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Galaxy Nexus Wireless Charging

melchior00 -

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Mi Problema

I didn't have a problem with my Galaxy Nexus, but I did want to be able to charge it without fiddling with a USB cable. I found an intriguing mod involving a Palm Pre Touchstone charger and some copper foil tape, and I thought I would give that a try.

Mi Solucion

It was my very first shot at opening up a mobile device for any reason, so it was daunting and exciting at the same time. Although the teardown guide for the Samsung Galaxy Nexus was very helpful, the CNet teardown video was also a big help.

First, power down the handset and remove the battery cover and battery. Remove the tiny #00 Philips screws, and pry the chassis off the screen. There are 4 tabs that hold the chassis in place-- use either the plastic tool, a thin blade (if you're feeling really brave), or some guitar picks, and kind of jimmy around until you hear something pull loose with a "click". Repeat on all 4 sides of the screen.

I used (and mangled) the plastic opening tools to avoid scratching up the screen, and guitar picks to help pry the catches in the chassis loose.

There are 3 pogo pin contacts in the chassis, that end in gold contact pads. Stock Samsung docks use these pins to charge the device and receive audio, much like the iPod connector. I extended the outer 2 pads to the battery housing area using copper tape, being careful to mask off nearby circuitry with some orange high temp electrical tape (thank you SparkFun).

Using a Palm Pre Touchstone and some thin neodymium magnets, I plotted out where I would place the inductive charging coil on the extended battery door. Using a sharp knife, I whittled down any plastic molding and support that would bend the coil or otherwise get in the way.

Next, I removed the inductive charging coil assembly from the battery door of a Touchstone kit for the Palm Pre. I soldered 2 pieces of copper tape to the gold contact pads on the converter circuit, then affixed this assembly to the door for the extended battery, aligning the copper tape to the contact extensions I made earlier.

Finally, I installed the battery, snapped on the door, and tried it out. Success!

Mi Consejo

- Patience is the key to removing the chassis from the screen. You may want to start by inserting the plastic opener near a physical button, between the screen and the edge of the chassis. TAKE YOUR TIME-- DO NOT USE EXCESSIVE FORCE, or you may find yourself with a cracked screen.

- The contacts on the Pre charging circuit must be soldered to the copper foil, rather than simply taping the copper surface on. Otherwise, there's just not enough juice to get the phone to start charging. It'll be hard not to get a cold solder, since the joint is pretty hard to connect as it is. You may want to do this before attaching the circuit to the battery door.

- The battery door fit is going to be tight with the extended battery. If you have a lot of patience or a Dremel and steady hands, you could probably make the coil assembly fit in the door less tightly, and thus have all the tabs of the battery door snap in place.

- You'll need to pad the contacts in the battery well area, so they will contact the copper on the door. The guide suggested 3M automotive trim tape, and having tried that, it worked very well. Expensive stuff, though.

- Copper tape and electrical tape (the same kind used inside notebooks) can be found online. The guide didn't mention masking off circuits or components near the dock pin contacts, but I figured, better safe than sorry. It's also a very good idea to trim down the copper tape as needed; I have a pair of Tamiya hobby scissors, but any small pair of scissors ought to do the trick.

- The iron discs that the Touchstone uses to magnetically align the coil are rather small, so I used the aforementioned thin magnets on the Touchstone to make sure the "grip" is stronger. The Micro USB connection needs to provide at least 700 mA of current, since you're going to lose some energy inducing a current in the coil.

- Since the WebOS smartphones are all but discontinued, the Touchstone kits are quite inexpensive now. If you're thinking of modding your phone for wireless charging, now is a great time to get a Touchstone and start tinkering.

- I haven't tried the NFC (Android Beam, Google Wallet)... yet. I'm told there shouldn't be a problem with these, as I've positioned the coil pretty high up.

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