Inaccurate battery indicator on your iPhone 3G?

Have you ever wondered about the accuracy of the battery indicator and the 20% and 10% warnings on your iPhone 3G? After a couple of months or in some cases after an iPhone OS update the battery indicator may need some re-calibration.

Re-calibration of the battery indicator on iPhone 3G

However, if you experience a strange behavior of the battery indicator e.g. 20% and 10% warnings coming very soon but operation sustains for a relatively long time afterwards, then you might consider re-calibrating your iPhone’s battery indicator manually.

This can be done in 3 easy steps. You won’t loose any data and this procedure will not destroy your battery though it will add another cycle to the counter (So does every regular charging cycle).

  1. Reset your iPhone by holding down the sleep/wake button and the Home button simultaneously until your iPhone resets. Ignore any pop-up messages and keep holding down both buttons until the screen turns black and the Apple logo appears. Now it’s ready to learn new values for the capacity of its battery.
  2. Discharge your iPhone until it turns off automatically. The battery has reached a minimum level and the iPhone won’t turn on again. It shows you an emtpy battery icon and indicates to recharge. You don’t have to force a full discharge, you can just use it as usual until it turns itself off. To deplete your battery faster turn on 3G, Wi-Fi, Bluetooth, GPS (Location Services) and turn up the brightness to max. Then run a video or just start Skype which is an excellent app to drain your battery quickly even without doing anything.
  3. Fully charge your iPhone. That’s it, just charge it to the max and your iPhone learned the lowest and highest capacity levels of its battery.

Now the battery indicator should show you an accurate level of its charge and decrease more linear during operation.

Should I be worried or bring my iPhone to service?

There’s nothing to worry about, this is a normal behavior for any device using rechargeable batteries as a power source. Most batteries have a limited life span and will lose some capacity over time. Especially the full capacity of a lithium type battery will decrease over time (after increasing a bit during the first couple of cycles) and should be replaced after 2-3 years. In most cases even older lithium batteries will allow you to operate your device but with a dramatically reduced operating time.

This is neither a new trick nor is it a hack. I found this in the Apple support forums a long time ago and just wanted to post this as a reminder. I just got a new iPhone 3G from Apple after the knob of the ring/silent switch came off from my old one. It was a bit loose and the guy in the Apple Store completely broke it off during inspection. He instantly gave me a new iPhone 3G and deleted all data from my old one. Then I went home, put the new iPhone into the dock and restored it from my last backup that morning. 1h later I had all my data back and all my apps running. I didn’t lose anything, even my call logs and text messages were back.

Operating time on my new iPhone 3G is still a bit weak (1 day with 3G/Wi-Fi/GPS on and moderate usage) but increasing after a few charging cycles. My old iPhone 3G did stand 3 (sometimes 4) days with 3G/Wi-Fi on and Bluetooth/GPS off when used sparsely.

Great service from Apple! Thanks.

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14 Responses to Calibrate battery indicator on iPhone 3G, 3GS, 4, 4S

  1. Jorge says:

    Is it OK to do this if I just got my iPhone 3 days ago?

  2. jERRy says:

    It won’t hurt your iPhone but gives you a better battery level reading. Do it now and repeat it in about a month or two.

  3. Jonathan says:

    i saw that also on the mac webby.hmm but i posted on forum.pple saying that by running it down, will damage the batt. and batt shld be charged as regulary as possible. any comments?

  4. jERRy says:

    True, you should charge your battery regularly. It’s also true that if you discharge a battery completely it’ll cause damage. That’s why devices shut down automatically when the battery reaches a critical level to prevent damage to the battery.

    Your iPhone/iPod shuts down before the battery is completely empty. That minimum level includes a small charge to sustain standby for a while. You can check that the clock continues running even if you left your iPhone empty over night. If you let it lie around for a couple of days more the clock will be reset and that’s an indication of a completely depleted battery. Try to avoid that situation though it won’t break your iPhone if it happens just once.

  5. Jonathan says:

    so is better to calibrate once a month or ?

  6. jERRy says:

    There is no schedule for this. Just do it when you suspect incorrect readings. After I got my replacement iPhone I had to do it twice in the first 2 weeks or so. Then after an update of the OS I usually have to do it once.

    FYI: I removed the double post. Comments have to be approved before they appear.

  7. Jonathan says:

    So sorry for the double post :).
    The need of the calibration is needed only when I suspect incorrect readings? If I do not suspect,isit wise to do so?

  8. jERRy says:

    If you’re unsure then do it every once in a while e.g. once a month. You’ll do it less frequently after a while as you’ll care less about it later on. It’s just a toy after all, though I’ve got to admit that it’s been my favorite toy/gadget/mobile device so far, even after more than a year ;-)

  9. @Me1ody_Ma1one Your battery indicator might need recalibrating I guess

  10. Jude says:

    Hey, my iPhone 2G battery always shows full. It’s not jailbroken either and it’s a factory unlocked one! I’ve kept music shuffle/repeat on and let the battery die. I did a 4 hour recharge after that but same issue. Could it be some battery issue as the 2G is now 5 years old? Please do help me out as I still love my 2G :) Thanks

    • jERRy says:

      Hey Jude, 5y is very old for a Li-battery. Usually they start losing capacity noticeably after 2-3y and should be replaced eventually. So does your iPhone die very quickly or is it just the indicator that bothers you?

  11. @avatastic says:

    @Be3G There are instructions on how to force a recalibration – – So I guess it doesn’t do it automagically.

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