8 Replies Latest reply: Aug 25, 2007 12:25 PM by T.M.
Pritesh Mistry Level 1 Level 1 (0 points)
I have just purchased a new mac book pro and wen i charged up the laptop the battery icon only goes up to 99%. Its never been to 100%. I know that the batteries loose their life but not if they have not been used and not if the cycle count it only 3. At this rate i will not even get my 80% battery life on 300 cycle counts.

I'm kinda new to mac - well i have used them for many years at work (imacs), but never owned one and i just need to get up to speed on the maintenance and other little issues as such!!

Please help!!

MacBook Pro 15", Mac OS X (10.4.10)
  • Centurion1 Level 4 Level 4 (1,300 points)
    Hi there, this is from Apple

    Some PowerBook G4, iBook, MacBook Pro and MacBook computers may not show the battery as 100 percent charged in Mac OS X, even when the power adapter is plugged in. The battery appears to stop charging between 93 percent and 99 percent. (PowerPC-based computers may stop charging between 95 and 99 percent; Intel-based computers may stop charging between 93 and 99 percent.)

    This is normal. The batteries used in these computers are designed to avoid short discharge/charge cycles in order to prolong the overall life of the battery. Because of this, when setting the Mac OS X battery status menu bar icon to display charge state by percentage, you may notice that the reported charge stays between 93 or 95 percent and 99 percent. When the battery level eventually drops below 93 or 95 percent, it will charge all the way to 100 percent.
  • T.M. Level 1 Level 1 (35 points)
    I have a follow up question on this. I was searching for a problem of mine that is similar to this. I realize if the battery is in between the given upper ranges it will not charge to 100% to avoid over working the battery. BUT what if I start from a low charge, plug in my macbook pro, it charges to 100% THEN after a day of use while being plugged in the entire time the percentage drops to 99% even 98%? I am just concerned as to why my charge is dropping while the laptop has been charged to 100% and has not been unplugged, how/why is it discharging?

    Thanks,
    TM
  • infinite vortex Level 7 Level 7 (21,400 points)
    Be sure to do a Battery Calibration…

    http://docs.info.apple.com/article.html?artnum=86284

    … on your new battery.
  • JASimon Level 2 Level 2 (290 points)
    If you really crank the machine hard the power adapter may be unable to supply all the power needed by the computer. In those cases it can dip into the battery to supply the additional power.

    For example, I have noticed that after playing Civilization IV on AC the battery will go down maybe 50-100mAh.

    This is part of the reason why the processor is capped at 50% speed if you run it off AC with the battery out. It is possible for the power demands of the computer when running flat out to exceed the capabilities of the power supply (if only marginally).

    Read the Apple technical note for details.
  • Ricktoronto Level 6 Level 6 (11,550 points)
    The bottom line is a 99% battery that is new is a new battery and extrapolating to that it won't work after X uses is just bad math. Ignore it.
  • ElBiggus Level 2 Level 2 (365 points)
    After 78 cycles mine's at 97%, but even brand new out of the box it was only at 99% so I wouldn't worry unduly.
  • JASimon Level 2 Level 2 (290 points)
    To clarify - I am just talking about current charge not maximum charge or "health". I presume that is what TM was commenting on rather than the maximum charge that the OP was asking about.

    As far as "health" goes - yeah, what they said.
  • T.M. Level 1 Level 1 (35 points)
    Thank you for the technical document explaining the Macbook pro will tap into the battery for additional power when plugged in. Very interesting! That must be the cause with my oh so importantly intensive apps ha. Thank you, TM