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Re: Should I completely discharge my laptop battery?

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Once upon a time on usenet mike wrote:
> On 2/7/2015 5:24 PM, ~misfit~ wrote:
>> Once upon a time on usenet mike wrote:
>>> On 1/12/2015 3:18 PM, ~misfit~ wrote:
>>>> Once upon a time on usenet mike wrote:
>>>> [total snip]
>>>>> Are we having fun yet?
>>>>
>>>> Thanks Mike. I've copied that to notepad and saved it for when I
>>>> have a bit of time to play with.
>>>>
>>>> I have a couple of these too
>>>> http://www.dx.com/p/mp1405-5v-1a-lithium-battery-charging-board-blue-black-219454#.VLRT1MlZqUc
>>>> and used one for re-powering a mini rotary tool I got cheap that
>>>> used 3x small NiCad cells in shrink-wrap, the total size of which
>>>> was similar to a single 18650 but had little 'power' and didn't
>>>> hold much charge. I bought a new solder-tab Panasonic cell for
>>>> that job as I didn't know how good my slavaged cells were and it's hard 
>>>> to
>>>> open up the modded tool.... However it doesn't seem to like
>>>> running a motor from the 'out' pads
>>>> - maybe it's something to do with the brushes and how it works? I
>>>> tried three of these PCBs for the job and they all didn't work
>>>> right. In the end I had to wire a small momentary contact switch
>>>> between the B+ and OUT+ pads to start the motor. Once it's started
>>>> it runs fine from the 'OUT' contacts. <shrug> As you can probably
>>>> tell I only have basic knowledge (but try hard
>>>> to not take risks - I'm very aware of the inherant dangers with
>>>> Li-Ion tech and the potential for 'thermal runaway').
>>>>
>>>> Cheers,
>>>>
>>> The website was translated into ChEnglish and doesn't make a lot of
>>> sense, but if I were to guess...
>>>
>>> How are you switching the power?
>>>
>>> If you're switching between the battery and the board,
>>> that may be your problem.  Sounds like the board has to be powered
>>> up continuously.  I'd measure the drain from the battery in the
>>> off state.  May be inconsequential...maybe not.
>>>
>>> If you're switching between the board and the motor, the turn-on
>>> transient from the motor may exceed the 3A current limit.  Maybe a
>>> big cap across the out pads will help.
>>
>> Mike, quick question as I'm going to use another of these modules for
>> controlled discharge of Li-Ion cells using a motor as a load... What
>> value do you mean when you say 'a big cap'?
>>
>> Cheers,
>>
> That's not a simple question.  Motor load is complex. I have no idea
> how the control board works.
> The spec alludes to a 3 amp protection limit.  If your motor starting
> current exceeds 3A, you need to limit that somehow.  A cap can help,
> but it might take a very big one.  I'd start with 100uF and experiment
> from there.  But a cap won't help for a constant load like locked
> rotor.

Thanks again. I really appreciate your input.

> The board says 3A Protection.  It's designed for a Maximum of 1A load.
> You can be sure if it would survive much over that, the spec would be
> higher.  Monitor the FET temperature to see if it will melt off the
> board.

That's what I have an infrared thermometer for. ;)  Well, that and to see if 
my LEDs are running at acceptable temps.

I just dismantled a completely dead Dell nine cell battery pack. It came 
with a laptop that I reburbished and sold on a couple of years ago. The 
laptop wouldn't have a bar of it, said battery dead and needs replacement. 
When dismantled I saw it was wired 3s/3p and three of the cells have 0.00v 
charge and simply won't take a charge no matter what I try - they just get 
hot.

However the other six (Samsung 18650-26 cells, 2,600 mA/h) seem great. They 
were sitting at 3.2v when the pack was dismantled and they came up really 
quickly in the charger. There's lots and lots of capacity left in all of 
them - a really good score. If I had to guess I'd say that the pack had been 
left in storage in a discharged state for some time and the pack contol 
circuitry took it's power from just that group of three cells. When it 
completely drained those it flagged the pack as dead.

Oh, I upgraded my charger to a Nitecore D2. Now I have a reasonable 
collection of usable Li-Ion cells it seemed like a good investment.

Cheers,
-- 
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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