Battery Charging quandary - Conflicting Opinions, Help!

Posted:
in Current Mac Hardware edited January 2014
Never, in my thirteen years of solid computer use, have I come across as strange a situation as I've apparently found today. The issue is the charging of Lithium Ion batteries, and, specifically, whether they should be deep discharged. Witness, now, two major computer corporations contradict each other on the issue:



Apple TIL:

Lithium-ion



Recharge Lithium-ion batteries when they become depleted. Although they are not subject to the memory effect, it is suggested that you let the battery drain fully before recharging.


(check the bottom of the page for quotation)



VS.



IBM Support



NOTE:

Do not deep-discharge Lithium Ion batteries. Batteries can degrade when they are left unused for long periods of time. For some rechargeable batteries (particularly Lithium Ion batteries), leaving a battery unused in a discharged state could increase the risk of a battery short circuit, which could shorten the life of the battery and can also pose a safety hazard. Do not let rechargeable Lithium-Ion batteries completely discharge or store these batteries in a discharged state.



Am I missing something important here, or did Apple totally contradict IBM on this issue? Now I normally would believe Apple, but the opinion provided by IBM is supported by other sources I looked at; Apple's clearly in the minority. So what's going on here?



I want to prolong the life of my iBook and my iPod. My iBook's battery is apparently going out on me, after almost three years of service. I used to not deep charge it, until I saw a noticeable memory effect (but now I realize it was likely just the PMU). So I'm resigned to the fact that I'm going to need to replace that, and at least I can. I wanted to confirm online that deep charging is the right thing to do, as I always thought it was. I also just started deep charging my iPod, and I'm now quite concerned because of everything I've read. (Recall, that in Apple's infinite wisdom, the iPod's battery isn't user accessible.) Yet, Apple seems to contradict all those opinions. So, again, what in the world is going on here?



And here's one last opinion, which casts deep charging in a poor light:



Battery University



Some lithium-ion batteries feature an ultra-low voltage cut-off that permanently disconnects the pack if a cell dips below 1.5V. A very deep discharge may cause the formation of copper shunt, which can lead to a partial or total electrical short. The same occurs if the cell is driven into negative polarity and is kept in that state for a while.



Manufacturers rate the lithium-ion battery at an 80% depth of discharge. Repeated full (100%) discharges would lower the specified cycle count. It is therefore recommended to charge lithium-ion more often rather than letting it down too low. Periodic full discharges are not needed because lithium-ion is not affected by memory.

Comments

  • Reply 1 of 7
    big macbig mac Posts: 480member
    Someone must have an answer.
  • Reply 2 of 7
    cubedudecubedude Posts: 1,556member
    Quote:

    Originally posted by Big Mac

    Apple's clearly in the minority.



    What else is new?
  • Reply 3 of 7
    eugeneeugene Posts: 8,254member
    Simple enough. By drain fully, Apple means let the battery drain to the point where it warns you it's about to shut itself off. I don't think they expect people to have a Li-Ion battery discharger/cycler/conditioner.



    I know for sure NiMH batteries should not be deep-discharged. I usually discharge my 1.2V NiMH AA, AAA, sub-C, etc. cells to .9V each for storage, so that 80% figure for Lithium-Ion cells quoted above is about right, I guess.
  • Reply 4 of 7
    big macbig mac Posts: 480member
    Thank you for the information, Eugene. So if we allow our batteries to discharage to sleep state, that won't adversely affect them? That's not really deep discharging? I read on one site that Lithium batteries should be recharged when the about fourty percent empty, and that they should be recharged often. That's obviously not what Apple's talking about.
  • Reply 5 of 7
    eugeneeugene Posts: 8,254member
    Quote:

    Originally posted by Big Mac

    Thank you for the information, Eugene. So if we allow our batteries to discharage to sleep state, that won't adversely affect them? That's not really deep discharging? I read on one site that Lithium batteries should be recharged when the about fourty percent empty, and that they should be recharged often. That's obviously not what Apple's talking about.



    Your electronic devices will cease to work after dipping below a certain constant voltage. At that point, you wouldn't be able to tell the difference between a totally discharged battery and one 40% charged without a voltmeter/multimeter. Apple obviously doesn't expect you to use anything other than the battery indicator on your computer, iPod or whatever.
  • Reply 6 of 7
    mmmpiemmmpie Posts: 628member
    I think the IBM info is really in regards to storage.

    LiIon batteries dont store well. The will self discharge, and then fail.



    As far as charging cycles goes, they shouldnt display a memory effect, but will fail to charge properly as time passes ( a cell should be good for 500 charge cycles or so ).



    As a liion is used its chemical structure changes ( I think hydrogen atoms migrate out of the battery ). Charging it puts the hydrogen back into place. This physical process causes damage to the crystaline structure that holds the hydrogen.



    Scienetist recently found a new crystal structure that allows for many more charge cycles, at the cost of lower power density.



    My rule of thumb, if you can plug it in do so, you'll save some of your charge cycles.
  • Reply 7 of 7
    scottscott Posts: 7,431member
    Yea I'm not sure those two contradict one another. Apple says, "Recharge them when they are out of power." and IBM says, "Don't store them discharged." It's almost the same thing.
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