How about a Li-Ion battery with a charging IC from Maxim? Good density and easy recharging (the chip and a couple of caps are all you need), along with an easily usable voltage (3-3.7V for almost the entire life). For the good, but not cheap (but it's rechargable remember), route, Mouser has a number of different options. This one is 1.7Ah for $13.46: http://www.ultralifebatteries.com/documents/techsheets/UBI-1014_UBP103450.pdf For the cheap, but maybe not good route, AllElectronics (or maybe it was Electronics Goldmine) had surplus batteries awhile back that were OK. The MAX1551/1555 Li-Ion charging ICs are ridiculously easy to use (http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4002). You could either learn to deadbug wire the SOT23/5 package or buy a little breakout board to solder it to (http://www.sparkfun.com/commerce/product_info.php?products_id=717) or get your own PCB done. Or you could just buy this: http://www.sparkfun.com/commerce/product_info.php?products_id=726 Maxim will give you samples of the chip for free though if you go one of the other routes. -n. On Fri, Jun 27, 2008 at 3:46 AM, Jinx wrote: >> given a 100% efficicient converter from 1.5V to 5V (which of >> course doesn't exist), drawing 500ma out would require 500ma* >> 5V/1.5V = 1666ma input current (TANSTAAFL!). > > ISTR Tomas reckoned 800mW for the circuit, so the conversion > process might explain the "Why not millwatt hours ?" thread > > 800mW out will be (800mW/conversion efficiency) in, more or less. > 533mA @ 1.5V would be drawn from the AA to make 160mA @ > 5V, giving a realistic lifetime of 3-4 hours at a reasonable conversion. > Less battery current when fresh than when it's running out of puff. I > think battery capacity rating is down to 1V terminal voltage but you'd > have to check that > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist