Does keeping it plugged in all the time reduce battery life?

Discussion in 'MacBook Air' started by GadgetGeek407, Mar 27, 2009.

  1. GadgetGeek407 macrumors 6502a

    Joined:
    Mar 26, 2009
    Location:
    florida
    #1
    I have heard both and figure good to clarify with those using it...if i keep it plugged in most all the time does that reduce my battery life? some people i saw are getting 2.5 hours others 4+...ill really just being internet n AIM thats it...
     
  2. MistaBungle macrumors 6502a

    MistaBungle

    Joined:
    Apr 3, 2005
    #2
    Yes and no.

    Once the battery is charged, the battery is no longer used and the computer switches to AC power which will not shorten the battery life.

    However, not allowing your battery to cycle will be bad for your battery. This means leave it on, unplugged and let it run out. I prefer to just have iTunes playing with no other apps open.

    Plug it back in once it shuts itself off and you've just cycled your battery.

    Proper instructions can be found on Apple's page.
     
  3. Mactagonist macrumors 6502a

    Joined:
    Feb 5, 2008
    Location:
    NYC - Manhattan
    #3
    Just like all of us, as soon as it is made the battery is on a one way trip to death. With reduced capacity along the way as it gets older and older.

    In a perfect world laptop batteries would be stored in a cool place at 40% charge, and then installed, fully charged and used only when needed. In the real world that kind of usage model is impossible. Thus the charging circuitry and design of the battery is such that it will deliver as much life as possible in normal use. So just use it and dont worry about it, when it dies buy another one.
     
  4. dubhe macrumors 65816

    dubhe

    Joined:
    May 1, 2007
    Location:
    Norwich, UK
    #4
    Good point made by Bryan, just use it and when it dies, replace it. Regardless of your usage pattern it should last several years.

    If however, you wanted a different answer, then I would recommend unplugging a couple of times a month and running it down to less than half before charging up again, just to keep the juices flowing!

    Conditioning your battery (running it until flat then charging fully) is a little false, it conditions the chip inside that tells your computer how the battery is performing, not the actual battery. All conditioning does is make the "hours remaining on battery" more accurate. The battery will last as long as it wants to.
     
  5. McGilli macrumors 6502

    Joined:
    Nov 11, 2008
    #5
    Just a note - for the last 2 months or so - I have had mine plugged into the power cord almost the entire time - no big deal. what is interesting - is that every time that i wake it from sleep - the battery meter has different readings. (i use it every 3 days or so right now)

    one day it is 100, then 92, then 97, then 99 etc etc.....

    always plugged into the ac power. did the whole re-calibrate one day - but seems to make no difference - i find that if i power it down though - as opposed to sleep (like i do 99% of the time) - once restarted the meter reads 100 again every time.
     
  6. brop52 macrumors 68000

    brop52

    Joined:
    Feb 26, 2007
    Location:
    Michigan
    #6
    It varies between 95-100 because it stops charging at 100% and begins again around 95%.

    As for the correct way to use it, they recommend about 2-3 cycles per week and calibrating fully every 2-3 months. This includes charging fully and leaving charged for two hours, discharging fully and leaving discharged for five hours, and then charging fully.
     
  7. dubhe macrumors 65816

    dubhe

    Joined:
    May 1, 2007
    Location:
    Norwich, UK
    #7
    2-3 cycles is a lot, a cycle is a full discharge (or two half discharges, or four quarter discharges...) that means you need to spend around 10 hours a week running on battery, and your battery will start to show a significant drop in performance after 18-24 months.

    I think the OP is more interested in preservation of his battery, for that I would recommend 2-3 cycles a month.
     
  8. sparkie7 macrumors 68000

    sparkie7

    Joined:
    Oct 17, 2008
    #8
    yeah, just like us humans LOL :D:D
     
  9. brop52 macrumors 68000

    brop52

    Joined:
    Feb 26, 2007
    Location:
    Michigan
    #9
    I know what a cycle is. I'm just talking about the normal use and what the limit should be. I'm on my computer a majority of the day and I'm a medical student who watches a lot of lectures. Obviously I still keep it plugged in most of the time while in use when I can. Keep in mind that someone who heavily uses the computer is slowly discharging even while plugged in between 100-95% and that overnight the battery does lose a significant percent of its charge while asleep.

    2-3 cycles a month is not that realistic for a heavy user unless they keep it plugged in all day long or don't use it that much. Lets say the battery loses 1% per hour of sleep and that it is not in use for 10 hours in this state. That's a 10% loss overnight. Then you use the computer all day long and it goes between 100% and 95% 3 times a day. That's a loss of 15% a day. 7 days of that equals 175%. So that's nearly two cycles with never using the battery at all and only unplugging overnight. So I'd say 2-3 cycles a week could be a pretty good guideline to keep to for someone who isn't keeping it charging overnight. How many cycles do you have on your battery and how long have you had it? My first battery was faulty on my machine and I have 28 cycles after 11.5 weeks on this second battery. That comes to 2.4 cycles a week. Apple rates its batteries to keep 80% of the charge for three years or 300 cycles. So if you use 3 cycles per week your battery should last you to 80% at two years and 2 cycles per week will last three years.

    If we want to expect someone to have it plugged in 24/7 while in use obviously it is best to just calibrate fully every month and leave it at that as a way to preserve battery. Like I said overnight sleeping is a significant source of discharging. The fact remains that there is no sure-fire way to keep batteries alive. Some of them just fail for no reason and if they do fail early it means a free battery. So barely using it may not be the best way to go. It is a notebook after all and is meant to be portable and even to places that don't have power. In the end, just use the battery how you see fit but don't go overboard.
     

Share This Page