Re: Should I completely discharge my laptop battery?

From	mike <ham789@netzero.net>
Newsgroups	comp.sys.laptops
Subject	Re: Should I completely discharge my laptop battery?
Date	2015-01-08 17:34 -0800
Organization	A noiseless patient Spider
Message-ID	<m8nb7e$59c$1@dont-email.me> (permalink)
References	(11 earlier) <m89tuh$1v4$1@dont-email.me> <99a8bc87-4630-484f-93ac-5088c4fce22c@googlegroups.com> <m8i37d$ja6$1@dont-email.me> <m8i9mu$1nn$1@dont-email.me> <m8n7pj$qom$1@dont-email.me>

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On 1/8/2015 4:36 PM, ~misfit~ wrote:
> Once upon a time on usenet mike wrote:
>> On 1/6/2015 5:47 PM, ~misfit~ wrote:
>>
>>>
>>> Anyway now I have another six 1st tier 18650 cells to play with.
>>> Learning their (remaining) capacity is the hardest part for me. If I
>>> wasn't so broke I'd buy a charger / analyser like the Maha Wizard
>>> One device that I bought ages ago for managing my Eneloops (I have a
>>> strong dislike of primary cells). However as it is I'm stuck with a
>>> 'dumb' charger that just charges until voltage is ~4.2v. Then I to
>>> do a timed discharge in a flashlight. :-/ Very crude.
>> But effective.
>>
>> I built a setup with programmable power supply and programmable load.
>> Makes nice graphs,but not clear that they have any value beyond
>> curiosity.
>
> I like to know cell capacity as I have some applications wher they run in
> parallel.

Try to use cells from the same pack and don't sweat it.  They're already
paralleled in pairs in many packs.  Unless a cell is shorted, it's not a 
huge risk.

The time you want 'em matched is when you run them in series.  If they're
not matched, the pack gets imbalanced and can overdischarge or overcharge
one.

I avoided all that hassle with my bike light.  I put 4 18650 cells
in a plastic pipe and brought out the wires of all cells to a DB-9
serial connector.  The light runs them in series.
The charger charges them in parallel.  I did put 4 1.5 ohm resistors
in the charger plug so that if something shorted, it would blow the
resistor instead of the battery.

>
>> I do have a suggestion.
>> use a variable power supply and a diode.
>> set the power supply so the output of the diode is at the low
>> limit discharge voltage. Set the current limit sufficiently high
>> to run the discharge load.

If you don't have an adjustable power supply, it doesn't matter.
The purpose of the diode and supply is to prevent overdischarge.
You set the power supply so that the diode is off and the supply
is completely disconnected during the whole test.
If you're gonna sit and watch a voltmeter during the whole test,
you don't need it.

When you do need it is when you aren't watching.  When the phone rings.
Or the wife gets freaky.
Or when the kid falls and hurts himself.
If you get distracted, the diode eventually turns on, supplies
all the load current and saves your
cell from overdischarging below whatever voltage you set minus the diode 
drop.

>
> That first thing sounds good but I'm a little challenged when it come to
> electronics. I know basics (enough to make audio crossovers etc.) and have
> some components around the place.
>
> Would you be so kind as to explain in a bit more detail? I'd be obliged.
>
> Cheers,
>
Bottom line is that it takes a lot of equipment to get any meaningful data.
I had fun doing it, but it's not clear that the data made any real 
difference in the
applications.

Thread

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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