How-to Make A ‘usb Battery’

usb battery

found out yesterday that there’s a shuffle shortage and gadget battery life can only be expected to get worse.  bummer.  at least you can make the most of your waiting-for-shuffle blues and solder yourself a ‘usb battery’.  this little gizmo runs off a 9 volt battery and supplies your favorite little device with the proper 5 volts of mobile power.

in lieu of running an ipod off of it, i tested it with an mpx220 smartphone and it should work fine with any low power mobile device that can charge via usb cable.  read more for instructions on how to make your own.

here’s what you need to scrounge up:

  • 5.1v zener diode.

  • 100ohm or slightly greater resistor.  all i had was a 330ohm which works.  don’t try anything lower than 100ohm.

  • 9v battery connector and 9v battery.

  • flat female usb connector that mates with your device’s usb cable.  this is the hardest part to find.  i tore mine off an old usb extension cable.

wire it up
usb battery wiring

connect everything up as shown.  a board makes it easy, but in a pinch you could just wrap ends together.  the top two wires go to the battery and the bottom two are connected to the female half of the usb cable i butchered.  polarity matters on the diode, so check your work.

test it
usb battery voltage check
connect the battery and test the voltage over the diode.  it should be close to 5 volts.  if not, make sure you have everything wired correctly (pay special attention to the polarity of the diode).

try it
usb battery mpx220 test

still waiting for an ipod, i decided to grab my smartphone and kick the tires on the usb battery.  as you can see in the image, the device thinks it’s plugged in.  you should be able to use any low power device that charges via usb.

how it works

the zener diode conducts in the reverse direction when its breakdown voltage of 5.1 volts is reached, and the voltage across the diode will be that same 5.1 volts, so it acts to limit our 9 volt supply down to roughly 5 volts, which is what usb powers devices at.

the resistor is there to keep the circuit from shorting when the load (your shuffle) is removed.  if you use a resistor less than 100 ohms you’ll know it because it will get hot.  if you use too large a resistor, you won’t be able to supply enough current to your device.

finish the job
usb battery solder
as you can see, i’m pretty nasty at soldering.  i’m under strict orders from cl to keep this tiny and pocket sized for the ipod, so i’ve tried to cram everything as tight as possible.  as soon as minneapolis warms up enough for the ipods to migrate, i’ll be making a custom case for this.

till then, please send in your comments, ideas, and hacks.  i look forward to seeing what you come up with.

186 thoughts on “How-to Make A ‘usb Battery’

  1. Technically, a usb cable can carry more then 5 volts. I have been able to send 30v thru one. The USB standard requires that usb run on 5 volts. Everyone go read the new article “USB-Battery 2.0” and check the back logs of hacks. They have a couple of 12v firewire iPod battery packs in mind.

  2. ok idia but I would not! risk my ipod on a znier diode converter but on firewire( if they are the ieee 1394 specs say the device (ipod) shoud
    be able to accept 7-24 volts without “smoking” to be ieee1394 (firewire) complient.

    infact one cool thing about the “big” and mini ipods is that they have a buck/boost
    (step down/step up) dc-dc converter….

    the charger that came with my ipod is a swiching psu rated at 12 volts 1amp

    in the my shuffel therey , no responablity to damige …..because the ipod uses 2 aaa = 3.0volts but
    usb is 5.0 volts there allredy is a dc-dc converter of some kind!!!

  3. has anyone tired to charge their ipod shuffle using this method or the other one, i have and it does not charge, i think it runs off it instead. as there is no data communcation with had.


  4. This is overly complex circuitry.

    Use 4x AAA alkaline cells (about the same net size as the 9V battery), you can get a 4 cell holder with solder tabs at Radio Shack. Cut one end off a USB extension cable. Put a silicon diode in series with one lead, which will drop the 6V nominal battery voltage to approx 5.3 Volts. Works fine for loads within the current carrying ability of the diode. No wasted power (heat) through a dropping resistor, very little diode heating. When connected device is off, no current draw at all.

  5. I just saw this:

    Product News Network, Jan 5, 2005 American Power Conversion(APC) USB Battery Extender — allows up to 60 minutes of talk time via a USB charging port. Use and charge a mobile phone. This small, compact power solution is the perfect emergency battery. Requires a USB charging cable and AAA batteries — cable sold separately. (Estimated resale price of $7.99).

    A lot easier than DIY

  6. I recently purchased (unfortunatly I didn’t have the nerve to make my own) a cmoy amplifier on ebay. It occured to me that this cool little usb battery device could be applied (in reverse) to power the cmoy from your usb hub. So that I can power the cmoy indefinately through the computer (which is where I usually use it). Does anyone have any suggestions how to go about this? What would I need to regulate the power from the usb port? The cmoy can run on any regulated power supply unit ranging from 300mA up to 1000mA 9v -12v

  7. lowercaseness is in the CSS file, in case anyone cares.

    body {
    color: #eee;
    background: #000;
    font-family: Arial, Helvetica, Helve, Sans-serif;
    font-size: small;
    padding: 0 0 8px 0;
    margin: 0;
    border: 0;
    text-transform: lowercase;

  8. ok, im a newbie but i built both usb battery, this one and the onther in this site.

    this one are strange. when i test withmy meter i got 5.14v, but when i try connect any device (ipaq or ipod) nothing happens.

    anyone here had the same problem and know how to fix it??
    thanks in advance


  9. i would sudjest to encase the usb cirtury in hot glue so it Is more stable/sturdy you do not close of the cable acces. and if you do make sure that you don’t restrict the use of the usb slot.

  10. i would sudjest to encase the usb cirtury in hot glue so it Is more stable/sturdy you do not close of the cable acces. and if you do make sure that you don’t restrict the use of the usb slot.

  11. An excelent hack for a quick fix for ipods, laptops and many other items similar.

    What you would do is hack the shuffle case so it can accomidate one of theese sets (battery included) INTERNALLY with the battery poking out a bit ala gameboy.

    Pretty useless at first glance but undeniably good for keeping in your hackbox.

  12. yo thats phat!!! does it work in a ac cirquit??
    like if i get my old nokia charger and slam it on the floor ’till it opens then buy some diodes and resistors to make 5 volts come out of it, will it work? and if so, what kind of diode and resistor will i need?

  13. Found a dps-9000 external battery at 7.2 volts for my PDA. since the internal battery is 3.6v but the PS is 5 volts I am afraid to push it to 7.2. Like the use of the 7805 to get down to 5 volts which also works on my digicam.But from looking at the data sheet it looks like it needs a larger power drop then 2.2 volts. Would it in fact work at that input voltage?

  14. Found a dps-9000 external battery at 7.2 volts for my PDA. since the internal battery is 3.6v but the PS is 5 volts I am afraid to push it to 7.2. Like the use of the 7805 to get down to 5 volts which also works on my digicam.But from looking at the data sheet it looks like it needs a larger power drop then 2.2 volts. Would it in fact work at that input voltage?

  15. If you do not supply enough voltage to the 7805 then it will output less than 5 volts. How much less depends on the cuttent being drawn. Going by memory, when I tried it 10 years ago, the more current the bigger the voltage drop. At low current I believe it was a little over 2 volts, but at an amp it was about 3 volts. So, you need a little over 7 volts input at low cuttent and at least 8 volts for 1 amp.

  16. just an idea instead of useing a battery you cam use other things like a solar panle. I found that the lego or knex ones work the best. Calculator ones not so good. Or you can just use the hamster setup in which case you need:

    a hungery hamster
    hamster food(mine likes karots)
    a modded hamster wheel(ie hamster wheel with moter attached, gears can be attached to increase production)

  17. I built something similar, just added some capacitors to buffer voltage peaks in case they occur. My device can be used as a “Battery Pack” or as a usual charger. I don’t know why the iPod shuffle only starts charging after switching the input voltage beneath that one required by the 7805 to work correctly und back up again. Seems the Charge mode has to be activated in some way.

  18. i have a usb2 pccard, i made a batter back to plug into it instead of an ac adapter, cause i want to be able to use it away from ac. but the power connector is bent inside or something and is intermitent, i cant trust it. my battery back is 4 nimh 1.2v batteries equaling(1.2*4) 4.8. which seemed to do fine for the device i was trying to power. so my question: can i make a usb cable that cuts off the power from the host, then connect to my batter pack to supply 4.8 volt to the device.

  19. in reply to all ipod users, specially to jj: yes, seems like charge mode has to be activated. i do so by driving +2,8v on the d- usb-pin (the one next to +5v usb-pin) with a voltage divider formed by a 215k and a 274k resistor supplied by the +5v in a 7805 based design with caps on in- & output. have fun, tom

  20. Thanks for the hint! Do you know if it’s necessary to permanantly have those 2.8 Volts on the D-Pin, or if a single impulse is sufficient to activate charge mode? If so, one could add a switch to toggle between “Battery Pack” and “Charge” mode?

  21. You dont have to use the zener regulator. You could just power it directly off the 9 volt because the iPod is rated 5-30 volts DC 1A max. It says it on the back of the iPod in the engraved stuff below the serial number.

  22. you are certainly not speaking about the ipod shuffle! There is no such information on it, and i doubt that it can be powered with more than +5V without being damaged immediately. try it out and post pics, and not just fairy tales…

  23. yeah ive seen something like tihis excpet they used 3 9volts and threw it in an altoids tin after they cut a hole for the usb adapter i have not tried it but i say some photos looked easy

  24. Response to post #82 Tom. I thought you had to have both pull-up and pull-down resistors on the d- and d+ lines. Are you leaving the d+ line float? Does your Ipod charge at the 100ma or the 500ma rate?

  25. If i were to create an equivalent version of this for a nokia phone without the usb setup (most all nokia’s require 3.7v), how could I drop the voltage to 3.7? the best i could think of would be to use a lm7805 as mentioned above, as well as a resistor of some sort to drop it even more. however, this raises the problem which wasnt adressed above of battery depletion. once it loses voltage, how do you maintain that constant 3.7ish?

  26. So I need to make one of these, but need to use 4 AA batteries. I know that using a 7805 won’t work because 4 AA do not equal the 7 volts required for the 7805 to successfuly regulate down to 5volts.

    What should I use instead of the 7805 to get the 6 volts generated by the 4 AA down to 5 volts? Silicon diode? Something else?

  27. I made this and i thought it was going to work. it seems pretty simple but instead of charging my ipod it takes the batter away. where does it go and how do i fix it.

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