Easy Rechargable Portable Ipod/USB Recharger





Introduction: Easy Rechargable Portable Ipod/USB Recharger

About: whats an engineer to do?

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.

Step 1: Buy a Battery Holder, Batteries, and a Charger

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.

Step 2: Find a USB Socket, or Cable

Now you need a USB socket, to provide a place for your Ipod cable or whatever cable to plug into.

The first picture is a pair of USB sockets from a desktop computer. These are a good choice because they can be found free in any computer-junk pile, and the red and black wires are already figured out for you. Don't cut off the other wires; you will need to put resistors on them later.

The second picture is a socket-end of a USB extension cable. This is the easy too, because when you cut the cable you will see the red and black wires again.

If you choose another type of USB socket, use the diagram to make sure you are getting the Plus and Minus correct. Red goes to Plus, Black goes to Minus. Make sure you don't have it wrong or you will destroy your fancy IPod. Then you can write an instructable about how to make an altoids tin out of your dead ipod (just remove dead ipod guts and add hinges).

Another option, if you have an extra IPod USB cable, is to cut the USB plug off of the cable and wire the red and black wires to the battery holder directly. If you do this with your only IPod cable, however, you will never be abe to change your music again!

Step 3: Wire Battery Holder to USB Connector

Before you start this step, put the batteries in the charger and plug it into the wall. Rechargable batteries are empty when you get them, usually, so don't skip this step. In a few hours they will be full enough to test everything.

Now you have to join the black and red wires from the battery compartment to the USB connector. Strip the wires, solder them, and tape them. Red to Red, Black to Black.

The result will be that when you put four RECHARGABLE AA batteries in the holder, you get 5 volts at the USB socket, in the correct polarity.

Step 4: Add Resistors to the Data Lines

LadyAda has discovered that many Ipods and other devices won't charge unless you put a couple of resistors to the other two USB wires. Fortunately you did not cut off those other two wires (they are probably white and green).

Get a pair of 100K ohm resistors (brown black yellow something, or brown black black orange something) and twist them together at one end. Connect that end to the red wires. The other end of each of the resistors goes each of the remaining wires from the USB socket.

You are basically connecting one 100K resistor between VBUS +5VDC and Data+,
and another resistor between VBUS +5VDC and Data-.

The second image is from the Mintyboost version 1.2, and is for reference purposes only. Ignore the right half of the screen. Ignore the fact that the resistors do not exactly connect to +5VDC in that schematic. If you want to make a mintyboost though, use that schematic.

For more information about the Mintyboost, see the Mintyboost 1.2 FAQ:

Step 5: Use It!

All you have to do now is put it together. Put the CHARGED batteries into the battery holder, and confirm that the polarity is right on the socket - you can do this using a USB laser mouse that lights up when its on, or a USB hub that has an LED on it. That way, if you have it backwards or otherwise wrong, you don't risk turning your ipod into a thiefbait paperweight.

A hot-glue gun is the correct way to stick the USB socket to the battery holder once you're sure everything is done right. Make sure you don't get hotglue into the holes of the battery box where they will block the batteries from contacting their terminals.

Now would be a good time to put an easy-to-read warning sticker on your battery holder that says, "DO NOT PUT NON-RECHARGABLE BATTERIES IN HERE OR DAMAGE MAY RESULT!"
This is because non-rechargable batteries are 1.5 volts, which would total SIX volts - more than USB is supposed to supply. Probably the IPod would be okay with this, but no guarantees that it won't turn your IPod into a shiny coffin for burnt circuitry.

That's it! Hopefully the Ipod will continue to charge until the battery pack totals 4.0-4.4v and then stop. At that point it is time to charge the batteries the next time you get the chance. Unplug the Ipod from this device when you're not using it, so that it doesn't keep trying to charge the Ipod after it's full.



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    24 Discussions

    is there any weay to do this using a DR35 battery?

    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! :)

    3 replies

    Use rectifier diode and btw
    Make charging circuit so you don't overload the battery
    Put rectifier both on power input and for the power after switch , it'll be better and data line green + 148K
    Data - 100K resistance , works the best like that

    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).

    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!


    5 years ago

    Um don't you realize that 4 x 1.2 = 6v

    1 reply

    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".

    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.

    4 replies

    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.

    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.

    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.

    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.

    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.