Slashdot Mirror
Build Your Own iPod Battery
OmniVector writes "With various complaints about the iPod battery's life, and its mere 10-8 hours of charge many of us are left looking for a way to keep the tunes kicking a little longer. Drew Perry has come up with a novel solution which can only run you a few bucks for an extra 10 hours of battery life out of a box of playing cards and a everyday batteries. Not bad for that long car trip where you just don't have a firewire charger handy."
batteries are a known quantum in the world of travel security. scanners are designed to know what they are and how they're used.
...
contrary to popular belief, batteries do not look like explosive devices.
this diy-playing-card-battery-charger might raise a few eyebrows for its 'concealment' factor, but then, you don't have to use a playing-card box. you could just as easily use something else that actually looks like a plastic case designed for carrying batteries.
this is a clever hack, anyway. the schematics are where the value is - whats the bet it won't be long before you can get these plastic cases in the akihabra back-streets, selling as 'cheap firewire-device rechargers' or whatever
; -- the corruption of government starts with its secrets. a truly free people keep no secrets. --
THIS IS NOT SAFE!
There are 2 x 1.5 volt cells in series
And 2 x 9 volt cells in parallel
I know for certain this causes heat problems during charging or discharging because of the charge inbalance between the cells.
This could lead to explosions in extreem cases.
If you need to build one, I would suggest removing one of the 9 volt cells or adding 2 more 1.5 volt cells in parallel
Buy a 40-hour iPod battery for $100 bucks.
That's Right. 40
6 pin Firewire pin assignment (& others)
;)
Need to know which ones are the power pins, right?
Anonymous Joe
Ehh...yeah...and I noticed he's got different brands of batteries and even chargeables, standard, and alkaline batteries all mixed together. That's quite a little cocktail of things that can go wrong. Once that dry cell nine volt dies and the alkaline hasn't yet, the circuit isn't so hot any more...or maybe it is hot, in a bad way.
Just get 10 NiMH AAA batteries and wire them in series. They're 1.2 volts, so you'll get 12 to start off. It'll end up being about 1.75"x1.875"x.75" if you don't use holders, otherwise you can use two 4-cell holders and one 2-cell holder in a small box, which would make it a lot easier to pull out the batteries for recharging. This gets you about 600 extra milliamps, I have no idea what the iPod drains. If you used AAs instead, that would get you up to 1800ma. But 10 AAs are a little heavier.
Might as well go for the 12 volt lantern battery!
...
Instead, either use two 4-way AA cell holders in series with non-rechargeable cells(for a total of 12V), which are available from most electronics distributors, or a combination of 2 and 4 way holders to allow the use of 10 NiCd or NiMH AA or AAA cells - also for a total of 12V since these cells run about 1.2V each. With a diode and a resistor you can trickle charge this arrangement through a car lighter plug, since car batteries run around 14.5V. It's a kludge but a feasible kludge.
I wonder if anyone has looked at modifying the works of a Freeplay radio (wind up dynamo) to act as a charger for small appliances like iPods?
Panurge has posted for the last time. Thanks for the positive moderations.
Backup battery pack
LotD
I'm assuming he chose this configuration because a 9V will discharge faster at a given current than a AA.
He chose this configuration only because he was trying to be clever and fit it into a playing-card pack.
As to what you're assuming - no. Battery voltage is determined by the chemical type of the battery. Size doesn't matter. So for example, standard alkaline AA, AAA, C, and D batteries all put out 1.5V, but Ni-Cads put out 1.2V. Lead-acid like your car battery is 2V.
Therefore, a 9V battery is just six tiny 1.5V batteries in series. Get some tin snips or whatever, and carefully cut open the outer casing on a 9V and you can see for yourself.
Also, you *can* safely run batteries in parallel. The only gotcha is that you can run into problems if you try to charge the batteries in that configuration when they are not evenly discharged. His picture looks like he isn't using rechargeable batteries, though. Or if you had rechargeables, you could pop the batteries out and charge them individually.
Personally I think it'd be more straightforward to just wire up 8 AAA batteries in series and forget the 9V nonsense. Probably would get longer battery life too. I don't know if they'd fit in a playing-card pack, but they wouldn't be much larger.
Most of them are very concerned about things ending up in the trash which are not supposed to be in the trash, and are quite helpful when questioned.
Its a helluva lot easier to help someone properly dispose of something than it is to try to recover it out of the landfill once its presence has been detected.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
I'm pretty sure Radio Shack will take your used alkaline batteries. Or any electronics store for that matter.
I would suggest that anyone carrying extra batteries for a personal device, put them into the change cup.
I've said it before, and I'll say it again...
What highjacked those planes was not box cutters, but fear, weak doors and historial compliance to anyone. The Heroes of Flight 93 showed what really happens in the "new reality".
The grass is only greener, if you don't take care of your own lawn.
Recyclable batteries do not last nearly as long as non-recyclables... at least the ones I use.
The better NiMH AA-size rechargeable batteries are rated at 2100-2200mah. An alkaline AA Energizer is rated 2850mah, meaning that it has about 1.3x the capacity. But there is more to it than that. NiMH batteries work far better than alkaline batteries in power intensive applications. A NiMH battery maintains a high and consistent voltage during most of its discharge. An alkaline battery's voltage drops rapidly when used in a power intensive applications such as digital camera. In that kind of application, the NiMH batteries last far longer than alkalines.
Where alkalines have a big advantage is in things like smoke detectors and remote controls. A NiMH battery will "self-discharge" in 1-2 months while an alkaline battery will last for years with no load.
Also, be careful not to confuse NiCads with NiMH batteries. The two are drastically different in capacity. A typical AA NiCad has a capacity of 700mah, 1/3 the capacity of a modern AA NiMH cell.
To be blunt, this design isn't so bright... Sure, it produces a reasonable voltage, but it's not a good idea to mix different types / sizes of battery in this way. If batteries are mixed in parallel like the PP3 batteries in this circuit, large currents may flow from one of the batteries to the other - it's unlikely both batteries would output exactly the same voltage. If batteries of different sizes are mixed in series, one type may discharge before the other. The discharged cell may potentially be reversed - i.e. current will flow through it backwards. Either of these situations may cause the batteries to vent gas, overheat, or if safeguards fail they may even potentially explode. This is the sort of thing that you may get away with for some of the time, and you may not see any problems immediately - but in the long term you may well burn your house down. This advice comes from experience. If you short a rechargeable battery you can draw extremely high currents (even 10s of amps) and start fires very quickly. I once melted a long piece of plastic insulation very quickly when two contacts touched at the end of a battery lead. The battery got very hot - I burned my fingers trying to disconnect it. Treat batteries with respect. I'd be willing to wager that electronics kills many more people through fire than electrocution.
It's obviously not the work of a professional engineer, but that's what makes it neat. Taking a just barely functional knowledge of what's going on and solving a problem using available tools. I suspect this guy isn't going to be the professional EE you all think he should be for at least 4 more years
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.
Fire and Meat. Yummy.
When I fly I carry all kinds of change, several AA's, tokens, pens & what not. To get around having to haul all this stuff out for inspection all the time (esp for connecting flights) I usually carry a ziplock bag or two and stuff anything that might remotely go into the change box. One item, no fussing & my pockets are lighter.
"Sanity is not statistical", George Orwell, "1984"