18 May 2015


One of the joys of cable TeeVee is the wealth of re-runs on view. I've had a soft spot for the original "Law and Order", muchly because of some really creepy bad guys. And girls. Over this weekend I caught the last few minutes of Killerz, in which a juvenile girl turns out to be a psychopath. Kills a boy who crosses her, and stuffs a battery in his mouth to wake him up. Or so the defense asserts. The actor, Hallee Hirsh, I hadn't seen before or since, but I wouldn't want to meet her in a dark alley.

But, this missive is about batteries, and the things they power. Killer apps, not killer kids.

Now that the Apple Watch sorta, kinda is out in the wild, the partisans on both sides have given full voice to their causes. The zealots talk about the Watch being game changing and all that. Turns out, not yet counting the Watch's specific implementation, that wrist reading heart rate isn't such a slam dunk. For the Watch, issues persist.

Those saying that blood pressure and blood sugar monitoring are right around the corner? Yeah, right. Not in an Apple Watch formfactor.

Which brings us to the notion, often asserted, that the Watch is soon to be a standalone replacement for the smartphone. Remember Dick Tracy? The issue remains: to power a smartphone-like device one needs smartphone mAh. So, one might expect an order of magnitude of energy density needed to power a wrist phone. Not yet, which says 205 mAh for the Watch. 2,000 to 3,000 is the range for smartphones. Granted that the display differences mean the Watch wouldn't need the full boat, but one still has to assume that the V in VLSI gets to be very much more V than it already is just to put the functions on the wrist. Yeah, right.

Is there an, as yet undisclosed, chemistry (that won't blow up or incinerate) that is significantly greater in density? Do we know all the elements of the periodic table? Here's one that claims to be "better", but not any more dense.

For instance:
Engineers and chemists have long known that using lithium metal as the anode in a rechargeable battery -- as opposed to the conventional carbon materials that are used as the anode in conventional lithium-ion batteries -- can dramatically increase its energy density. But using lithium metal, a highly reactive solid, in conjunction with a liquid electrolyte is extremely hazardous because it increases the chance of a thermal runaway reaction that can result in a fire or an explosion.

Chester Gould just drew a picture of a wrist radio, and made it work. The real world is a bit pickier.

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