Hi all, (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.) 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. Sincerely, Ron On 5/9/2012 1:12 PM, tz wrote: > 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. > > 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. > > On Wed, May 9, 2012 at 12:55 PM, Dave Taht > wrote: > > On Wed, May 9, 2012 at 9:47 AM, Eric S. Raymond > wrote: > > Dave Taht >: > >> What would be the change in cost and delay in manufacturing to > switch to > >> using a supercap, rather than battery? > > > > Why would a supercap be better? > > Effective lifetime of... forever. no need for replacement. insanely > fast recharge. smaller (probably). What's not to like? > > I am not in a huge hurry to get into manufacturing, and I merely > wanted to cost out what what it would do to the bom, any changes to > the PCB, and get an estimate for the time it would take to do. I think > it will bump the unit cost up slightly, > but what price, forever? > > > -- > > Eric S. Raymond > > > > -- > Dave Täht > SKYPE: davetaht > US Tel: 1-239-829-5608 > http://www.bufferbloat.net > _______________________________________________ > Thumbgps-devel mailing list > Thumbgps-devel@lists.bufferbloat.net > > https://lists.bufferbloat.net/listinfo/thumbgps-devel > > > > _______________________________________________ > Thumbgps-devel mailing list > Thumbgps-devel@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/thumbgps-devel > -- (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