Ok, since I'm on a rampage with ideas lately, here's another idea to chew on. One of the best battery systems I've run into out there is a capacitor based battery. Obviously power density leaves something to be desired on some of them, but some of the newer capacitor technologies, especially those based around the new carbon nanotubes, have a crazy high density. They have also solved the power arch problem of the older capacitors (ie, power output decreases relative to the amount of remaining power as charge decreases, instead of remaining steady like normal batteries), which means that rechargeable batteries based on capacitor technology is now possible.

And I know several guys who have successfully done this both with the newer capacitors, and the older ones. And since there are flat capacitors, I know we could easily build a capacitor battery in an n810 form factor (or n800 too!) with some good run times and good power density. We'd still likely need a power output regulator to keep the voltage exactly where it needs to be, but that's a small thing to do and wouldn't consume much space.

And I'm sure some of you are asking why I'd be crazy enough to consider such an idea. Well, for several reasons.

1) Capacitors have a much better charge to storage ratio. Like 90% I think. In other words, of all the power put into a capacitor to charge it, 90% is stored, and the other 10% is passed back to the system. Normal rechargeable batteries have like anywhere from 1% up to maybe 20% tops. That's a lot of wasted energy when charging a battery. So in short, you'd be able to recharge your NIT from dead in like 5-10 minutes instead of 2-3 hours, and it wouldn't change how your NIT charges. It would simply make better use of the power being pumped through it to charge the device.

2) Capacitors have about the highest power return rate of any rechargeable storage device. Of all the energy that's put into it, about 99% can be taken back out, and it can be taken out at whatever speed you need it to. Heck, a capacitor could dump its entire load of stored energy if asked to in one split second if the need was there, so higher demand processes will get all the energy they need, just like lower demand ones will without heating up the battery or causing other issues. Now I'm sure we'll need to put a limiter on the battery to prevent dead shorts from nuking the NIT, but otherwise, this ability has huge advantages.

Anywho, I'm not sure how this will work in the grand scheme of things, but it's something for you hardware geeks to think about.

i dunno about the n8x0-like devices (or the ones in the stores until 2010), but that's a industrial-scale idea... and we have the price-profit facotr on it...

hoooowever, in netbooks, next-gen NITs and such, that would be kind of a revolution... full charge in 30 minutes looks neat (i'm realistic anyway... 10 minutes is just too good)

the biggest problem with carbon nanotubes is that so far they are near impossible to build to specs.

tso: Actually, they fixed that. Someone found a way to get an incredible level of consistency to the process and they're right now working on several different battery and capacitor technologies based around it. That's why I'm expecting to be able to do the same with a NIT sized battery.
dukemagus: I did some number crunching, and your 30 minutes is just about spot on for charge time giving all the necessary factors. The even cooler part though would be to have an external charger that could pump a battery like that in like 1 minute like camera flash capacitors do.

Speaking of which, does anyone remember in the old days how capacitors used to whine when they were being charged? *raises hand* I kinda miss that. Not that the newer, silent capacitors aren't better by miles, but it was always fun hearing that low, throaty whine gradually increase in pitch until you got to that ear splittingly high pitch that singled that the flash was ready.

I have a Seiko Kinetic watch which uses a capacitor (instead of a battery) to hold a charge. The capacitor is charged by the movement of your hand during the day. I love the thing, and knowing how long capacitors can last, this thing will outlive me -- as opposed to every rechargeable battery that I've ever heard of which have either a limited number of recharge cycles or limited time from manufacture.

It was expensive, 320 USD, but it's my favorite watch and probably the best present anyone ever gave me.

Using movement for recharging like the watch does is probably impractical from a NIT perspective, but it does give one something to think about since you're pretty big on wearable PCs. Personally I wouldn't mind a small watchband attachment or even another ring if it could be used to recharge my NIT.

Joe

Edit: The watch gets about a 5 - 7 day charge from one full day (@ 10 hours) of wearing, Of course, it depends on how active your arms are, the 10 hour day thing is from general living, but I can do a 2 hour bike ride and have a pretty full charge.

something like this with a kinetic charger?
http://www.intomobile.com/2009/01/21...-bracelet.html

Good catch, tso. Yeah, something like that.

I'd have to draw the line at needing to jog 15 kilometers with a 10 kilogram suitcase-sized backpack in order to get one day's charge.

Joe.

as i've said, the cost-profit relation is still a problem

Well, I have a Casio watch and it's got a capacitor battery and charges via solar power. I only need one good day in the sun to get 2 weeks worth of charge in the battery. Even casual indoor use will give me at least a day or half a day, depending on how much light is in the room. Plus it shuts off the display to save power when you're not moving around. I'm not sure how it detects this, as I doubt, given its price, it's using an accelerometer, so I suspect it's using variations in the voltage from the solar cells to determine when you're wearing it. Either way it's a great watch. All my casios have been. Heck, I've got one casio from 1993 that's still running. Yes, it's still running, and it was my daily driver for a long time. Now I just keep it around out of curiosity to see how long the battery will last. My 2nd watch died after 7 years, but my first one is going strong at 16.