BATTS2.DOC by stevev@miser.uoregon.edu [Steve VanDevender] Date: 01 Mar 1993 [Note: There is a file called BATTS.DOC on Goodies Disk #8 which proposed that battery drain is accelerated by improper orientation of the HP 48 relative to the direction of the ether wind. Here's another hypothesis which is, uh, just as serious... -jkh-] In article <1993Feb27.184413.12699@fuug.fi> an1060@anon.penet.fi writes: I would like to know if the HP-48's power drain on the batteries is significantly increased by more programs/data stored in RAM... If so, then can someone quantify this relation?? We're glad you asked that, Mr. Mantell, ahem, we mean Mr. an1060! As the chief research scientist at Speed Merchant Laboratories (a wholly owned subsidiary of Speed Merchant, Inc.) I have been studying this question for some time. We at Speed Merchant use a variety of Hewlett-Packard equipment, and HP 48SX calculators are standard issue to our research and engineering staff. Corporate pennypinching has forced us to ration batteries to our staff, and therefore finding ways to extend battery life has become an issue of some concern. We have run a series of experiments on this matter, and here present our findings: HP 48SX calculators were loaded with special memory patterns, ranging from all zeros to all ones, leaving some available memory to allow calculator operation, on calculators with no expansion memory, one 128K memory card, or two 128K memory cards. The time from installation of fresh batteries (we used Kodak Supralife brand) until the low battery light came on was then recorded; due to differing rates of use this time shows some variation which was quite consistent. HP 48SX with 32K 160K 288K % of binary 1s in memory 0% 2160 hrs 2160 hrs 2160 hrs (+/- 720 hrs) 25% 90 days 90 days 90 days (+/- 30 days) 50% 12 weeks 12 weeks 12 weeks (+/- 4 weeks) 75% 3 months 3 months 3 months (+/- 1 month) 100% 0.25 years 0.25 years 0.25 years (+/- 0.83 years) As you can see from the rapidly decreasing numbers, increasing proportions of binary 1s in calculator memory makes a tremendous difference in battery life. In general the 25-50% figures represent typical usage, where memory is kept full or nearly full assuming that stored data has a distribution of roughly half ones and half zeros when expressed in binary form. As a result of this research we are now working on ways to reduce the number of binary 1s stored in HP 48 calculator memory using various data compression techniques, but these will not be on the market for some time. Until then, we can suggest a few methods for reducing the number of 1s stored in your calculator's memory: 1. If a GROB contains more dark pixels that light pixels, use the NEG command on it before storing it in memory, and use NEG again just before placing it into the display. NEG on GROBs will change dark pixels to light and light to dark; when used on a mostly-dark GROB this will then reduce the number of 1 bits needed to store it. 2. Use as few digits of precision as are needed in the problem at hand, and use the RND or TRUNC commands before storing results to truncate the excess digits and remove unneeded 1 bits. 3. Turn off unneeded display annunciators; besides requiring 1 bits in memory, activated annunciators also draw more power in the display. 4. Clear the PICT and stack whenever the data in them is unneeded. 5. Garbage collect frequently; don't wait until the heap is exhausted. Make it a habit to do MEM DROP every few keystrokes. We at Speed Merchant hope that this information has proven useful. Once again, look for our soon-to-be announced HP 48 software package that will automatically minimize the number of 1 bits in memory and thereby improve your battery life in typical usage from as little as 0.17 years to as much as 1440 hours! Steve VanDevender Chief Research Scientist Speed Merchant Laboratories a wholly owned subsidiary of Speed Merchant, Inc., manufacturers of the Speed Merchant 5000 -- the only wheelchair with a roll bar! -- Steve VanDevender stevev@greylady.uoregon.edu ---------- Resp: 3 of 3 by rrd@hpfcso.FC.HP.COM [Ray Depew] Date: 03 Mar 1993 Mr. VanDevender graciously provided us with battery usage numbers, but he omitted the weight of all those binary 1's. (You know, the more 1's in memory, the heavier the calculator weighs...) Perhaps Speed Merchant can follow-up with a report on the comparative weights of different brands of battery, and a recommendation on the optimum battery to use for longest life, fullest RAM and lightest 48SX. Now *there's* an engineering problem for you! Regards Ray Depew Integrated Circuits Business Division Hewlett Packard Co, Fort Collins, Colorado rrd@hpfiqa.fc.hp.com