iPhone 3G Battery Jumps up ~20% once plugged in

Discussion in 'iPhone Tips, Help and Troubleshooting' started by sekelly, Jul 28, 2008.

  1. sekelly macrumors newbie

    Jul 14, 2008
    Hey all,

    I searched around the forums to see if I could find a thread that touches on this but I was unable to come across one. If someone knows of a thread that offers some kind of explanation please point me there and we can go ahead and ignore this one.

    Often, when I plug my iPhone 3G 8 GB model into a USB slot on my Macbook, it immediately jumps up approximately 15-20%. For example, today I had it at approximately 10% (just got the 10% warning), plugged it in, and it was around 25-30% immediately after recognizing that it was plugged in.

    I'm pondering a couple of questions about this...

    Does this mean the charge that it had when I plugged it in was actually 15% less than was actually existing in the battery? Or does this mean that the phone/battery thinks it has been charged 15% instantaneously? Either way I am not getting the most out of the battery...

    Perhaps it simply indicates the wrong charge, but will charge itself to full (actual full, not implied by the iPhone OS) regardless of the indication on the screen?

    Anyways any input or experience would be appreciated. This is the second issue I've had, and apart from these experiences I love the product.

  2. bigmouth macrumors 6502

    Jul 24, 2008
    Your battery meter just needs a few deep charges to calibrate. Let it run all the way down (i.e., until the phone shuts off) then charge it fully. After a few charges, it should register more accurately.
  3. MBHockey macrumors 68040


    Oct 4, 2003
    New York
    I experiences this for a whole year on my 1st gen iPhone...i wouldn't worry about it. My battery was awesome on that phone.
  4. sekelly thread starter macrumors newbie

    Jul 14, 2008
    Ok, thanks for the responses.

    I did about 5 or 6 full battery cycles. This is where I used iPhone until it powered itself off, and then recharged to full. Rinse and repeat.

    That makes me feel a bit better. I just don't want to be losing battery, as I have a pretty high everyday usage.

    Thanks again.
  5. DamnDJ macrumors regular


    Feb 17, 2003
    Denver, CO
    Do NOT let your battery run all the way down to 0. This can hurt the battery and shorten its life. Try not to let it go below 20% before recharging it.

  6. ucbearcats macrumors member

    Jul 20, 2008
    Cincinnati, Ohio
    Not true, the iPhone automatically shuts off before you can even drain your battery to 0%. You are fine to let it die the recharge.
  7. i-John macrumors 6502a


    Jul 14, 2008
    The Republic of Texas
    The reason is that the lithium based batteries are designed to fast charge to about 80%, then trickle charge the rest of the way.

    It's also good about once a month or so, charge it to 100% then let it drain all the way. It keeps the electrons in the battery moving and preserves battery life.

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