Re: HP 29-C

[Michael Meyer]

Gotta mention here, again, my good luck so far in replacing the cells in HP packs with 1.5V Lithium AA batteries. I've never seen one leak (though I suspect the legend of the nuclear explosion would apply here...), they have an incredible durability if the useable temperature range is any indication (0 degrees to 212F), and a ten to twenty-year or more storage life. They are much lighter than alkaline AA's, and have approximately five times the power capacity. Has completely removed the necessity of charging a calc and they're always at full power. (I've only done this with my "users". The collection has the dutifully rebuilt NiCD's in separate storage.

I'd hypothesized the lithium's stability and safety in an earlier thread, but of course, haven't used any long enough to know for sure. I do have some very early design lithium AA's in flashlights over 5 years old and still powering up strong.

I'll let everyone know, in about 20 years, if the ones in my spare HP-25 and HP-67 have leaked or not. (Does anyone know what WOULD leak?) BTW... the few extra tenths of a volt don't seem to have hurt any of the calcs. Again, yet: but they can't be worse than alkalines...

Michael

[David Smith]

Just make REAL sure that nobody accidentally connects one to a charger cord... lithium is the most volatile metal known. It makes sodium look tame and can spontaneously combust in humid air. Although they probably would not acutally explode if charged, the end results would be much the same. Perhaps a piece of tape over the charger port would be a good thing. I would use Kapton tape used to mask gold fingers on circuit boards being flow soldered. The adhesive seems very stable and is designed to not leave residue behind.

[Michael Meyer]

Thanks for the reminder, David! I hadn't even considered or worried about that, as I am the only one in the house using my calculators.... but the kids will be older soon. It would be-- potentially-- quite a disaster!! (Hmmmm.... sounds like a fun science project to me. I have several semi-functional TI's in my junk bin that would still charge a pack. I wonder what would happen if I charged one outside... I might have to be sure it's around July 4th....)

If you see a large mushroom-like cloud, you'll know I accidentally hooked one up to a charger... <grin>.

Michael