Battery life on Macbook Air 2015

Discussion in 'MacBook Air' started by MacBoook160, Jul 11, 2015.

  1. MacBoook160 macrumors 6502

    Feb 9, 2011
    I received the refurbished Air a few days ago, and it really is a beauty. Because of all the comments here, transferring files from my old MBP via Time Machine was a snap, and other than figuring out how Yosemite works, it's been a dream. My biggest challenge has been trying to decide upon a light but very protective case/sleeve for it, given the plethora of choices out there.

    Yesterday, I took it off power and started using it. Chrome was open, but because there was no wifi, I wasn't using it, a little bit of book reading via Preview and about 20 minutes of classwork through a downloaded quicktime mpeg4. The battery was dropping faster than I thought, but altogether, this was an hour max.

    I came back home and decided to see how the battery worked on regular tasks, so it was just internet browsing and Preview. No Quicktime, no iTunes, home wifi. In five hours, the battery went from 100-14 percent, which I found surprising.

    I called up Apple and he suggested that I always stay on battery life, let it cycle down, not leave it on AC power when it's fully charged; also helped me set up an appt at the Genius Bar for tomorrow (which sadly means I'll be carrying my unprotected laptop with me all day! I'll be swaddling it in a towel!)

    I know the answer is to see what the Genius Bar says, and of course, they'll fix whatever's wrong, but I'd love to hear any thoughts you might have. Am I overthinking it? Is this typical?

    And because I can't say it enough, what a pretty, pretty machine!
  2. motrek macrumors 68020

    Sep 14, 2012
    I don't know who you talked to at Apple but the guy is an idiot. You might suggest that he read Apple's own web pages and documents about how to care for a MacBook battery.

    1) Letting the battery run down is not necessarily good for it. It's arguably bad for it.

    2) Of course you can leave it on AC power when it's fully charged. The battery will stop charging when it's full, or nearly full, so there's no difference between leaving it plugged in and unplugging it.

    My guess is that the laptop is probably working fine and if the battery life was less than expected, in one case, then that might have been a one-off issue. Maybe the Spotlight index was being rebuilt or something.

    You should use the laptop for a few weeks and see what kind of battery life you get over that amount of time. Just use the laptop as you normally would and don't worry about doing things to "test" the battery.
  3. MacBoook160 thread starter macrumors 6502

    Feb 9, 2011
    Thanks, motrek! I gently suggested that I had read elsewhere that it's ok to work on AC power, and leave it fully charged all the time, but he (nicely, let me add) told me I was mistaken.

    Maybe I'll wait a bit before taking it in. Right now, it's at 55 percent at just over 3 hours of being off power. I won't be using it much next week, so perhaps I'll wait until after I'm back before I try testing it again.

    As always, thank you.
  4. motrek macrumors 68020

    Sep 14, 2012
    No problem. Another thing you can do is run Activity Monitor and look at the Energy tab and see what OS X thinks is using your power.

    The CPU tab might give you some information about a piece of software using an unexpected amount of CPU power too.

    Also, be aware that if you have the screen brightness turned up, that will cut into your battery power too and you will get somewhat less than what Apple advertises. I assume they do their testing with the brightness set to medium?
  5. MacBoook160 thread starter macrumors 6502

    Feb 9, 2011
    Great point. Today, with the computer being on (off AC power), though not being used the entire time, it went down to 12% in 7.5 hours. I think that's reasonable. The brightness is about halfway. I also think I have to give up my use of Chrome, especially as I'm admittedly a multiple tab addict. In the old machine, Chrome would crash daily. It works so smoothly and fast now, that I think I'm forgetting what an energy hog it is.

    It certainly charges back fast; last night, from 14% to 100 in 90 minutes.

    Also, it took me almost 5 hours to back up the MBP to Time Machine but only an hour to copy it onto the new MBA. Wow.
  6. motrek macrumors 68020

    Sep 14, 2012
    Glad you are enjoying your new MBA. I still appreciate my "new" 2014 model.

    Conventional wisdom is that Chrome is a battery hog. I keep fairly close watch on it by running a program called smcFanControl which displays the fan speed and system temperature in the top right corner, on the menu bar.

    Once in a while, the temperature is higher than it should be. Like, I'm not really doing anything with my computer but it's 65C instead of ~45C. Then I know something has likely gone wrong with one of my tabs in Chrome. I use Chrome's Task Manager to figure out which tab it is. Usually the misbehaving tab is showing a poorly-coded ad that is sucking up processor power. I either kill the page or refresh it, which almost always eliminates the problem.

    Doing this, I can get pretty good battery life, although I don't have exact numbers for you. But I admit that it's a lot of effort that shouldn't have to happen.

    I have tried switching to Safari and I didn't like the UI nearly as much as Chrome's.
  7. SSD-GUY macrumors 6502a

    Sep 20, 2012
    London, UK
    Erm, Apple states that it isn't good to let your battery always be plugged in. Check their battery life pages.
  8. motrek macrumors 68020

    Sep 14, 2012
    Link? This is all I can find currently and it doesn't say anything about plugging in vs. not:

    What would be the technical rationale for not leaving it plugged in BTW?
  9. maliu macrumors 6502a

    Jun 24, 2010
    Batteries need to be "exercised" a laptop used only plugged in will kill the battery faster. That said, just run it on battery occasionally to keep the battery healthy. I could find the Apple link to support it, but I'm lazy. :)
  10. verpeiler macrumors 6502a


    May 11, 2013
    Munich, Germany
    Always use your battery (ofc unless you do some cpu-intensive work). The only thing that's not good is to run it down to 0% every time.. but the batteries nowadays "like" to be used. You can test that by using something like Coconut Battery, you can even log your battery life.
  11. motrek macrumors 68020

    Sep 14, 2012
    No, no, no, no, no. Absolute nonsense.

    Running your laptop on battery power is a guaranteed way to wear out the battery.

    Why do you think Apple advertises that their batteries last a certain number of cycles? They don't say that their batteries can survive a certain number of hours of being plugged in. That should be a hint.

    Just keep your laptop plugged in whenever it's convenient, including when you're using it. This will minimize the wear on the battery and maximize its longevity.

    Batteries do not "like" to be "exercised." They are not dogs.

    Oh, by the way, I keep all of my devices plugged in almost all the time and their batteries are in excellent condition. My last laptop was a 2010 MBA that I sold after 4 years and it had over 90% of its original charge capacity remaining. My current laptop is a 2014 MBA that's 1.1 years old and the battery only has 46 charge cycles on it and its capacity is 99% of the original factory capacity.

    According to a lot of people, my batteries should all be ruined because I keep my devices plugged in almost all the time, but exactly the opposite has happened.
  12. verpeiler, Jul 15, 2015
    Last edited: Jul 15, 2015

    verpeiler macrumors 6502a


    May 11, 2013
    Munich, Germany
    No, no, no.. absolute nonsense.. ;-) Nice reasoning there

    I had my macbook plugged a long time and battery health went under 90% after 2 years... after using the battery regularly (down to ~15%) health went back up to 92/93% at over 300 cycles. Maybe you just don't see the correct health because you never use your battery.

    But hey, do whatever you think is best; I like to use my macbook as a portable device, I don't see the point of having it plugged all the time anyway. Sitting on my couch with a plugged laptop seems quite silly ;-)
  13. motrek macrumors 68020

    Sep 14, 2012
    First, those capacity percentages are just estimates. A change of a few percent when doing something-or-another is irrelevant. You might as well think that you caused it to rain on a particular day because you used your laptop on battery power.

    And you're almost proving my point if you had your laptop plugged in for 2 years and it still had 90% charge capacity. Batteries lose capacity over time due to nanocrystal formation on the cathodes and anodes. So losing a few percent capacity per year is expected and unrelated to having your laptop plugged in or not. If anything, your experience shows that leaving it plugged in is not bad for it.

    Of course it's a portable device and you're free to use YOUR device however YOU see fit.

    The problem is when you get on a message board and tell people that it's somehow good to put wear on their batteries. This misinformation gets perpetuated and then you get misinformed people all over the world going out of their way to wear out their batteries in a misguided attempt to preserve their longevity.

    That's really bad.
  14. feflower, Jul 15, 2015
    Last edited: Jul 15, 2015

    feflower macrumors regular

    Jun 25, 2009
    I don't know if this is true for everyone, or if batteries have developed since then, but:

    My 2009 MBP had an "enlarged battery" due to its being plugged in almost all the time.
    My friend's laptop also suffered from this.

    One day my trackpad couldn't be depressed, and I took it in to an Apple Store to get it checked out.
    They told me it was due to a enlarged battery, and replaced it for me (had Apple Care).

    Hmmmm...there are a few articles out there regarding this....
  15. motrek macrumors 68020

    Sep 14, 2012
    Unfortunately the problem is that up until recently (2005 to 2010 depending on manufacturer), the hardware and software for charging laptop batteries was stupid.

    It would blast the battery with max current up until the factory-specified capacity and then "trickle charge" the battery with a small amount of current continuously after that.

    This was HORRIBLE for batteries. Basically it was guaranteed to overcharge them, which quickly ruins lithium ion batteries. Remember when conventional wisdom was that laptop batteries would only last 1-2 years before they wouldn't hold a charge anymore? That's why. It really was harmful to keep your laptop plugged in and it definitely could cause the expanding battery problem you mentioned.

    But, times have changed. Modern Apple laptops keep track of the actual charge capacity of a battery (and not just the manufacturer-specified capacity) and don't charge it beyond that. They back off the charge current as the battery starts to get full. And they don't do this "trickle charge" nonsense anymore. If the battery is over ~95% full, it simply doesn't charge at all. It's like having the laptop unplug itself automatically from the wall.

    So unfortunately many people are stuck with conventional wisdom from the early 2000s about how you shouldn't leave your laptop plugged in and how it's somehow good to run on battery power.

    This conventional wisdom is completely outdated and wrong though.

    As for your 2009 enlarged battery issue, I doubt it was from leaving your laptop plugged in. That can be caused by other things, usually thermal expansion and contraction of the li-ion cells. If you exposed your laptop to rapid temperature changes, that probably caused the enlarged battery, more likely than overcharging.
  16. MacBoook160 thread starter macrumors 6502

    Feb 9, 2011
  17. motrek macrumors 68020

    Sep 14, 2012
    Sure. There's no reason to believe what I say since I'm an anonymous internet poster and you don't know my credentials etc.

    There's also no reason to believe the "geniuses" who work at Apple Stores, or even Apple certified technicians or Apple tech support either. These positions are for people with minimal engineering or technical qualifications. The technicians may be very good at disassembling and reassembling Macs but that requires no understanding of the underlying technology.

    So who should you trust? Well, straight from the horse's mouth on an Apple web site (with all the associated legal implications):

    In other words, be very careful about the temperatures that the computer and battery are exposed to, and follow certain best practices if you are going to store the computer unused long-term.

    But notice that certain "advice" is conspicuously absent: the page doesn't say anything about not leaving your laptop plugged in, or only using it on battery power, or regularly discharging the battery, etc.
  18. MacBoook160 thread starter macrumors 6502

    Feb 9, 2011
  19. Manzana macrumors 6502a


    Jul 19, 2004
    Orange County, CA
    What size Air 11 or 13?
    Don't run Chrome if you want long battery life. Screen brightness should be 25% to get most out of your battery.
  20. MacBoook160 thread starter macrumors 6502

    Feb 9, 2011
    11 inch. And I'm trying to wean myself off Chrome - you (along with motrek and a number of others) have offered me enough reason to do so, but I've been lax ;-)

    And my aging eyes can't handle 25% for too long!
  21. motrek macrumors 68020

    Sep 14, 2012
    I think 0% uses less power.
  22. motrek macrumors 68020

    Sep 14, 2012
    BTW -- I use Chrome myself. I like the UI more than Safari's.
  23. azurehi macrumors regular


    Jan 16, 2009
    From what I understand about an "upgrade" in Applecare, if the battery cannot maintain 80% charge it will be replaced free - is this correct?
  24. motrek macrumors 68020

    Sep 14, 2012
    If the MacBook is under warranty (regular warranty or AppleCare, i.e., extended warranty) then I believe Apple will replace the battery if it has both less than 1000 cycles and less than 80% of its factory specified battery capacity.
  25. robeddie Suspended


    Jul 21, 2003
    Of course it would, but then you're wearing out your eyes (trying to see the screen) rather than the battery. I paid $1500 for my macbook air, to enjoy it ... I want to have my screen brightness at a reasonable level, which is usually 75% or more.
    If the only way to get decent battery life was to turn down the screen so much that it's like looking through a screen door on a cloudy day, then that would be horse...t

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