bryce@COGSCI.BERKELEY.EDU (Bryce Nesbitt) (09/03/87)
[If you reply, be sure to strip off comp.sys.amiga from the distibution!] > In article <4410010@hpcvcd.HP> charles@hpcvcd.HP (Charles Brown) writes: >> >>...that battery should last somewhere in the range of 10-30 years... >>(="=) bryce@hoser.berkeley.EDU -or- ucbvax!hoser!bryce > >I find this hard to believe. Shelf life for Lithium batterys is about >three years, and those are long life batteries. Ok! There has been widespread disbelief in my statement that this battery could last 10-30 years. I can't argue the technical points, so I will just list my source; the data sheet for the chip. Thomson Components-Mostek claims to have some special longer life batteries. In the data sheet they have a formula for discovering battery life. It depends primarily on temperature. I can't reproduce the charts here, so if you want to see them get data for the MK48T02. Assuming a powered system, with no drain on the battery, wear out is almost exclusively a function of temperature. The chart goes from slightly over 2 years at 75 C to to over 100 years at 5 C. The three year point is at 70 C. When the battery is actually backing up the ram, consumption is a factor. Again the colder it is, the longer things will last. In a simple case with a constant temperature of 25 C and a 65 percent duty cycle the chart shows 10 years. At a zero percent duty cycle (always backing up) the life at 25 C is shown as three years. For more exact figures, see the data sheet. oo bryce@hoser.berkeley.edu -- ucbvax!hoser!bryce if "hoser" does not work, try "cogsci" If this article is mangled, let me know. This rn was finished compiling 10 minutes ago and may not be fully installed yet.
bilbo@pnet02.UUCP (09/07/87)
So lets mount the battery off the board in the frig...
Bill :-)
UUCP: {hplabs!hp-sdd!crash, seismo!scgvaxd!cadovax}!gryphon!pnet02!bilbo
INET: bilbo@pnet02.CTS.COM
*Bilbo*
(Recombinant Hobbit)john@hpcvlo.HP.COM (John Eaton) (09/08/87)
>>>>>>> >> >>...that battery should last somewhere in the range of 10-30 years... >>(="=) bryce@hoser.berkeley.EDU -or- ucbvax!hoser!bryce > >I find this hard to believe. Shelf life for Lithium batterys is about >three years, and those are long life batteries. ---------- I find it hard to believe that anyone would bother to design a 30 yr clock for a computer. Think of where you were 30 years ago and what computer you were using then. Are you still using the same system? I didn't think so. There are other parts of the computer that become obsolete long before the battery gives out. If the design goal is for the system not to lose time for 30 years then you also have to consider the effect of crystal tolerance. Your standard 20ppm clock crystal will be off by over 5 hours over the course of 30 years and this will require user intervention anyway. 30 years is not as useful as it sounds. John Eaton !hplabs!hp-pcd!john