Plugged in and using battery??

Discussion in 'MacBook Pro' started by vmachiel, Sep 13, 2011.

  1. vmachiel macrumors 68000

    Feb 15, 2011

    Weird thing was happening, my MBP charger was plugged in but it was still running on the battery. i removed the magsafe to find half the battery drained. Has anyone else ever have this?
  2. snaky69 macrumors 603

    Mar 14, 2008
    If you are very hard on the computer running very processor and graphics card intensive programs(some games can do this too), the power adapter is not able to provide all the power needed to the computer, and the computer will start draining the battery to compensate.

    You're seeing perfectly normal behaviour, nothing to worry about.
  3. dusk007 macrumors 68040


    Dec 5, 2009
    It uses the battery for power spikes but half empty is probably something else.
    Maybe it just didn't realize it was plugged in. Little bug or not properly adjusted who know. A restart or remove and attach would probably fix it.
  4. windowstomac macrumors regular

    Jun 23, 2011
    My MBP frequently reports being charged to 97-99% despite being plugged in all day, so perhaps a tiny amount of battery is being used....
  5. vmachiel thread starter macrumors 68000

    Feb 15, 2011
    Ok, thanks for the responses. Did a reboot and it's working fine again.
  6. snaky69 macrumors 603

    Mar 14, 2008
    The battery controller on the battery charges it to 100%, then lets it trickle down to 95% then back to 100%, it's how it keeps the battery healthy by giving it some exercise and is perfectly normal.


    If said spike is a huge Finite Element Analysis requiring all 4 cores maxed out + the GPU pitching in, said spike can last for a few hours.
  7. GGJstudios macrumors Westmere


    May 16, 2008
    It's possible that during periods of extreme demands on the system, it will draw power from both the AC and the battery. More likely, however, is that the MagSafe adapter wasn't fully connected the entire time, so it was only drawing on battery.
    That's not correct. In fact, they are designed to avoid such short discharges and charges.
    See the CHARGING section of the following link. This should answer most, if not all, of your battery questions:

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