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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."
explaining your stack of batteries when it shows up on the x-ray at an airport. ;)
We want solar iPod now!
placing two cells in parallel can mean that one will discharge through the other - a stack of 6 or 8 AA cells in series would be better
I still get 12 hours of play out of an old CD player(11 years old), from too AA batteries. I havent seen anything recently which managed this.
All the recent CD players I have seen last 4 hours but have 1 Meg buffers, 2x read speed, feature, feature etc.
I'm sticking with my old CD player, It works as I want and has the only features I need (long battery life).
As I do, if you've ever taken it apart you'll notice there is quite a bit of space left in there. The battery is quite thin. I've often wondered if you could just buy another battery from say www.ipodbattery.com and install it internally, coupled in parallel with the original one. (same voltage, twice the capacity) Any EE's could verify if this would work?
I have been using an old Sony MD player for quite a while. On one (count 'em, ONE) AA battery I routinely get about 30-35 hours playback at moderate volume. I have never used any music player that even comes close to this.
6 pin Firewire pin assignment (& others)
;)
Need to know which ones are the power pins, right?
Anonymous Joe
on the downside, they currently have no remote and cant work as a USB harddrive without the use of additional software. fortunately, rio are constantly updating the player with new features, and are in the process of making it work as a usb harddrive.
Minidiscs are alright (i own a sony N10 [top model]). It depends what you like though. They do have great battery life, but this is at the expensive of the amp.. so thanks to their weak amps, the sound quality isn't great. they're really good for the average joe, who (shock horror) uses the stock earbuds, and is happy with things like 128kbps mp3.. but as a music fan the weak amp annoys me (which is why i'm buying a karma, and have just built a portable amp)
In the first picture, there are a GP and a Varta 9V battery in parallel, with at least two cells, at least one of which is rechargable. So, 9 + (2 x 1.2) = 11.4 V.
In the second picture, there are two Varta 9V primary batteries in parallel, placed in series with two 1.5V Duracell alkalines. So, 9 + (2 x 1.5) = 12 V.
We can assume the difference in non-load voltage is not relevant. But when we consider the power available:
The capacity of each PP9 Varta is at most 450 mAh. (Rechargables are 110 mAh to 150 mAh). Taking the best case in parallel, therefore, 900 mAh. The rechargable AA's are about 1350 to 2300 mAh. If primary AA's are used, then figure on 2400 mAh.
So for an all-primary solution, the AA cells have 2.5 times the life of the PP9 cells. Basically, this design eats PP9 cells and there's no real way of telling which batteries/cells are running out at any given moment.
If one's going to go for a primary cell solution, then it would be better to have, say, 3 x 2CR5 in series or 3 x CR-P2 in series. But obviously a rechargable pack is the optimal solution because it's way cheaper in the long run. Buy them all together, Use them together, recharge them together. Check out packs used for digital cameras.
The first problem with the battery pack is that it is grossly unbalanced. He shows alkaline batteries in it, so let's cruise on over to www.energizer.com and get some specs. A 9V Energizer has 625mah while AA Energizers have 2850mah capacity. Parallel the two 9V and you are only up to 1250mah, which means that the two 9V batteries will be dead before the AA cells are even half of the way used up.
Next, he is using expensive and environmentally harmful alkaline batteries rather than NiMH rechargeables. According to the EPA, Americans throw away 2 billion non-rechargeable batteries per year -- almost all of which end up in landfills. The single largest source of mercury in garbage is alkaline and button cell batteries. He took an iPod that had a battery pack that could be recharged for about a year and a half and made an alkaline pack that has to be thrown away every ten hours! It's projects like the one described here that make me think that the feds should ban all non-rechargeable batteries bigger than button cells.
Since the iPod would run on anything from 8-30V, he would have been a lot smarter to use 8 AA NiMH batteries in a case like this or this.
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.
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.
I'm still waiting for plans for a homemade Belkin battery pack.
The difference?
The belkin packs, as you may have noticed, use only 4x1.5V. They don't charge the iPod battery, they power the iPod, getting 15-20 more hours of playtime, a better solution to me. This is probably done by jumping a pin in the proprietary dock connector of the iPod.
If someone could figure out which pin to jump or otherwise how to make this, it would be a wonderful solution.
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.