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Hi all,<br>
<br>
(I'm copying this only to the thumb-gps list and to TZ, the most recent
commenter, as I don't know all the parties in the header of TZ's
message. You guys can forward it to whomever else may need to see it.)<br>
<br>
Speaking strictly as a potential user of the thumb-gps device and
amateur interested party, I would rather see a supercap, if feasible.
I hate the idea of devices having batteries that I have to worry about
failing in 5-10 years. I've had the cmos batteries fail in a few
computers, sometimes preventing them from booting. It can get really
ugly trying to revive them A good high efficiency dc-dc converter chip
should allow you to drain all but the last bit of energy from the cap
while maintaining whatever working voltage you need. I cannot speak to
size issues, as I have never designed a circuit board with one. The
GlobalSat BU-353 that I have has a supercap, I believe. Exact backup
time is not stated, but I believe it's a few days.<br>
<br>
Sincerely,<br>
<br>
Ron<br>
<br>
On 5/9/2012 1:12 PM, tz wrote:
<blockquote
cite="mid:CAFv7OihBDpT20Rnqy4J4_GvGzJwzU==H1KWy2fAVX24A7nwP=Q@mail.gmail.com"
type="cite">For a given size (and circuit board footprint) a supercap
will have much less capacity and it has an exponential voltage decay
curve, so it might have plenty of charge but not at a voltage that will
hold the data. This usually means hours, not days of backup.<br>
<br>
A good rechargeable lithium will last several years, maybe longer as
there will be no charge/discharge, maintains voltage until it is nearly
exhausted, and can hold the data for days or weeks.<br>
<br>
<div class="gmail_quote">On Wed, May 9, 2012 at 12:55 PM, Dave Taht <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:dave.taht@gmail.com" target="_blank">dave.taht@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div class="im">On Wed, May 9, 2012 at 9:47 AM, Eric S. Raymond <<a
moz-do-not-send="true" href="mailto:esr@thyrsus.com">esr@thyrsus.com</a>>
wrote:<br>
> Dave Taht <<a moz-do-not-send="true"
href="mailto:dave.taht@gmail.com">dave.taht@gmail.com</a>>:<br>
>> What would be the change in cost and delay in manufacturing to
switch to<br>
>> using a supercap, rather than battery?<br>
><br>
> Why would a supercap be better?<br>
<br>
</div>
Effective lifetime of... forever. no need for replacement. insanely<br>
fast recharge. smaller (probably). What's not to like?<br>
<br>
I am not in a huge hurry to get into manufacturing, and I merely<br>
wanted to cost out what what it would do to the bom, any changes to<br>
the PCB, and get an estimate for the time it would take to do. I think<br>
it will bump the unit cost up slightly,<br>
but what price, forever?<br>
<div class="im HOEnZb"><br>
> --<br>
> <a href="<a moz-do-not-send="true"
href="http://www.catb.org/%7Eesr/" target="_blank">http://www.catb.org/~esr/</a>">Eric
S. Raymond</a><br>
<br>
<br>
<br>
</div>
<div class="im HOEnZb">--<br>
Dave Täht<br>
SKYPE: davetaht<br>
US Tel: <a moz-do-not-send="true" href="tel:1-239-829-5608"
value="+12398295608">1-239-829-5608</a><br>
<a moz-do-not-send="true" href="http://www.bufferbloat.net"
target="_blank">http://www.bufferbloat.net</a><br>
</div>
<div class="HOEnZb">
<div class="h5">_______________________________________________<br>
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<a moz-do-not-send="true"
href="mailto:Thumbgps-devel@lists.bufferbloat.net">Thumbgps-devel@lists.bufferbloat.net</a><br>
<a moz-do-not-send="true"
href="https://lists.bufferbloat.net/listinfo/thumbgps-devel"
target="_blank">https://lists.bufferbloat.net/listinfo/thumbgps-devel</a><br>
</div>
</div>
</blockquote>
</div>
<br>
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</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
(To whom it may concern. My email address has changed. Replying to former
messages prior to 03/31/12 with my personal address will go to the wrong
address. Please send all personal correspondence to the new address.)
(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and
such. I don't always see new messages very quickly. If you need a
reply and have not heard from me in 1 - 2 weeks, send your message again.)
Ron Frazier
timekeepingdude AT techstarship.com
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