not as bad as many others were reporting (I’d say a ~15% reduction in battery life). I did however find what appears to be a fix. It’s quite simple actually.

Plug in your iPhone 3G either to the wall charger or your computer’s USB port and let it charge while on for several hours (overnight should be cool). Power down your phone, then turn it back on. For me this brought the phone’s battery life back to where it was before the update.

Why does this fix work? I’m not sure but I do have a theory. It appears when the OS was upgraded your spotlight database needed to be updated. This requires indexing all the data on your phone. Needless to say all this effort kills your battery. Apple must have some algorithm in place to do this work and preserve battery life but it obviously changed between iOS 3 and iOS 4. By leaving it plugged in it appears to complete the process and by restarting it will make sure that any hanging process on your phone is killed and memory fragmentation is cleaned up. iOS 4 runs tight, swapping kills performance and battery life. This also seems to help performance as my phone doesn’t lag as much anymore (though it’s hardly a speedster like the iPhone 4). It also explains why some people would see different levels of the problem as it would depend on how much you have to index.

Let me know if this fix works for you.

19 thoughts on “iPhone 3G With iOS 4 Battery Life / Performance Bug

  1. No, I’m sorry to say it didn’t help at all.. My 3G has 20% battery life left on it at this exact moment, and it has only been off the charger for 5 hours and no use on it.. Something is completely wrong…

  2. great tip!

    worked with my 3Gs

    I have been having some problems with the battery life of my 3gs even since the iOS 4 update.
    Would set my alarm for the morning and on the next day had dead iphone twice, meaning no alarm :/
    Before iOS 4 this had NEVER been a problem… so it was obvious some process was eating up the battery live…

    After reading your post I charged my iphone for I would guess 5 or 6 hours, did a shut down & restart and
    voila all good again! Woke up on time this morning!

    May thanks before reading this I was already looking in how to replace the battery :))

  3. This didn’t help me at all. Matter of fact, ever since the update, my battery life is not updated unless I turn off and on the iPhone. My battery dies half way through a work day, though I have most items turned off. And I don’t mean low on power, I mean completely dead. When I attach the power charger, the batter can charge all afternoon, but when I unplug the phone, it shows the battery is still dead If I power cycle the phone, when it is powered back up, it shows a full charge. Then half way through the night, before 10 PM, the battery is dead again, though I am typically looking at email, etc by then. Before the OS update, the phone would work all day and night without a recharge.

    With the poor AT&T service AND the poor battery life, I plan to replace it once the service agreement has expired, though a iPhone 4 with AT&T is not in my plans. Apple needs to divorce itself from AT&T before I buy another Apple phone.

  4. My 3G phone also is a battery hog now after the 4.0 update. It even seems to be hotter to the touch even when it isn’t plugged in. That tells me the battery is draining quickly for some reason. Fully charged it overnight and when i unplugged it at 9am by noon it was telling me to plug it in by 1 it was dead.

    Something must be totally wrong. I am going to try to wipe it clean and reinstall as if the phone were a new phone. Then check the battery life.

  5. I noticed my 3gs battery draining faster after the iOS4 update, too. The fix I tried was to let the battery run completely down, to the point where it shuts itself off. I then charged it back up again overnight. That seemed to do the trick, which made me very happy. (The next fix I was going to try, if that didn’t work, was to do a restore and I really didn’t want to go through that).

  6. I am having the same problems with battery life. However, I believe it has to do with a specific application. I did a restore of my phone on Friday and didn’t have any problems all weekend, but today my phone dropped from 90% to 15% within 3 hours with no usage.

    I believe there is an application that has not been updated for iOS 4.0 that is not completely shutting down when closing and, therefore, running down the battery.

    I have heard that setting your 3G or 3GS up as a new phone may fix the issue as well.
    Apple support was no help.

  7. This worked for me – thanks! I plugged my iPhone 3G in last night for 4 hours & then powered it off for 10 minutes. This morning after an hour of use, it seems to have the same battery life it did prior to the iOS 4 upgrade, which is to say: after an hour of use, there’s no noticeable battery loss, as there had been after the upgrade.

    Fingers crossed — and thanks!

  8. OMG, it looks like it’s really a bug. Well, I’ve done this for about an hour and it seems fine now. Ok, Now everything you have to do is:
    1)Charge your iPhone until it gets 100% and the lightinh symbol disappears.
    2)Turn it off While still plugged in the wallcharger
    3)Remove the Wallcharger and wait about 10 minutes
    4)Turn it on and have fun.

  9. This doesn’t help me at all. I feel like I’m always charging the battery but it drains in a couple of hours and the iphone shutsdown when I have 50% of the battery life still available. Sometimes I can’t even take a picture, if the battery is not charged 100% or the phone shutsdown and it won’t turn on unless I start charging it again. The weird thing is that sometimes when it shutsdown when the battery shows 50% of the its life available, if I start charging it , then it shows on the screen the battery fully empty and red. It’s like the battery indicator shows the wrong thing.

  10. I have tried the full drain, full charge and reset and it has improved, i.e. I can now at least get through the day with some battery left, but it still has much less than before the iOS4 update.

    My thoughts are that it is one (or more) apps causing the problem – possibly Skype but this has been updated for iOS4. Perhaps it has bugs?

    I held off updating to iOS4 on my iPhone 3GS because of all the problems I’d heard about. A friend convinced me theirs was fine and showed me a couple of new tricks in the iOS4 and so I bit the bullet and did the update. I wish I didn’t!! I was completely happy with iOS3! Does anyone know how to go back to iOS3 without having to restore all of the data?? 😉

  11. I have the same problem. A restore fixed it for a week or so, but it came back. It seems to have begun both times while using the native email app in the “all inboxes” section. I noticed it hanging on retrieving an email from ms exchange both times and after that it was downhill pretty quickly.

    This combined with AT&T’s horrid service is making me want to move to droid.

  12. Damn upgrade!

    I have two iphone in my hands right now. 3G 8 and 16GB. Both upgraded to 4.0 and both draining the battery.
    I tried all of above with no result. It seems like it stop sucking battery when I take the sim out of the phone.
    I turn all off (notifications, push, etc) but still.
    Really don’t know what to do, it used the full battery in 3 hours doing nothing. It felt it was warm but not sure since it was in my pocket.
    Apple is not helping I see, that is disappointing.

  13. New update… don’t know what happen… I am trying to fully recharge it now just to be sure, but seems like is working. I restored it again (but I did it before and wasn’t helping) and turn everything i can off, installed only the basic apps and made mail (mobile be too) run and download emails. No push yet and manual fetch. Wifi off and cellular data off. It worked. So i tried to turn wifi on and cell data on (location is still off) to drain the battery 100% but it didn’t, I mean, it did eventually but not as fast as I was expecting.
    Is it the battery memory? Some app? The location or the wifi/data? It surely stay on for ever when wifi is off and sim off the phone, so there’s definitely a connection there. I just need to find out what is it. A big pain in the neck and hours and hours of precious time wasted.
    Plus, if I want to buy the 4G the antenna has problem too, so what is the solution? I use my phone for work and this isn’t the way I usually work. Apple? Can you read?

  14. I’ve had lots of strange problems with my 3G since I downloaded the iOS 4. I called AT&T and they told me there were bugs that an additional download would fix. Now things are even worse. Don’t plan on renewing my contract or getting another iPhone. There’s gotta be something better out there.

  15. Hi, I am having the same problem with my iPhone 3G I upgraded it to iOS 4 and It is draining the battery, I can only use the phone for only 4-5 hours max. I tried Fully charging all night but the problem is still there…. Is there any other way of fixing this problem??

  16. Hi there, I have been facing battery proems with my iPhone 3G a
    D now it went back to normal. Try the following
    1backup all the applications on your iTunes
    2 remove all the applications from your iPhone
    3 shut fully charge your iPhone and there you go.

    I realized that some of the applications I have installed are the problems. They were not compatible with iOS 4
    I will let you know which ones later.

  17. I have the same problem. Have restored system, as Apple advised (!) (what a pain), but problem remains despite removing Skype.
    Apple should acknowledge the bug and until it is fixed offer a way of reinstalling earlier systems. Why don’t they???

  18. Apparently the indexing issue running in the background is the issue indeed. Trying to do too much with too little harddrive I suspect. I have checked over and over the different blogs about this and I am considering downgrading to iOS 3.1.3 It looks like most of the features added by iOS 4xx are nothing that I really need. If I dare, I can always do a whited00r jb and this will emulate a few features of iOS 5xx even such as multitasking and iCloud functionality. But first I try your suggestion and sort out all of my apps, some of which I bought with my original 2g iPhone.

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