Hatin' on lithium ionOriginally published 2004 in Atomic: Maximum Power Computing Last modified 03-Dec-2011.
Most of the key components of modern electronic devices - tough materials, electric motors, displays, sensors, integrated circuits - have improved out of sight in the last few decades. But batteries haven't.
If they had, we wouldn't still be driving cars with wet lead acid batteries under the bonnet, waiting to drip ghastly liquid on us as we lie pinned under our inverted vehicle in a ditch.
I'm just saying.
But wait, you say. We do have better batteries. We have lithium ion! And lithium polymer! And they rock! They're small, they're light, they charge pretty fast, and they don't suffer from memory effect!
Ah, yes. Well. I'm afraid you need some... re-education. Come inside with me, where the black helicopters can't see us.
I've ranted about memory effect before. So never mind that for now. I've another bone to pick with lithium-whatever rechargeable batteries.
Remember that iPod scandal from the end of 2003, when Casey and Van Neistat shot briefly to geekly fame with their claim that "iPod's Unreplaceable Battery Lasts Only 18 Months"?
Well, that particular rich-kid protest movement went over like a lead balloon, but the basic facts it was built on are valid. The iPod is like a lot of other little gadgets today, in that its battery can't be replaced without taking it apart (though at least iPod batteries have a plug-in cable, and aren't hard-wired to the circuit board). And all iPods - old, new, Mini, Photo, and Shuffle - use lithium ion batteries.
Lithium ion has good energy density (compared with other battery technologies, not compared with, say, a piece of firewood). The current iPod batteries pack more than three watt-hours into a battery that weighs less than 17 grams; that's about double the energy density of the best AA NiMH cells. That's why LiI (and lithium polymer, which for current cells is not much different) is everywhere.
The Big Problem with LiI, though, is that it's got less life expectancy than a Nexus Six replicant. Possibly only two years. Probably only three.
(Apple now have more stuff to say about batteries than they did during the Neistat flap, but you still won't find a mention of this lifespan limit - only that there is a lifespan limit, which Apple leave you free to think may be 57 years.)
Whether you use it hard or leave it on the shelf, there's a good chance a LiI battery will be so degraded as to be pretty much useless after a couple of years. And that's a couple of years after it's made, not a couple of years after you buy it.
That last part is a bit of a land mine, even if your gadget has a separate, snap-in battery. If your old battery dies of old age, and the manufacturer's moved on from that particular form factor of battery, and no third party manufacturer's selling new or freshly re-celled batteries to suit, you're probably screwed. There may well be "new old stock" LiI batteries in the original sealed packaging out there, but they'll all be useless.
Assembling your own LiI batteries is not necessarily possible, even if you're comfortable with soldering other kinds of batteries together. LiI packs often have internal electronics that keeps track of the battery condition; if you can't reset the battery condition firmware, new cells won't be seen as having any more capacity than the old ones. And the new cells had better be similar enough to the old ones that the charger doesn't make them misbehave.
(Misbehaviour, for LiI packs, often involves smoke.)
If you end up in this situation, you could also hack up a NiMH pack and stick it on with Velcro. A nominal-3.7V LiI cell can very probably be successfully replaced by three 1.2V NiMH cells in series. But you'll need a new charger, and the whole operation is a bit too Mad Max for most people.
Fortunately, the limited lifespan of LiI matches the ephemeral nature of most gadgets at the moment. Maybe, by the time when we're all jacking into cyberspace to go shopping for new Zeiss eyes, many classes of gadget will have reached the same maturity currently enjoyed by wristwatches and handguns. Then, it'll be perfectly reasonable to use high-tech items that were made decades ago.
Right now, though, a three year hard limit on battery life is not a tremendously big deal. Even a two-year-old mobile phone or MP3 player isn't a very exciting product right now.
But, heck, the thing probably still works. If you're still perfectly happy with your two megapixel digital camera or 650MHz P-III laptop, you're going to be pretty honked off if it turns out to be impossible to get new batteries for it - and even more irritated if you buy a few dud "new" batteries before you figure that out.
You young whippersnappers may not believe me, but I've got NiMH AAs here that I've been using hard for four whole years. They don't have anything like their original capacity left, but they're not weak enough to be useless yet. And modern sealed nickel cadmium cells were invented in 1947; they're pretty darn mature now, and very durable.
Everyone's still waiting for a really good portable power storage technology - fuel cells, anyone? In the meantime, we're still stuck with lithium-whatever. But it pays to bear in mind that a widget that runs from humble AAs may not be as slim and sexy as a LiI-powered version of the same thing, but if some other major component of the device hasn't dropped dead three years from now, at least you'll still be able to get batteries for it.