Instructables

Easy rechargable portable ipod/USB recharger

Picture of Easy rechargable portable ipod/USB recharger
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Using a USB socket, a four-cell AA battery holder, four rechargable AA batteries, and a four-AA battery charger, you can have a portable 5-volt power supply for charging or powering your Ipod or other USB-powered device.

Don't put non-rechargable batteries in the holder though, because you will wind up with 6 volts instead of five. The USB socket is supposed to supply five volts.

One nice thing about this setup is that the batteries stick together as a set of four. They get drained together, and they get charged together. Also there are no complicated circuits.
 
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Step 1: Buy a battery holder, batteries, and a charger

Picture of buy a battery holder, batteries, and a charger
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You will need a battery holder made for four AA batteries, with red and black wires coming from it. Radio shack sells these just like in the picture. Most likely, your local Hobby Store carries them too, and then you don't have to go corporate. Radio shark also sell a type which has an on/off switch, and a cover which is held shut by a screw. I don't recommend that type. You don't need a switch and you don't want to be thwarted by a screw every time you need to charge the batteries.

You can usually find a battery charger at a thrift store or in the free box at a college dorm building. Often times the charger is missing its power cord, and you can just match it up and be on your way. Buying a charger would be silly with all the free ones out there, ready to go in the trash because nobody wants them.

Most chargers charge as two sets of two (one LED for two batteries) but some charge all four cells as individuals (one LED for each battery). Those are better. Everyone deserves to be treated as an individual.

You can get rechargable batteries in a set of four. Cheap ones are 1500mAh, expensive new ones are almost 3000mAh. Get whatever is handy, and upgrade if you need to. Don't mix batteries that weren't born together, they will end up beating each other up. I am serious.
kzheng1 year ago
Um don't you realize that 4 x 1.2 = 6v
its actually 4.8v
iApple guy2 years ago
Are the pics. Copywrited?
Frowney0013 years ago
if you suppy 6 volts nothing will work. it wont charge, and it wont burn it out. my battery level of my rechargeable batteries totaled 5.5 volts for some odd reason, but nothing worked. there is a limit for usb power that should be supplied, and that is between 4.8 and 5.2 volts. anywhere outside of that, and it will simply not do ANYTHING. So don't worry about making your ipod a "Shiny coffin for burnt circuitry".
andygo4 years ago
I tried this with four 1.2v 2000mAh eneloop batteries (rechargables) to recharge my sony ericsson phones (w910i and k750i). both using the same type of usb cable. with k750i, the phone's charging indicator is activated (animating a flash on top of the battery icon), but after a few minutes, the phone's battery capacity is decreasing instead of increasing. -.-" then i tried it to charge my w910i. since this type is newer than then k750i, it shows a menu to choose what mode do i want to use? phone mode (to use the phone as a dial up 3G modem), or removable drive mode? fyi, both mode does recharge the phone. so i chose phone mode. this time, the charging indicator was not animated. but the battery capacity was instantly increased around 5% - 6%. but then it stayed the same after a few minutes. conclusion i got : it doesn't work as expected. any help? i would love to get this working. thanks! :)
ep0317 andygo3 years ago
First, you might want to implement a diode on the positive terminal of your battery bank. Make sure the color band on the diode is facing away from the batteries. This will prevent any current from going back into your battery bank and will only allow current to flow one way. Second, you need to short (connect together) the two Data pins. The way your phone's internal charging circuitry differentiates between a USB device and a USB dedicated power adapter is by checking whether the Data pins are shorted or not. If they are NOTshorted it will pull no more than 500mA..If shorted, your phone will be able to pull up to 1A (if the source can supply this).
jerkey (author)  andygo4 years ago
Dear Andygo, I think what you're encountering is that a lot of USB devices won't charge unless they see certain voltages on the DATA+ and DATA- pins of the USB socket. There are a lot of posts on the internet of people having done much experimentation on the devices that they want to charge. Much is known about the Apple products' expectations, as seen on LadyAda's site here: http://www.ladyada.net/make/mintyboost/icharge.html here's another site where people are basically discussing the problem: http://forums.ilounge.com/hacks-mods/162262-how-usb-chargers-work-so-device-knows-draw-500ma.html just google for usb charger resistors and your phone's model number, and you will find a combination of resistors to connect (to the USB socket on your battery pack) which will tell your device to charge at a reasonable rate. Please post back with whatever you discover!
whocares884 years ago
how many full charges will you get for the four batterys?
2 1/2 ithink
Thermiter4 years ago
I hate to burst your bubble, but I would not entrust my $200+ USB device to this design.  It would be a lot smarter to use 4 alkalines (6v), and a 5v voltage regulator (like the 7805) with output capacitors.  This layout is extremely variable in voltage output because of its reliance on unregulated rechargeable batteries.  You could still use rechargeables to do this, if you really care about throwing batteries away, but I would recommend using two batteries with a boost design like the Mintyboost.  It's tempting to take the easy way out when charging USB stuff, but dealing with precision devices like that is not wise, you just have to do the work.
jerkey (author)  Thermiter4 years ago
Nobody is asking you to entrust your equipment to this design. People who build it will entrust their equipment to something they have constructed, or they will choose not to. A 7805 voltage regulator has a dropout voltage of 2 volts, so attempting to get 5 volts out of one with a 6 volt power supply is not "smarter" than this design. Suggesting that such a setup would work is definitely not "wise".
You're quite right, the 7805 is not the best choice. When I built one, I used the LP3873, which has a dropout of .08 volts. I merely used it as a suggestion for a design utilizing linear voltage regulation. The best option of all is to use DC-DC step-up circuitry (like the LT1302) because of its reliability, efficiency, and low voltage requirements.
jerkey (author)  Thermiter4 years ago
Thank you for the suggestion of the LP3873 regulator. That is an excellent choice for people who choose to use this instructable with non-rechargable batteries and who are looking for precision 5.0volt output. I still believe that this instructable, with rechargable cells, is a better choice than the mintyboost. Since this circuit is electrically simple (four cells and a connector) I think that it has higher reliability and efficiency than a DC-DC step-up converter. Also, since battery chargers can hold four AA cells at a time, and the purpose of this device is to offer extra energy while traveling, I believe it is more practical than two-cell devices.
It may be more practical because it is easier to build, but it is not more efficient. At any significant current draw, say 500 mA, the average charging current of an iPhone, the batteries' collective voltage will drop below 4.8v in a relatively short amount of time, and once they go below 4.75v, the iPhone or other USB device will reject the input because it is outside of tolerance. With a DC-DC step-up, like the LT1302, the circuit will continue to give out exactly 5v until the batteries drop below Vref, which I believe is 1.25v for the LT1302. That means you will get dramatically more run time out of a DC-DC step-up than AA's alone.
yourdiyguy4 years ago
I just tested my rechargeable batts and im getting 1.45v I am guessing that would be too much for this setup? Im trying to make something similar to your setup just don want to burn anything up.
NoahM4 years ago
No offense, but you are wrong about the battery case with the ON/OFF switch. I have one, and the screw is not necessary. It is only a cover that is a little hard to put on. It's not THAT hard, though.
wat f u get a 3 AA batttery holder it would be 4.5v will that work
jerkey (author)  pancho del rancho5 years ago
While fresh non-rechargable AA batteries are 1.5 volts, they sink to about 1.3 volts when they're depleted. I haven't tried, but I don't think the Ipod will charge at such a low voltage. Besides, have you ever seen a three-pack of AA batteries? We have to stop buying so many disposable things anyway. I didn't mention this in the article, but it would be possible to safely use regular batteries in this instructable IF one placed a regular diode like a 1N400? in series with the battery pack. This diode would subtract about 0.7 volts from the total, bringing the voltage of fresh non-rechargable AA's down to a safe voltage like 5.5v. I mentioned in the article that Ipods MIGHT be okay with the full 6V but i'm not going to try it myself.
true i have a 4.5 volt regulator if i put the 1.5 batterys. also to charge a i pod dont u need to put a resistor on the left over data cables or the i pod wont charge i read it on another instructable. also i thought for any damage to inflict the i pod it had to be 4.8 to 5.2 just read that to so is that the correct voltage needed
jerkey (author)  pancho del rancho5 years ago
Thanks for mentioning the extra resistors. I will add that to my instructable.
barney_15 years ago
If you value your electronics, you need to use a voltage regulator. Please make sure to update this when you kill your device.
jerkey (author)  barney_15 years ago
actually, the great thing about this method is that you DON'T need a voltage regulator. The basic chemistry of rechargable batteries hasn't changed in many years, and they are still 1.2 to 1.25 volts nominally, which totals 5.0 volts. The USB standard is between 4.5 and 5.5 volts, and that range fits perfectly with the full-to-empty range of a set of four rechargable batteries. Thanks for cautioning readers to be careful, but I already did that.