(yet Another) IPhone Charger




I've seen quite a few, but being a road warrior, space/size and weight are paramount to me. And finding a 9 volt battery is pretty easy.

I originally made this for my old Palms.  With a few resistors it works for the iPhone.

Simple design.  A DB-9 hood with the ears cut off as the case, the ubiquitous 7805 as the regulator and a 9volt battery connector.  (I used one from an old battery, its stiffer then the ones you would buy at Da Shack)  Granted the 7805 is far from efficient, but it works and keeps the whole thing small and easy to build.

Parts list:
7805 5 volt positive regulator
100K SMT resistor (2 pieces) Size 2012
20K SMT resistor (1 piece.  I didn't have a 20K but used a 10K) Size 2012
USB female connector  (I gutted a device to get mine)
9 volt battery connector (I got mine from an old battery, worked best for me, plus its less in the landfill)
DB 9 hood  plastic for easier modifications

Wire, solder, heat shrink, potting compound (optional)
Wire cutters/strippers
Rat tail file
Dremel  (though I used a milling machine, a bit overkill)
Soldering iron  (hot air SMT with paste works best, but I didn't dig up that stuff for such a small project)
ex-acto knife

On with the show!

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Step 1:

Gather your stuff.  I didn't take pics of tools (should I?)

The USB connector:

Pre solder the pins for soldering the SMT resistors.  I did it far from the end as not to unsolder it when soldering on the wires later.  I also snapped off the PCB mounting lugs

Step 2:

Solder on the resistors.  A good set of tweezers will help a lot.  I have a pair that when squeezed, they open; so they naturally hold an item.  I tacked one side then the other.  The fun part is holding them level on the pins.  Don't touch the resistors with the iron, just the pins of the USB connector and let the molten solder do its work flowing over the end of the resistors.

The order as seen left to right.
100K  20K and 100K

(remember I used a 10K, but I suggest keeping with the 20K)

Once done, you should test it.  With a DMM on ohms, test between pins 1 & 4 and it should be 220K +/- the cumulative tolerance of the 3 resistors.  If not, then something is amiss. Wrong resistors or bad solder joint.

Step 3:

File, if needed, the heat sink of the 7805 to fit between the screw posts of the DB 9
I used a rat tail file. 

Just a note.  Its copper (thuogh some might be aluminum) so it will clog the file quickly, have a file card handy to clean the file.

Step 4:

Trim down the 9 volt connector to fit correctly in the DB 9 hood.  Rubbing on a sandpaper or a file works nicely.  Remove evenly from both sides.

Also trim out the cable end of the hood to fit the USB connector.  A file or heated ex-acto blade works well.  Dremel can work too,  just need to square up the corners afterwards.
Dremel will work well for cutting off the ears too.

Go slowly with each and keep testing for best fit.  A little 'grab' from the hood helps to keep things in place if not using potting compound.

Step 5:

Solder up the 9 volt connector to the 7805.
Trim down pins 1 & 2 of the 7805 and bend back pin 3.

Pin 1 is the 9 volts into the 7805
Pin 2 is the negitive (common or 0 volt or ground take your pick of nomenclature)
Pin 3 is the 5VDC out

Now add the heat shrink tubing to the wires and solder up to the USB connector
USB pin 1 = 5DVC
USB pin 4 = GND

Shrink the tubing over the USB connections and pin 3 of the 7805

Step 6:

Add some heat shrink tubbing to pin 2 & 3 separately and bend over if in the way.

Stuff the guts into the hood and close up.
At this point you can fill the cavity with potting compound.

(If using JB weld, epoxy or other makeshift potting compounds test to make sure it doesn't conduct electricity when its dry/cured!! )

Charge away!

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    34 Discussions


    4 years ago

    So just to be clear it can't charge an iphone 5?


    5 years ago on Introduction

    what iPhone does the author have? my iPhone 4 doesn't charge, but my iPod t 2 does, but it was made pre-revisessd apple charging standards update( which is the point of the resistors) ?

    well.. project semi complete. my iphone only told me to restore it on my computer. i tested the leads with my dmm and i have a 5v DC current with .58 amps. WHY DOES IT DO THIS? i plugged a ps3 controller into it and nothing happened. WHAT IS WRONG?!? I NEED THIS DONE BY TOMORROW!!! (and nothing is shorting it out, im not that dumb)

    2 replies

    ps3 controllers dont charge the same as other usb stuff, but neither does iPhones. but ps3 controllers has a totally unique way of charging, nothing should charge those except a ps3. so you can't use that to analyze your results.

    i think your amperage is a lil too lean there .. or too much.. check the specs online for the milliamps that those devices can tolerate


    6 years ago

    This won't charge any newer apple devices iPod touch 3rd+, iPhones the data pins need 2volts each


    6 years ago on Step 5

    But dont the 2 & 3 pin on the usb need 2 volt for to work with iphone

    1 reply

    7 years ago on Step 6

    I'm curious as to how many 9v batteries it will take to charge a dead iphone 4? Great article!


    Actually this does not work for the iPhone 3GS because it draws 1 amp. Obviously a problem. Ladyada Who made the minty boost and that somehow takes .5 amps and makes the iPhone charge... Magic?.. I'm starting to think so. Haha.

    1 reply

    8 years ago on Step 2

    what is the significant difference between a 20k and a 10k resister? all the shack had was 10k resistors.

    1 reply