iPhone 3GS - Powering Off "Too Early"

Apple iPhone - iPhone 3GS - Powering Off "Too Early"

I've had my iPhone since August 2008. In the last few weeks, it's been powering off anywhere from 20-45%. I'll be working on it, and it will just shut down. I will turn it back on, and it will go for about 20 seconds (long enough to see the battery level is still 1/5 or more) then shut down again.

This afternoon it shut down at 44%. I plugged it in, and it wouldn't turn on for at least ten minutes - when I pressed the Power button I got the horizontal battery with a sliver of red, and the lightning bolt icon under it. All the power connections were good.

Any thoughts? Is this the beginning of the end?

iPhone Battery
Although lithium ion batteries cannot be "reformed" as NiCad's could be by discharging them fully and re-charging them, the iPhone's *calibration* (accuracy of reading the level of charge) can be improved by this maneuver.

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Go find the article on calibrating the battery. Try it a couple of times, otherwise it may be time to replace the battery. You are "supposed" to calibrate it monthly, but I don't know a soul that does.

If you have used the phone for 2 years, it may be time, but if it is saying 40% then I think it just needs a calibration.

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How, pray, does one calibrate a battery and why? This is the first time I hear the of the need to do so.

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Agreed. I'm confused on the process of it. I've looked online, and I've seen everything to turning off Push and 3G to letting the battery run down completely (which obviously won't work since mine is dying at random levels).

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I believe that the iPhone battery is not the type that one let's run down completely. In fact every time you add power to it you are helping it.

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I'm sorry I was thinking of the article http://support.apple.com/kb/HT1490 for
portables, the closest I find for the iPhone is
http://support.apple.com/kb/TS2802.

Guess it is time to have the battery replaced.

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You're not calibrating the battery, but rather the gauge. An Li Ion battery loses capacity as it ages. The analogy is like your car's gas tanks shrinking with age. Since the phone's meter measures charge (coulombs) going in and out of your batter, if the capacity goes down the meter is incorrect. By draining the battery and fully recharging, you calibrate the 0% and 100% capacity points.

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I will give it a shot... but if the battery shows 35% and the phone conks out, obviously I can't let the battery run down to 0. That's what I'm trying to figure out...

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Actually, you are letting it run down to zero. The phone shuts off at a certain voltage. The meter needs to show 0% at that point, which is what you're calibrating.

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So... if I'm understanding you correctly... when my phone shuts off at whatever level (40%, 22% or 3%), I should then leave it off the charger for 8 hours or so, then recharge it completely?

Sorry for the confusion... just trying to clarify.