Introduction: How to Make Your Own USB Car Charger for Any IPod or Other Devices That Charge Via USB

Picture of How to Make Your Own USB Car Charger for Any IPod or Other Devices That Charge Via USB

Create a USB car charger for any iPod or other Device that Charges Via USB by splicing together a car adapter that outputs 5v and USB Female plug. The most important part of this project is to make sure that the output your chosen car adapter is between 4.75v and 5.25v otherwise you risk damaging your device. Please verify voltage with a voltmeter.

Step 1: Introduction

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Note: I have tested this only on an iPod Nano, but I would imagine that It would work for any iPod that charges via USB, or any device that charges over USB that uses a 5v source for charge.

The basic idea here is to charge my Nano via USB while in the car. The total project cost for me was Free-99. I had all the spare wiring and cables because I never throw anything electronic away. I did however build another one for a shade under $8 bucks. I mean thats not terrible for a car charger for your iPod and other USB chargeable devices. Plus its fun to DIY.

Typically, your USB port provides 5v of power through a single wire in a 4 pin USB cable. The normal operating voltage for most USB devices is between 4.75 V and 5.25 V. Ok great we understand that, but now how to get 5v from the 12 volt source (your car)? I stumbled upon this idea by accident, literally, I tripped over my wall charger for my Nextel-Motorola i870 and noticed that the adapter has an output of 5v to charge the phone. So, I went outside to my car to check the output voltage of my car charger, it was unmarked, so off to the Wal-Mart that is across the street I went to pick up a multi-tester. Upon testing the voltage output of my car charger I was astonished to see that sure enough the output was 5.15v well within the range to charge the iPod.

Read that last part again, I verified the voltage on a voltmeter. I also tested several other car adapters I had laying around, and the output voltages varied greatly, from 3v to 14v. So unless you are positive of the output voltage dont just splice away expect to get the right voltage to your iPod. (on a side note I also constructed a Firewire wire alternative from the aforementioned 14v car charger, and a tutorial for this one is coming soon). After verifying that the voltage was within normal USB operating range I used a USB extension cable to get a female USB plug. The next steps follow logically, splice USB female end to car adapter wires, seal, test voltage, go plug in. Direction and some pics follow.

Step 2: Parts and Equipment List

Parts and Equipment list:
- Motorola Car Charger for i205 i305 i315 i325 i530 i710 i720 i730 i733 i740 i830 i860 i870 cell phones.
Any car charger that has an output of 4.75v to 5.25v. (Note: I also used a Belkin Mobile Power Cord (#F8V7078-E-MK, $7.68 at Wal-Mart) which has an output of about 5.8v and it works fine as well, but to be safe, stay in the 5v range so you dont burn out the voltage regulator in your iPod. Also, be sure that your car charger has some sort of fuse protection)

-USB extension cable USB A/A M/F (you should have a least one of these somewhere)

Some sort of USB connection to your iPod I use an Apple iPod Dock Connector to FireWire and USB 2.0 Cable for everything that I do with my iPod, as its the only dock connector I own.
Voltage Meter

Soldering iron, Solder, heat-shrink tubing

A pair of cable strippers


Step 3: Step 1

Step 1: Verify that your chosen car adapter has an output voltage of 4.75v to 5.25v while plugged in. (USE Voltage Meter)

Step 4: Step 2

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Step 2: Unplug and cut the piece that plugs into your phone off. Strip the wires to expose the red and black wires.

Step 5: Step 3

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Step 3: Cut Female end of USB plug off of the USB extension cable, leaving about 8 inches or so to make room for error, and ease physical stress on your solder joints.

Step 6: Step 4

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Step 4: Strip the USB cable so that all shielding is removed exposing only the 4 USB wires. We are only concerned with red and black so cut the green and white wires as close to the bottom of the area that you stripped, as possible

Step 7: Step 5

Prep wires with heat shrink tubing (I forgot the first time, only to remember after soldering everything together, and I had no E-Tape)

Step 8: Step 6

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Solder red to red and black to black. Cover the joints so they dont short out, then heat shrink the whole thing to keep the joint protected.

Step 9: Step 7

Plug into cigarette lighter and verify voltage again. The pin-outs are located here ( just in case you are unsure. If everything checks out, plug your iPod in and charge away

Step 10: Follow Up

If you are comfortable with this type of set up, but would like to use a Firewire cable instead, use an adapter that has an output voltage of 12v to 30v. I have several adapters that output 14v constant, these are ideal to splice with a Firewire female wire. Coincidently, this cable ( would also allow you to mount the connector in the car (in dash, flush mount, console, or otherwise) and you can also hardwire if you wish.


Rosezdea (author)2014-03-13

This article is 7years ago.

Now, I think one new product can solve the problem.

There are already dual ports USB car chargers. Here I suggest one on the web:

You can see, there are already two ports output, it is enough for the normal use on the car.

And there are also 3 ports or even 4 ports output car chargers if you would like to search on google.

Anyway, thank you for the share! It is good article in 7 years!

thedra (author)2007-12-01

What are the blue(green?) and white wires? Just ignore them? Thanks

computerwiz_222 (author)thedra2008-03-17

These are your data lines. Sometimes they must be biased or terminated in order for the device to be recognized. This is especially true for the iPod.

jimmit (author)computerwiz_2222012-04-11

I highly recommend checking out this article from AdaFruit. It goes over the design of a USB charger and explains what different voltages on the data lines mean.

murph38_99 (author)2006-01-22

Since making this I also realised that 2 other things could be done in this manner. First, you could make an extra wall charger by using the motorola wall adapter (Model:PSM4680A) since it also has a 5v output. Secondly, you can use the unused male end of the usb extension cable spliced together with the part that plugs (the part you clipped off) into the phone, and still use the charger as a phone charger as well, simply plug the male end back into the female USB end and presto, you still have a functioning car adapter for your phone.

grungehead (author)murph38_992006-07-31

could said charger use 4 aa batteries... i know that equals 6 volts but then you could slap on a capacitor or resistor to make it 5v?...

fridelain (author)grungehead2012-01-31

(Yes, I know I am 6 years late to the party. It's for future reference)
USB chargers should output between 4.75 and 5.25 volts, and for full charging efficiency 1900 mA (Any set of batteries will provide more than that. Over-amperage won't damage your devices, as they will just pull what they need). Low power USB devices should be able to work with as little as 4.4 V, and all devices should be able to signal, if not work.
Now, a standard disposable battery is rated as outputting 1.5 V, and will at most of it's useful life, but when they are brand new they use to output as much as 1.6 and 1.7 volts, and they go down as they discharge. Most devices are aware of this and will work at 1.2 volts and up. Rechargeable batteries output at less voltage (Fully charged at 1.4 or less and for most of its use before recharging at 1.3 - 1.2), but have a less step voltage diminution graph.
Down to the math:
Brand new alkaline outputting 1.7:
3x1.7=5.1 (OK)
Brand new alkaline outputting 1.6:
3x1.6=4.8 (OK)
Less batteries you are too low, more you are dangerously high.
Used alkaline (1.5):
3x1.5=4.5 Low, but usable (-0.25v)
4x1.5=6, way too high (0.75v)
fully charged rechargeable (1.4):
3x1.4=4.2, too low (-0.55)
4x1.4=5.6, too high (0.35v)
Somewhat used rechargeable:
3x1.3=3.9 too low (-0.85v)
4x1.3=5.2 (OK)
Used rechargeable (1.2):
3x1.2=3.6 way too low (-1.15v)
4x1,2=4.8 (OK)

Most devices will have higher tolerances than the USB standard requires, but the question is ¿Do you feel like risking? In any case, under-voltage is much less likely to do damage than over-voltage.

lcolancecco (author)grungehead2011-05-11

It would be much easier to just use a zener diode and a resister in parallel with the diode on the + end, as a voltage regulator

cgcanada88 (author)grungehead2010-10-20

Yes, I think it is much possible. Probably won't get a lot of time, but will work great for an emergency charger for your usb phone.
Check this out:
for details on how to calculate the amount of resistance needed.

nodoubtman (author)2011-10-26

Your stuff doesnt work at all!!!!

baldmosher (author)2011-10-05

This post is relative specifically to HTC phones and I assume similar problems affect each specific device.

I've been researching this for a while as the HTC Desire is quite choosy about pulling >500mA (indicated on the phone as "AC Charging" rather than "USB Charging").

This whole thread goes into very good detail but this post in particular covers the issue nicely:

Adding resistors (max 200ohm) to the data pins will cause the Desire to assume it's connected to USB computer and therefore the phone will not try to draw more than 500mA. Indeed, it seems using a long cable (2m) may provide enough resistance to fool the Desire. So ideally, you want to short the data pins at the microUSB end. That's easier said than done, so you may have to experiment with a few different cables. YMMV and it seems everyone's does.

The basic points are that to get more than 500mA into your Desire, you need a car adapter capable of outputting enough current, and a good quality cable with the data pins shorted.

I would assume this applies to all HTC phones and perhaps many other devices.

baldmosher (author)2011-10-05

Simpler, yes. Powerful enough to charge high current devices, such as the iPad or HTC Desire, no.

chevelle350 (author)2008-11-10

This is great and is what I made this weekend (On my own, before I saw this.) The differences were that the first time I did not connect the data lines in the USB cable. This caused my Blackberry to not charge. I changed the data lines to ground. This lets the device charge for about 5 seconds, then it quits. Is there something else that needs to be done with the data lines? This same unit was used with a e200 series sansa. The unit did not charge with the data lines disconnected. I haven't tested the unit with the data lines to ground yet. I am able to use other USB powered devices with the cord. This Belkin unit is great for this job as it puts out good voltage -- it did a great job of charging my Motorola cell phone.

yes u have to connect ur data lines with a certain connection not simply grounded to start charging i've tried the above connection for my iPod classic and it didn't work i don't know the exact connection that u need for ur phone but i'm sure that u have to connect the 2 data lines correctly

For the HTC Desire, simply fusing the data wires tells the device it's plugged into AC power, so it draws more current than the 512mA USB maximum. I imagine it's specific to each device though.

dalmond1 (author)2011-08-04

Sus out this Video on Iphone charging very informitive

comicalmuse (author)2011-05-05

Not to put a damper on the build... but just wanted to share the option that you can buy a pre-built, clean, ready-to-go cig-USB adaptor on ebay for $2.38 with shipping... (or about $4 from US seller). Nice DIY, but just wanted to throw the option out there.

murph38_99 (author)comicalmuse2011-05-05

Thanks for your timely, relevant reply.

grimrencher (author)2011-03-07

great instructable, once i find the appropriate charger i'll give this a shot. i was planning on putting the circuitry in a small enclosure, hard wiring it to my accessory power, then putting a switch to turn it on and off when i need it. i'm pretty sure just putting a switch into the circuit would burn out the circuit (as this has happened plenty of times to me) so how would i work a switch into the circuit?

matroska (author)2009-07-14

I just finished a DIY solar usb charger, specificially for my iPod. I already knew that USB voltage varied from 4.5 volts to 5.5 volts.

My multimeter reads right now 5.20 or very close to this; I'm inside and it's night outside. With multiple lamps, that's what I'm reading. Yet my iPod is plugged into my female USB plug (salvaged from a dead motherboard) and nothing shows up.

I used this page for the usb pinouts:

What could I be doing wrong? :O Not enough milliamps outputted makes the iPod think it's still not plugged?

I also tried on a completely dead (battery) iPod, no results..

Thanks for any further help!

lasermaster3531 (author)matroska2011-01-31

also remember to short the two inner USB pins together to force it to charge, no resistors or extra wiring required.

so i took apart an old verizon phone adapter when i got a new phone and threw in a usb port i pulled from a dead board. connected the appropriate cables and my phone charges but not my ipod. so if im understanding your statement correctly inorder for the ipod to charge i need to short the inner two data pins? if this is so why is that?

lasermaster3531 (author)matroska2011-01-31

i'd say most likely not enough current. you would need a pretty big solar panel to get the whole half amp that a USB port should be able to put out. most likely the iPod can sense that and wont charge and/or the iPod's current drain is so high that the voltage drops too low. i would recommend building a solar AA battery charger and then using the charged batteries to power a MintyBoost mp3 charger or some such device.

Hibrid0 (author)matroska2009-11-21

I don't know if you already fix your problem... but I think you forgot to put an 2.5v connection on pin 2 and 3, this is because USB 2.0 standard give an 2.5 voltage for data pins and ipod need this to charge...(my iPod touch and iPhone needs that) so put a little resistence of 200 kohms from 5v to both middle pins.. (gnd unchanged).. and that work for me..

(I'm great reader but really bad english writer)

theazndan (author)2010-10-02

how do you make these lines biased or terminated?

shawnleclar94 (author)2010-04-10

can u play music in your vehicle with this

matroska (author)shawnleclar942010-05-15

 Hopefully you aren't thinking that this is a USB port for your car, because then you probably didn't read the instructable, or just deserve a big facepalm.

technoghost (author)2009-07-22

thanks for the idea dude heres how mine came out

ichainsaw (author)2009-06-11

Here is my rendition: I took an old nintendo DS car charger, stripped it and soldered it to a stripped usb male type B which plugs into a 6 port USB Hub. Now I can charge all my USB accessories from one convenient place!

UrbanWomble (author)2009-01-30

This is fun but I bought a very neat and tidy 5V USB adaptor for GBP1.50. As an intellectual exercise, this is fine, but an hour or so of my time has to be weighed up against such a small amount to pay! Have a nice day.

PhantomGamer (author)2008-12-18

I found this quest on a search of "12v to USB". My purpose for the search to see if any one else was building a BATTERY power to USB for (in my case my Sansa View) that would use one or two 9V batteries to extend the charge of the built-in battery for extended trips (Air Flights, etc...) where the Computer, Wall and Auto chargers would not be available. It seemd to me that using 9V rechargables would be an option if they would deliver their power to the USB like the Wall Charger does. Things I need to find out BEFORE I build the circuit: Does the Sansa View use 5V to charge or does it take more? Does it need the Data pins biased? Will the 9V batteries put out enough current for an extended period of time? I have already built circuits using a 5V regulator with a 9V battery to run pet project that use 4000 & 74LS series IC chips (which gave me the idea for this project). Reason for wanting to do this because the Sansa View battery is NOT replacable!! So what do you guys think??

okreneok (author)2008-12-08

I have 5 wires blue, red, white, brown, orange, and on my outlet i have white and red but i tried almost every combination of wires but my ipod does nothing why is this ?

bBuildnotbuy (author)2008-09-02

Real Question is how to protect from Over charging ?????? What rate mh and voltage is the safest for the device ?

mspitze (author)2007-10-25

For less than $3.00 you can buy one that looks clean.
This thing works great, uses a small buck regulator.
and you can mod it for you needs.

bartax (author)mspitze2007-12-28

Agreed, making this is not very practical but could prove to be a good exercise.

Quiksilver2693 (author)bartax2008-04-24

They have things like these at target and other places of the sort.

skaterdad (author)2008-04-24

So, I didn't have 47K resistors on hand, but had 39k resistors... built it up and 3g Ipod Nano showed "charging" for a little while but then stopped (even though battery not showing full). Also, when it showed "Charging" the menus on the ipod are VERY sluggish.... seems something is wrong here... any ideas?

mamaynhan (author)2008-04-01

so when you finished how can we charge our ipod?????

ranjeevm (author)2006-04-27

Nope! this is the right one!

antennas (author)ranjeevm2007-10-10

Drop a pair of your 47K resistors. No need to have two dividers doing exactly the same thing. Simply wire both pins to the same point between the one divider. Save the parts for another project.

computerwiz_222 (author)antennas2008-03-17

now you are defeating the purpose of the voltage dividers. Once again, you have simply created a short.

antennas (author)computerwiz_2222008-03-17

No you simply are giving +5 to both pins. "Short" technically, but it doesn't matter. Both are at a 5V potential. You are wasting parts to use 4 resistors when you only need 2. Try it you will see.

ranjeevm (author)ranjeevm2007-10-11

Just to answer all the recent conversations: Shorting 2 data port for the sake of 2 resistors is NOT a good idea. There is no guaranty that these data points do not try to swing away from a tristate and throw a 1 or a 0 at these ports. If one throws a 1 and other a 0, that would be a dead short-circuit!! I am designing for an 'alien' design and do not want to get into any assumptions and possibly ruin my iPod for a few cents (cent wise and dollar foolish?). Some designers do base theirs on assumptions you see and that's the reason why there aren't many good products out there! Same applies to the 1 ohm resistor. We all know that the internal resistance of a lead acid battery is very low so if a hooked devide draws a surge, that could be enough to blow it off or if you are lucky at least the fuse. The 1 ohm resistor shall 'waste' close to 200mW (cost? Not even measurable in penneys) and give you big time potection. These are my justifications - yours may differ. Just remember that the clutter that some of the comments cause makes the most useful ones invisible to the reader! Thanks!

computerwiz_222 (author)ranjeevm2008-03-17

What if i subbed in a 60 ohm resistor for the 1 ohm. I have no 1 ohms on hand. (of all the values i have lol, i have at least 100 different resistors...) This would simply result in a higher "waste" as you say. If I am using lithium polymer batteries, would I need the 1 ohm resistor?

ranjeevm (author)computerwiz_2222008-03-17

Be very careful about Li Ion or Li-po batteries as they have the potential to explode and cause fair bit of damage/injury. I have not read up any literature/data sheets pertinent to this and so unable to comment at the moment. If you use a 60 ohm resistor, chances are that the battery will need more than a week to charge instead of a few hours! I would not recommend tinkering with Li-po batteries unless you are sure of the results.

computerwiz_222 (author)ranjeevm2008-03-17

Acutally, the battery pack is an old portable dvd player pack with an internal charging circuit. I am not worried about them exploding or anything because when they are finished charging, the the green light comes on and then the voltage drops across the battery terminals. What i'm doing is building the one all solution circuit shown earlier inside the case of the battery in the extra space in the case. I am getting about 7 volts before regulator and about 4.91 after. I still have yet to get anything to charge though...

GorillazMiko (author)2007-08-22

Hi, when i opened my car charger thing there was WHITE and RED. When I opened my USB there was white, red, green, and black. I soldered the WHITE and REDS together, will this still work?

Grab the pinout for USB, don't go by the colors. I have seen USB cables with orange and green used for the voltage. The extremely cheap USB cables from the dollar store are usually not colored right.

chr15sc (author)2008-02-01

I have used 2 pairs of 20K resistors as voltage dividers. The output of each goes to the D- and D+ separately. This worked straight away.

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