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 <[email protected]>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 < > [email protected]> 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" <[email protected]> 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 <[email protected]> >>> <[email protected]> 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 >>> >>> >>> >>> _______________________________________________ >>> altusmetrum mailing >>> [email protected]http://lists.gag.com/mailman/listinfo/altusmetrum >>> >>> >>> >>> _______________________________________________ >>> altusmetrum mailing list >>> [email protected] >>> http://lists.gag.com/mailman/listinfo/altusmetrum >>> >>> >> _______________________________________________ >> altusmetrum mailing list >> [email protected] >> http://lists.gag.com/mailman/listinfo/altusmetrum >> >> > > _______________________________________________ > altusmetrum mailing list > [email protected] > http://lists.gag.com/mailman/listinfo/altusmetrum > >
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