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Q: Clarification regarding fully discharging a Macbook Pro built-in battery

As clearly stated in this support article:

 

Portables with built-in batteries:

Current Apple portable computer batteries are pre-calibrated and do not require the calibration procedure outline in this article.

 

Apple, however, also states:

 

Apple recommends charging and discharging its battery at least once per month.

 

 

Deeply discharging the battery is destructive. Furthermore it's clear that Notebooks with built in batteries do not require calibration. So, why is the same practice recommended when it 1) serves no functional purpose and 2) is harmful to your battery? Can someone provide clarification/insight regarding this inconsistency? (Looking at you, Plotinus Veritas )

 

Thank you in advance. 

MACBOOK PRO (RETINA, 15-INCH, LATE 2013), OS X Mavericks (10.9)

Posted on May 30, 2014 10:06 AM

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Q: Clarification regarding fully discharging a Macbook Pro built-in battery

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  • by Melophage,

    Melophage Melophage May 30, 2014 11:56 AM in response to nbar
    Level 5 (7,161 points)
    May 30, 2014 11:56 AM in response to nbar

    nbar,

     

    I took that to mean to do the (at least) monthly discharge down to 20% rather than to single digit percentages.

  • by nbar,

    nbar nbar May 30, 2014 12:06 PM in response to Melophage
    Level 5 (6,980 points)
    May 30, 2014 12:06 PM in response to Melophage

    Thanks for the reply. Which part? Apple's support article implies a full discharge once a month, IMO. i could be reading out of context, but I feel as though they would specify if they meant otherwise: IE "Apple recommends a discharge down to, but not below, 20% once a month. 

     

    Message was edited by: nbar

  • by Melophage,

    Melophage Melophage May 30, 2014 12:28 PM in response to nbar
    Level 5 (7,161 points)
    May 30, 2014 12:28 PM in response to nbar

    nbar,

     

    the second part — as maintenance rather than as calibration. It could well be that I misinterpreted their intent, but my misinterpretation has been working well for me so far.

  • by nbar,

    nbar nbar May 30, 2014 1:09 PM in response to Melophage
    Level 5 (6,980 points)
    May 30, 2014 1:09 PM in response to Melophage

    Yes, we're on the same page. I maintain my battery as you do. I avoid letting it dip below %20 (deep discharge). Bottom line: to completely discharge your battery monthly is harmful.

  • by OGELTHORPE,

    OGELTHORPE OGELTHORPE May 30, 2014 1:10 PM in response to nbar
    Level 9 (52,108 points)
    Mac OS X
    May 30, 2014 1:10 PM in response to nbar

    nbar wrote:

     

    Apple's support article implies a full discharge once a month, IMO. i could be reading out of context, but I feel as though they would specify if they meant otherwise: IE "Apple recommends a discharge down to, but not below, 20% once a month. 

     

    In that portion, no percentages are explicitly given and I do understand that it could be interpreted as a full discharge.  That though would be wrong.  I use the information available in Battery University as my guide where the author indicates that total discharges have a negative impact on battery life.

     

    In principle I agree with Melophage though I usually tell the OP to discharge to the 40% level prior to recharging the MBP. 

     

    Ciao.

  • by Network 23,Helpful

    Network 23 Network 23 May 30, 2014 2:06 PM in response to nbar
    Level 6 (12,043 points)
    Mac OS X
    May 30, 2014 2:06 PM in response to nbar

    nbar wrote:

     

    Apple, however, also states:

    Apple recommends charging and discharging its battery at least once per month.

    My assumption is that was written by Apple before the non-removable batteries, and has not been updated for whatever reason. I believe that for unibody MBPs, the more recent advice of deep discharge calibration being unnecessary is intended to be the current advice.

  • by davfranco,

    davfranco davfranco Aug 31, 2014 2:35 PM in response to nbar
    Level 1 (0 points)
    Aug 31, 2014 2:35 PM in response to nbar

    This truly *****, before, Apple used to recommend power cycling devices, so I think many of us still had that same misconception for newer Apple devices.

     

    I own the latest MBP Retina 13', and I don't use the battery that much. Not knowing about the switch in advice my battery unintentionally drained two different times (5-6 hrs followed before I recharged), and I've noticed inconsistent performance, meaning remaining time varies widely, even if I'm only browsing.

     

    I downloaded the Battery Health App and it shows 17 cycles in 9.2 months, 99% health, with current max 6284mAh, out of original max of 6330mAh. Numbers seems fine, so I can't understand the change. Same numbers on the system report.

     

    Is there a possibility for the battery being damaged on those two occasions, all tho numbers say contrary? MBP's still under warranty, but I guess the techs at the Genius Bar will say the battery is good.

     

    I'd like to hear on thoughts on it... thanks!

  • by Network 23,

    Network 23 Network 23 Aug 31, 2014 5:18 PM in response to davfranco
    Level 6 (12,043 points)
    Mac OS X
    Aug 31, 2014 5:18 PM in response to davfranco

    davfranco wrote:

     

    Is there a possibility for the battery being damaged on those two occasions, all tho numbers say contrary? MBP's still under warranty, but I guess the techs at the Genius Bar will say the battery is good.

     

    I'd like to hear on thoughts on it... thanks!

    I don't know why you're seeing strange performance, but my opinion is that two full discharges should not permanently damage the battery. I think it would have to go through a lot more than that before negative effects would happen. But I don't work for Apple so I don't know for sure.

     

    There is such a thing as over-discharging Li-ion batteries, but a consumer has to work pretty hard to get it to happen, and when it does happen the battery can't be used. That clearly isn't happening here. Like all companies that use Li-ion batteries, Apple has a protection circuit that watches in case voltage drops to a certain cutoff threshold and if you hit that, it shuts off the hardware before the battery is really truly drained. The following article might be helpful; the section in it that applies to this is "Over-discharging Lithium-ion" so you can scroll down to that.

    Charging Lithium-ion

     

    At only 17 cycles over 9 months, I am not sure if the power manager in OS X has enough usage data to accurately predict remaining charge. I wonder if the battery estimates will smooth out over time. Most users go through maybe 100-200 cycles a year.

  • by nbar,

    nbar nbar Aug 31, 2014 7:10 PM in response to Network 23
    Level 5 (6,980 points)
    Aug 31, 2014 7:10 PM in response to Network 23

    Agreed. Two full deep discharges shouldn't permanently damage the battery. It's making a habit of it that causes the permanent damage. Also, the damage isn't necessary overt [ie: Replace battery now notification], it's misusing the battery consistently to the point where you've severely shortened the lifespan such that it doesn't come anywhere near hitting Apple's "80% FCC after 1000 cycles" specifications for built in batteries.

     

     

    Apple has a protection circuit that watches in case voltage drops to a certain cutoff threshold and if you hit that, it shuts off the hardware before the battery is really truly drained.

     

     

    This same firmware protection is implemented across Apple devices. It's the reason why you're able to see this graphic appear on a "completely drained" iOS device:

    iphone-low-battery-300x227.png

     

    ...which obviously wouldn't be able to do so without a bit of juice.

  • by paolaEdi,

    paolaEdi paolaEdi Sep 1, 2014 9:34 AM in response to nbar
    Level 1 (14 points)
    Mac OS X
    Sep 1, 2014 9:34 AM in response to nbar

    sorry guys, so how do you manage your battery exactly? Doesn't keeping the laptop constantly on power also damage the battery? I work on my 13" MBP with retina display constantly.

  • by Network 23,

    Network 23 Network 23 Sep 1, 2014 12:27 PM in response to paolaEdi
    Level 6 (12,043 points)
    Mac OS X
    Sep 1, 2014 12:27 PM in response to paolaEdi

    paolaEdi wrote:

     

    Doesn't keeping the laptop constantly on power also damage the battery?

    It isn't the worst thing you can do. The worst thing you can do is empty the battery to 0 every day. Keeping the laptop on AC power is not great, but as long as you use it on battery every few days it will probably be OK. There can be increased battery deterioration if the laptop is plugged in, the battery is at 100%, and the battery is exposed to high temperature, see Table 3 in How to Prolong Lithium-based Batteries. Table 2 explains why deep discharges should be avoided.

     

    Generally, the laptop battery is designed to last longest if it is sometimes plugged in and sometimes unplugged, and when unplugged it is discharged usually to more than 50% before being plugged in again. If you leave it plugged in a lot, maybe set a calendar reminder to use it on battery for a while, every few days.

     

    My MacBook Pro is plugged in most of the day, and used on battery about 2 hours a day. My battery is 2.5 years old and using the practices above, still reads 95% of original capacity after over 400 cycles.

     

    You will never prevent a Li-ion battery from deteriorating because it is going to lose charge capacity over time even if it is never used. All you can do is slow it down.

  • by paolaEdi,

    paolaEdi paolaEdi Sep 1, 2014 1:13 PM in response to Network 23
    Level 1 (14 points)
    Mac OS X
    Sep 1, 2014 1:13 PM in response to Network 23

    Many thanks Network23 - currently (but I've only had my MBP for a couple of months) I work on battery, then charge it when it reaches about 20% (though sometimes I do not notice and goes lower), then plug it in up to 100%, then disconnect until it goes to 20%, and so on. I work from home a lot, and in a full day it can go through almost two full charges (from 20).

     

    I think I should get used to switching it off at night.

     

    Also, I am planning to use it remotely when commuting to/from work by connecting my iPad with parallels - but in that case I'll have to leave it plugged in, otherwise it will not wake up, but from what you say this should not be a big issue then. Still wonder whether a closed lid may result in overheating that may damage the battery?

     

    Thanks for your help!

  • by Network 23,

    Network 23 Network 23 Sep 1, 2014 1:46 PM in response to paolaEdi
    Level 6 (12,043 points)
    Mac OS X
    Sep 1, 2014 1:46 PM in response to paolaEdi

    paolaEdi wrote:

     

    Many thanks Network23 - currently (but I've only had my MBP for a couple of months) I work on battery, then charge it when it reaches about 20% (though sometimes I do not notice and goes lower), then plug it in up to 100%, then disconnect until it goes to 20%, and so on. I work from home a lot, and in a full day it can go through almost two full charges (from 20).

    If that's what you have to do to get your work done, that's fine. If you had a choice I'd say plug it in at a somewhat higher percentage, but if that isn't practical then some additional battery deterioration may simply be a cost of doing business, like if you have to spend more on gasoline for a company car. Changing at 40 or 50% may be better than 20%, but 20% is still better than going to zero.

    paolaEdi wrote:

     

     

    I think I should get used to switching it off at night.

    I just sleep mine because in the morning I like to pick up where I left off. I dislike having to reopen a bunch of apps and documents.

    paolaEdi wrote:

     

    Also, I am planning to use it remotely when commuting to/from work by connecting my iPad with parallels - but in that case I'll have to leave it plugged in, otherwise it will not wake up, but from what you say this should not be a big issue then. Still wonder whether a closed lid may result in overheating that may damage the battery?

    It can depend on how you set it up. There are still ventilation slots that don't involve the keyboard, but I think leaving the lid open does help a little. If it's closed on an uncluttered desktop it might be OK. What is a problem sometimes are people who slide the closed laptop into a shelf or home theater cabinet with not a lot of room around it and over it, the restricted ventilation can encourage overheating.

     

    If I was going to leave it on a desk running at home and I was concerned, I might decide to point a low-speed household fan at it. One of my old PowerBook laptops would get hot and pointing a small fan at it made a big difference.

  • by paolaEdi,

    paolaEdi paolaEdi Sep 2, 2014 12:03 AM in response to Network 23
    Level 1 (14 points)
    Mac OS X
    Sep 2, 2014 12:03 AM in response to Network 23

    If that's what you have to do to get your work done, that's fine. If you had a choice I'd say plug it in at a somewhat higher percentage, but if that isn't practical then some additional battery deterioration may simply be a cost of doing business, like if you have to spend more on gasoline for a company car. Changing at 40 or 50% may be better than 20%, but 20% is still better than going to zero.

    It is actually due to my previous wrong conviction that it had to go down to 20% - I'll change it to 40% then, will be careful.

     

    Thank you for your detailed answer!

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