rMBP - leave plugged in for all day use?

Discussion in 'MacBook Pro' started by 617arg, Apr 11, 2014.

  1. 617arg macrumors 6502

    Mar 3, 2008
    I recently purchased a 2013 rMBP with the intention of using it from time to time all day. My question is - do I leave it plugged in if I know it'll be a long day (8-10 hours), or use battery life and only plug in to charge?

    I know that I basically killed two batteries in my previous 2008 MBP by doing this, and learned to remove the battery if I was going to remain seated at one location for a long time. This is obviously not an option with the new models.

    Thanks for any advice
  2. maflynn Moderator


    Staff Member

    May 3, 2009
    I leave my plugged in frequently, though it gets unplugged about once a month (or there abouts)
  3. dmccloud macrumors 6502a


    Sep 7, 2009
    Anchorage, AK
    As long as you unplug the laptop about once or twice a month and let it run through a charge/discharge cycle, you should be fine.
  4. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    Just use the laptop as you normally would.

    I normally calibrate my battery per month.

    Under normal usage, I charge to full, disconnect it if I'm taking my laptop with me (which is practically daily), and then use it normally until the low battery warning comes up. I only leave it plugged in all day on Saturdays and Sundays (at night I shut down the Mac and disconnect the charger).

    My battery's gone through 88 cycles and still holds 99.8% of its charge (checked via coconutbattery).
  5. 617arg thread starter macrumors 6502

    Mar 3, 2008
  6. .Logan macrumors member

    Aug 7, 2010
    Houston, Texas
    Theoretically, by leaving it plugged in more often, therefore decreasing the number of cycles the battery goes through - would it then prolong battery life?

    If the laptop is plugged in, does the laptop use the AC power OR does it still use battery power which is just immediately replenished from AC power? (always wondered this).
  7. snaky69 macrumors 603

    Mar 14, 2008
    For your first question, Apple uses Li-Po batteries. Here's a few myths about batteries that need to die.

    Today's batteries do not have a memory effet.
    Today's batteries do not need to be constantly cycled to stay effective.
    Today's batteries cannot overcharge.
    Today's batteries all have a micro-controller ensuring proper charge rate, and that controller even trickle charges and discharges the battery to keep the electrons flowing when plugged in for long periods (we're talking months here).

    To keep it short and simple: Use your battery however you please, nothing you do will make it have a longer lifetime, it'll die on its own, regardless of your usage in 3-5 years.

    As for your second question, the computer will draw power from the AC only, unless its power needs exceed those the charger can provide. If that happens, it'll draw power from both the AC and the battery.
  8. 827538 macrumors 65816

    Jul 3, 2013
    Very well put, I done a project at uni regarding Li-Ion and Li-Po. I keep mine charged in for long periods while gaming and have no problems. Todays batteries use better chemistries and have much better control systems for charging and discharging. Definitely don't keep it at 100% indefinitely but so long as now and again you let it discharge to 20% and then backup you'll be fine. The only thing to be careful of with Li-Ion/Po is not to let them completely discharge (although most of the time the control circuits shutdown the system before that actually happens) otherwise they get wrecked after repeated total discharge cycles. Li-Ion unlike older battery tech which does have a memory effect, Li-Ion cells actually work best when they are routinely topped up, like going from 100% to 20-40% then back up. Just avoid total discharging and you'll be fine.

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