Considering your situation where you may have done this already...
Run your iPhone until it shuts off due to low battery. Wait a few minutes, turn it on and let it shut off again. Repeat a few times to fully discharge the battery.
Now fully charge to 100%. This should recalibrate the battery meter but you may need to do this a few times.
If this doesn't work, you can try to restore via iTunes.
None of these fixes work for me. My 3GS is 1 1/2 yrs old. Ancient in Apple's eyes. I'm sure Apple wants us to just go buy another iphone. It increases their stock value.... And drains my wallet!
I turned off all apps running in background and now I turned off Mobile Me to test if that app is my battery drainer. I hope I don't need to use Find My IPhone app today!
The 3gs battery at Ifixit.com is out of stock right now; I'm seriously considering a battery replacement.
I have tried this a few times. However, in order to charge the iPhone, I use a Bose SoundDock. Perhaps this is the problem and in order to rest the battery percentage indicator, I need to use an Apple wall charger?
You should try charging with the Apple wall charger for 4 hours after you have run it all the way down. If you still have a problem you probably need to replace the battery, but take it to an Apple store and they can test the battery for you so you will know for sure.
I'm experiencing the exact same problem even though it has came and gone and seems to be related to iOS updates. The battery has been working fine for a long time and then right after I’ve installed a new iOS version the battery has gone from 40% to empty in seconds. After yet another iOS update it has been fine again. I have no evidence to support that the iOS installations are causing/fixing this, but it looks like a pattern.
I have the 3Gs now with iOS 4.3.5 build 8L1. It has never been jailbreaked.
My iPhone 3GS has recently started showing the exact same symptoms- battery drain seems normal, but when battery indicator hits 39-40%, the iPhone suddenly shuts down. Pressing the power button starts to reboot but then it shuts down again. Repeat a couple times, then it will no longer even try to boot and will show red low battery indicator, until it's plugged in and charged for a while
On most days I don't run into the problem because I might only run the phone down to 50~60% or so before getting home, then I always charge it overnight before using the next day. But the problem shows up at the worst time, e.g. a few times out of town on vacation, relying heavily on Internet and gps/maps usage to find my way around then I easily drained the battery to 40% during the day
I'm guessing this is just a sign of a dying iPhone battery. My iPhone is now 2yrs 2months old.
I saw a very similar pattern with my last MacBook Pro battery which would look fine until it got to 30-ish % then would suddenly drop to zero. A trip to the Genius bar confirmed that MBP battery needed replacement. They had a diagnostic tool to quickly check the battery health
Does anyone know it they have some kind of similar diagnostic test to confirm the iPhone battery health?
- tried Restore from Backup - problem remained
- went to Apple Store, with my iPhone already run down to about 50% battery
- Genius Bar guy ran a quick diagnostic test over USB cable - test indicated battery OK and he said it could simply be a software problem, i.e. battery indicator might not be showing the correct value. (I didn't believe his diagnosis)
he insisted we do a full, clean Restore, since I had only done a restore from backup previously. he said maybe the problem was just being restored from backup.
Then wanted to send me home and use the iPhone in that cleanly restored state for a while.
But not wanting to make another trip back, I refused to leave the store; instead I stayed while he served some other customers and ran the battery down, on my own time. I was 100% sure it would die again.
sure enough, the iPhone promptly died again just below the 50% mark, while watching some youtube videos over wifi.
showed this to the "Genius", and he finally agreed the battery was dying and needed replacement.
Battery replacement fee = $89 (unfortunately, my Applecare coverage expired 2 months ago)
but for some reason, he said they don't do battery replacements in-store. Instead, for the same $89 fee he swapped my 2+ yr old iPhone 3GS with a brand new unit
I have the same problem with my 3GS that otherwise is in great condition. I replaced the battery with a new one and now it is even worse. It used to go dead at about 30% of battery life. It now dies at 60% of battery life. I am not one for conspiracy theories, but I believe Apple is systematically killing off older iPhones on purpose with their OS versions to prompt us all to upgrade. On the bus and train I ride in San Francisco it is almost impossible to spot a 3GS. This seems impossible given many of these are less that 2 years old. I couldn't be the only person on my route to work attempting to hold out for the iPhone 5 with what used to be a perfectly good phone (the 3GS). It seems clear that they are being killed off.
I say this as an Apple fan with a 27 inch iMac editing station, a Mac Book Pro and and iPad and a whole I run that I have ordered Apple products for. There simply is no other explanation as to why a 3GS is dying without even a shutdown sequence with a brand new battery. It seems quite suspicious that in the post right above this one, they quietly just gave Brett C a new iPhone.
Apple - if you are listening - to keep me buying of thousands of dollars worth of Apple equipment for my department each year you can stealthfully eliminate this post and give me an iPhone that works too. I won't tell.
Apple - you've come full circle. 1984 indeed.
I had the same problems, did everything, nothing worked. Finally took it to the apple store in Sydney, they plugged my phone in to one of their computers and it showed 700 plus charge cycles. The guy said that the most he'd seen was 400 and that usually iPhones start loosing charge at around 350.
Anyway I paid the 89 dollars it cost to replace the battery and figured it'll be a week. Before I get my phone back but the guy just wiped all the data off my phone and then goes "the way this works is that for the 89 dollars you get a new 3GS unit". All I said was "ohh" and walked out with a new 3GS. Which I have had for a month and it works just fine!
I don't know if they gave me a new unit because it had so many charge cycles or if that is what they do in the first place. I wasn't in warranty either. But if they are going to give out a brand new unit I suggest going to the apple store and just getting the replacement done there. The initial appointment with a genius bar doesn't cost anything and if they say something else then you can just go home but at least you would know what the problem is! I'm using ios5 and no problems so far.