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Re: Should I completely discharge my laptop battery?

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Once upon a time on usenet andymhancock@gmail.com wrote:
> Mike, Misfit,
>
> That was an overwhelming amount of insight into how batteries degrade.
> I'm not really an electronic technology (anymore), but I appreciate
> your sharing.  I don't anticipate going the lengths of
> resuscitating a battery, though I'm sure that the information will
> give the more technologically oriented readers some good ideas.
>
> About Misfit's advice that one doesn't need to discharge much below
> 5%, this seems to imply (to me) that the charging circuitry isn't
> losing track of what constitutes a low charge, it is losing track of
> what constitutes a full charge.  Is this correct?

Sort of. As Mike pointed out older cells can develop high internal series 
resistance (ISR). So it all depends on what your particular battery pack 
uses to trigger various states. Most use voltage and, if the ISR has risen, 
at lower voltages the cells still have the energy stored but can't deliver 
it at high load levels. So, with warnings turned off, when the computer asks 
for quite a few amps (CPU usage goes up) it can die suddenly. The power is 
still in the battery but it can only deliver it at low rates of current.

It's complicated stuff really and isn't helped by, as Mike says, laptop 
manufacturers err on the side of caution so will often have their control 
circuitry (in both battery pack and laptop) tell you a battery has less 
capacity than it does - and so limit your access to lower voltage states as 
the cycle count goes up. They make a lot of money out of selling replacement 
batteries. This doesn't take into account however what conditions the 
battery has been used under and whether it has been deep-cycled or 
constantly topped off.

(The latter is the default for most laptops and is really bad for 
batteries - especilly at raised temps, which a lot of batteries run at - and 
increases their ISR more quickly than if the batteries were cooler and were 
kept closer to the ideal state of charge for longevity - around 40% charge.)

My experience is with ThinkPads and the newer ones (post 2006 / T43 and 
later) allow the user to manually set the charge parameters. If you do that 
as I do - so the thing doesn't constantly charge to full every time the 
charge drops below 95% - then the batteries last twice as long at least. 
They also have software for 'battery reset' - where they fully charge / 
discharge the pack and recalibrate the control circuit built into the pack - 
basically what you're trying to do now.

So, not knowing how your system manages it's battery pack I can only give 
generalised advice. Almost all laptop battery packs use solder-tab 18650 
cells. I wish I could design and build a pack for my laptops that uses 
replaceable 18650s (like my flashlight does) and contained circuitry to 
manage them. Much like replacing AA cells in a remote controller. However as 
Mike pointed out the manufacturers make big money selling replacement 
batteries. :-/

> And this risk of bricking the battery -- from reading your responses,
> it seems that this is a very plausible risk even if I just run it to
> the point where the computer shuts down (not putting it in a drawer
> for half a year).  It's a bit ambiguous, because one can interpret
> this as the point at which there is "no usable power left", but then
> again, there was that story about high internal resistance developing
> a high voltage drop once the laptop draws current to do shutdown
> activities.  As I said, I've got the laptop set to do nothing when it
> reaches the Reserve battery level, but I have zero trust that windows
> actually does nothing in the same way as it does if you were to just
> yank the battery.

Are you not running the OEMs battery mangement software?

> Anyway, given this ambiguity, it looks like 5% is what you recommend
> as a good level to discharge to if I just want to recalibrate.

Yeah, it might not reclaim a huge amount of charge 'marked bad' but it also 
shouldn't brick your battery pack.
-- 
Shaun.

"Humans will have advanced a long, long, way when religious belief has a 
cozy little classification in the DSM."
David Melville (in r.a.s.f1) 

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Should I completely discharge my laptop battery? andymhancock@gmail.com - 2014-12-30 11:53 -0800
  Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2014-12-31 13:35 +1300
    Re: Should I completely discharge my laptop battery? andymhancock@gmail.com - 2014-12-31 11:06 -0800
      Re: Should I completely discharge my laptop battery? andymhancock@gmail.com - 2014-12-31 11:54 -0800
        Re: Should I completely discharge my laptop battery? andymhancock@gmail.com - 2015-01-01 15:13 -0800
      Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-01-01 12:29 +1300
    Re: Should I completely discharge my laptop battery? mike <ham789@netzero.net> - 2014-12-31 12:05 -0800
      Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-01-01 12:55 +1300
        Re: Should I completely discharge my laptop battery? andymhancock@gmail.com - 2015-01-01 14:51 -0800
          Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-01-02 14:16 +1300
            Re: Should I completely discharge my laptop battery? andymhancock@gmail.com - 2015-01-01 18:11 -0800
              Re: Should I completely discharge my laptop battery? mike <ham789@netzero.net> - 2015-01-02 01:15 -0800
                Re: Should I completely discharge my laptop battery? andymhancock@gmail.com - 2015-01-02 09:34 -0800
                Re: Should I completely discharge my laptop battery? mike <ham789@netzero.net> - 2015-01-02 10:46 -0800
                Re: Should I completely discharge my laptop battery? andymhancock@gmail.com - 2015-01-02 14:25 -0800
                Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-01-04 12:28 +1300
                Re: Should I completely discharge my laptop battery? andymhancock@gmail.com - 2015-01-03 16:48 -0800
                Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-01-07 14:47 +1300
                Re: Should I completely discharge my laptop battery? mike <ham789@netzero.net> - 2015-01-06 19:38 -0800
                Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-01-09 13:36 +1300
                Re: Should I completely discharge my laptop battery? mike <ham789@netzero.net> - 2015-01-08 17:34 -0800
                Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-01-10 14:59 +1300
                Re: Should I completely discharge my laptop battery? mike <ham789@netzero.net> - 2015-01-09 20:22 -0800
                Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-01-13 12:18 +1300
                Re: Should I completely discharge my laptop battery? mike <ham789@netzero.net> - 2015-01-12 17:20 -0800
                Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-01-15 13:35 +1300
                Re: Should I completely discharge my laptop battery? mike <ham789@netzero.net> - 2015-01-14 17:37 -0800
                Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-01-16 12:33 +1300
                Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-02-08 14:24 +1300
                Re: Should I completely discharge my laptop battery? mike <ham789@netzero.net> - 2015-02-07 21:02 -0800
                Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-02-11 11:09 +1300
                Re: Should I completely discharge my laptop battery? "~misfit~" <shaun.at.pukekohe@gmail.com> - 2015-01-03 11:47 +1300

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