RE: My previous "Anyone care to guess as to whether I'd be able to open a
pack up and harvest one of
the cells?"
On re-reading it seems poorly composed.
What I *meant* is:
"Is opening up an electric RC model airplane lithium battery with 2 or 3
cells in series
likely to be fairly easy for someone that isn't afraid of
http://www.altusmetrum.org/Documents/FixBattery/
?
And/or have any thoughts or caveats re the above.
On Wed, Sep 11, 2013 at 10:47 AM, Peter Hackett <
peter.hack...@cal.berkeley.edu> wrote:
> Thanks Bryan.
>
> I don't have any old laptop batteries, but I do have some old electric RC
> model
> airplane packs. I think the ones I have are two or three cells in series.
> (Thunder Power I think)
>
> Anyone care to guess as to whether I'd be able to open a pack up and
> harvest one of
> the cells?
>
>
> On Tue, Sep 10, 2013 at 10:06 PM, Schmidt, Bryan
> <bts-rock...@bluefx.com>wrote:
>
>> Potential hack solution... I have several times taken apart old laptop
>> batteries to repurpose the individual cells inside. Quite old ones will
>> have cylindrical Li-Ion cells, 4.1V charge cutoff. Newer will have several
>> Li-Poly cells. In almost all cases, the protection circuitry is
>> centralized on a piece of PCB. So (carefully!) cut the leads and you can
>> get at individual unprotected cells. While these are bulky, at old age
>> they still have quite a lot of capacity and into a short can still put out
>> pretty amazing current.
>>
>> Personally I'd go to the RC store and find something that has a high
>> current rating, such as for small RC helicopters, and just pay careful
>> attention to polarity as already suggested. Since you are using ematches,
>> you probably don't need much current to set them off, and they are fairly
>> likely to be open-circuit after they are fired, so *likely* you never draw
>> more than the protection circuit is rated for anyway. However, lots of
>> variables, and easy to armchair advise from here...
>>
>> Good luck in any case.
>> -Bryan
>>
>>
>>
>>
>> On Tue, Sep 10, 2013 at 5:31 PM, Plugger Lockett <
>> plugger.lock...@gmail.com> wrote:
>>
>>> I'm pretty sure I packed a 600mAh spare if you think that will suit your
>>> needs. I'm Andrew Hamilton and will be in the Australian camp. See you on
>>> the playa!
>>> On 11/09/2013 8:40 AM, "Sam Fineberg" <s...@fineberg.net> wrote:
>>>
>>>> Peter,
>>>> You might ask Mike @ BAR. He had some Telemetrium gear the last time I
>>>> looked. He might be able to pull a battery out of a bundle kit if you
>>>> asked nicely.
>>>>
>>>> Sam
>>>>
>>>> On 9/10/2013 3:23 PM, Keith Packard wrote:
>>>>
>>>> Peter Hackett <peter.hack...@cal.berkeley.edu>
>>>> <peter.hack...@cal.berkeley.edu> writes:
>>>>
>>>>
>>>> I'm off to Black Rock on Thursday. Not sure I'll be able to replace it by
>>>> then.
>>>> (I'm assuming it would be hard to find the right battery locally)
>>>>
>>>> Yeah, we use the same connector as some helicopter batteries, but the
>>>> polarity is reversed, which would destroy both battery and board if you
>>>> plug them together.
>>>>
>>>> Bdale has a pile of current stock, but he's in California until tomorrow
>>>> evening. I don't have any of the larger size left at this point or I'd
>>>> offer to ship one from here.
>>>>
>>>> We get them from SparkFun though, and they do offer overnight shipping:
>>>>
>>>> https://www.sparkfun.com/products/341
>>>>
>>>> However, if you want to use them to fire charges, you'll need to remove
>>>> the current limiter board. If left in place, the battery will shut down
>>>> as soon as you try to fire a charge, leaving the board dead in the
>>>> air. Older SparkFun batteries had a different protection circuit which
>>>> worked fine with TeleMetrum, newer SparkFun batteries nearly always fail.
>>>>
>>>> It's a pretty simple soldering job, if you're up for the adventure.
>>>>
>>>> http://www.altusmetrum.org/Documents/FixBattery/
>>>>
>>>> Anyone want to chime in on whether AAA's will be big enough?
>>>>
>>>> Also, I guess I should be concerned about battery internal resistance.
>>>> Will 3 standard alkaline
>>>> batteries in series be able to provide enough current to light the
>>>> e-matches?
>>>>
>>>> Not recommended for a couple of reasons:
>>>>
>>>> *) TeleMetrum will try to charge them when plugged in over USB. There's
>>>> no way to disable the charger, and the board cannot run without a
>>>> battery in place.
>>>>
>>>> *) AAA batteries have a higher internal resistance than lithium
>>>> polymer batteries, which means if you try to fire an e-match, the
>>>> voltage seen by the board will drop low enough to reset the board.
>>>>
>>>>
>>>> RE over-charge:
>>>>
>>>> Can that happen using the TeleMetrum to do the charging?
>>>>
>>>> The charge controller on TeleMetrum shouldn't be able to overcharge an
>>>> undamaged battery. I've left them plugged in for weeks at a time without
>>>> problems.
>>>>
>>>> -keith
>>>>
>>>>
>>>>
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