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You realize, don't you, that battery is a plural term already?

Says who? Check out the title of this webpage. http://www.duracell.com/en-US/index.jspx

Google doesn't try to correct me when I search for batteries either. Even MW doesn't have a problem with the word.

batteries. (2010). In Merriam-Webster Online Dictionary.
Retrieved January 30, 2010, from http://www.merriam-webster.com/dictionary/batteries

Duracell has invested millions of dollars in wireless power transmitters. These transmitters are about two and a half inches long (6.33 centimeters). One of the transmitters can put out 10 watt-hours, while another type can be daisy-chained to easily produce over 100 volts.

They're constantly improving the technology; Units are usually at least 75%-85% efficient. And they are not affected by the inverse-square law. It's pretty interesting stuff.

Just not 'air' ones.
http://www.duracell.com/Procell/chemistries/lithium.asp

I knew it all along.

Well if you want to know what is in a Duracell look here.

Duracell.com

Alkaline Manganese Dioxide is what is used. The cheap batteries are made from zinc-carbon.

But there's also some amazing, non-experimental, stuff being done here and here. They've been doing "Wireless power" for many decades...

as regards the "couple of D-cell batteries hooked up to the motherboard" you suggested, they wouldn't have nearly enough power output to run most systems. According to the specs, http://duracell.com/oem/Pdf/new/1300_US_Ultra.pdf a D cell battery can provide a max of 2 Watts, and can only hold that load for about 90 minutes. Assuming your system has a power drain of 200W, (relatively low) you'd need 50 batteries to keep your system going, much more complicated than using a UPS. You don't want to run your system with less power than it needs, as this could be potentially damaging to the processor. If it's that important that you shut down properly in the event of a loss of power, you should just hook up a small UPS with adequate power output

Actually, I've seen a lot of EEs do the same thing, with no more understanding than the basic voltage drop analysis. You have to keep in mind that an engineering degree confers exactly the *opposite* thing to the practical knowledge required in the real world. Those people who make good engineers already got their practical knowledge from playing with Lego and hacking their bicycle.

You see, the reason why a D cell is bigger than a C cell is bigger than a AA cell is bigger than a AAA cell despite all putting out ~1.5V is because of current capacity. A modern D cell will put out 1.5V into a 1A load for many (~15) hours, while a modern AAA cell will put out 1.5V into a 1A load for around an hour and ten minutes.

Trivia question: why is there AA, AAA, C and D but no A or B? Answer: The A battery was a big 1.5V lantern battery used to heat the filaments in radios before rectifier tubes were practical to allow the radio to be plugged in to a regular outlet, and the B battery was a 30V, 45V or 90V battery used to provide the plate voltages for the tubes in these radios. The B battery stuck around until the early transistor radios of the late 1950s replaced all the tube portables. You can actually still buy both battery types but generally only through big electronic parts suppliers.

(Quoting Duracell's alkaline battery data sheets, difficult to link directly to the PDF so click on "Technical Bulletin" and scroll to page 9/13, D cell 15Ah (15,000mAh) and AAA cell 1.15Ah (1,150mAh).)

Go to Radio Shack and buy a multimeter. Stick it in current mode, and measure the current consumed by the iPod. Then look up the mAh (milliamp-hour) ratings for the type of battery you wish to use - NiMH, Energizer Lithium, Duracells, whatever. Do not mix battery types (brands, chemistries, etc), ages (new batteries and old batteries should never be put together in series), or sizes (AA, 9V, D-cells, etc.) because you will have some discharge faster than others, sometimes to the point of actually trying to "recharge" the weakest cells off the strongest cells.

Figure out which battery size you need to use based on whatever you consider to be an acceptable battery life for long trips, and use it. Of course, there will be design trade-offs in order to achieve a reasonable size - shorter battery life or bigger and heavier batteries - some compromise will probably have to be reached. If all you care about is battery life, for example, just stick the iPod directly across a car battery.

Get appropriate sized battery holders at Radio Shack or any number of electronic parts places - MCM Electronics, All Electronics, Digikey, Newark, Electrosonic, etc. Connect them in series and build them into a plastic or aluminum box, properly secured and screwed down. Use heat shrink tubing instead of electrical tape for all connections, and use a grommet (those little plastic things where the power cord enters your kettle or toaster or whatever) to prevent the wires getting frayed.

And, most importantly, once you know the current the iPod consumes, multiply that number by two and buy a fuse with that rating. Put it in a holder in the battery box - that way, if the power cord to the iPod gets caught and damaged, or if the iPod fails catastrophically - there won't be a fire.

We've never been told explicitly how they get the bioelectic energy out of us, efferectivly transforming us into this this [duracell.com]

I just hope the machines don't get all uppity and decide to convert a human being into this.

...if only the machines had used the humans for data storage!
Morpheus coulda pointed to a SAN/NAS box!

Instead they make a duracell commercial and mumble about the "human body generating more bio-electricity than a 120-volt battery and over 25,000 BTUs of body heat."

Ok I'll quit ze bitching... it was spiffy anyway.

Nokia obviously wants me to buy a new phone- but mine is perfectly good, except for want of a 35-cent part with some additional metal bits attached.

I'm a little confused... didn't you just point us to the battery that you need?

The link that you referenced points to the DL2025 Duracell battery. If this really is the battery that you want, they are pretty darn common.

Quoting from the article (emphasis mine):

The unit uses a NiMH battery which means that there may be a memory problem so make sure it has a good first charge. Once and awhile it is good to totally drain the battery and recharge it totally, this is called refreshing.

NiMH rechargeable batteries have a negligible memory effect (the correct technical term would be voltage depression). References:

Duracell (HTML)
Duracell (PDF, more exhaustive)
Energizer (search for voltage depression)
Greenbatteries

My experience is that most so-called memory effect problems with NiCd and NiMH rechargeables can be traced back to cheap charger units which overcharge the batteries. Use a microprocessor controlled charger whenever possible, it may be a little more expensive at first but it will save you trouble in the long run.

Quoting from the article (emphasis mine):

The unit uses a NiMH battery which means that there may be a memory problem so make sure it has a good first charge. Once and awhile it is good to totally drain the battery and recharge it totally, this is called refreshing.

NiMH rechargeable batteries have a negligible memory effect (the correct technical term would be voltage depression). References:

Duracell (HTML)
Duracell (PDF, more exhaustive)
Energizer (search for voltage depression)
Greenbatteries

My experience is that most so-called memory effect problems with NiCd and NiMH rechargeables can be traced back to cheap charger units which overcharge the batteries. Use a microprocessor controlled charger whenever possible, it may be a little more expensive at first but it will save you trouble in the long run.

Ok, so I've gotten into this geocaching thing lately, and while working on a cache to be hidden in about 60 feet of water off the coast, it occured to me that a blinking LED might make it easier for divers to spot. No problem, whip up a blinker circuit with an LM3909 and a super-bright green LED and we're set. But what about power? Sure, four D-cells would let it run for close to a decade, but where's the fun in that? The undersea environment is quite dynamic, and there's got to be some power down there that can be harnessed. What I need are some ideas on how to do that.

We keep seeing stories here about tidal power, and that's cool, but I don't see how it can be done without a column rising all the way to the surface. So here are the ideas I've got right now. Keep in mind that the device will probably be housed in a length of 4-inch PVC or ABS pipe, and it needs about 0.5 ma at 1.5 volts:

• Surge power. Put a couple of funnels back-to-back with a CPU cooling fan-sized turbine and generator in the middle, and run the output through a rectifier and capacitor. But how reliable will those moving parts be after years underwater?
• Self-winding watch concept. Float the thing tethered to the bottom and install some sort of pendulum inside with a magnet on it, moving through a coil. The moving parts are protected, but will it be enough power?
• Yank the chain. Again, tether it, but use the varying tension on the tether to drive a dynamo of some sort.
• Nukes. Anyone got a spare radioisotope thermoelectric generator? Any idea how many smoke detectors I'd need to cannibalize to get enough Americium-241?
• Magnetohydrodynamic generator. Like the surge power thing, but using the flow of cunductive seawater through a magnetic field to generate a current. I have no idea how much power this would generate, if any, or how to deal with ion accumulation at the electrodes.

The generator need not fit inside the 4-inch cache tube, but it shouldn't be huge, either. It needs to be practical to build, and not terribly expensive. Above all it's got to be reliable and enduring. Any ideas?