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> 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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