HOWTO: charge VX8100 through USB with Verizon cable

**Spiral** · #1 (**permalink**) 06-22-2007, 07:57 AM

Tuto by obusago

The USB cable I got was part of the Music Essentials Kit which I thought was interesting enough to sink $29.99 into because it also has the stereo headphones and drivers that are guaranteed to work with BitPim (I don't use the included MediaPlayer 10 -- version 9 works just fine).

I like that the cable will let you plug in the adapter so you can charge it while you have it connected to your computer, but I've heard of cables that let you charge from the USB port so I was a little disappointed that that wasn't possible. After all, I may take the cable with me when I'm on the road (I'll buy a bluetooth adapter when I get my rebate back) but I'm not always going to have power available.

I searched this website and others to see if anyone had modified their Verizon VX8100 USB cable to charge the phone while it's connected, and it appears that no-one has mentioned doing that, even though it's easy to do if you have a soldering iron. So I decided to pay back the community on this message board for the excellent information, by writing this how-to.

IMPORTANT: This will void the warranty of your cable, and maybe your phone and/or computer. I tested this and it works, but I won't take responsability for anything you do with your hardware. Do this at your own risk! Also, the usual "Your Milage May Vary" warnings apply: it's possible that there are (or were) different versions of the cable in production with slight variations in how they're made, e.g. wire coloring or circuit board layout. The circuit board in my cable had date code "4605" (probably week 46, 2005) on it, in case you want to compare.

YOU WILL NEED:

A soldering iron with a fine tip
A steady hand
A diode, e.g. 1N4148. you can probably get these at RadioShack, if they don't have this particular type, just get another one, it doesn't really matter. If you don't have one of these, you can use a piece of thin wire, but if you use a piece of wire instead of a diode, make sure you NEVER attach your adapter to the modified cable while it's connected to a USB port!, or you might break your USB port or your AC adapter. The diode allows you to connect both USB and the AC adapter at the same time if you don't want to drain your laptop's battery (but of course if your AC adapter can use AC, your computer can too and it doesn't matter).
Optionally, a small switch to switch USB charging on/off. Recommended if you are using the wire-instead-of-diode option!

HOW TO MODIFY THE VERIZON MUSIC ESSENTIALS KIT FOR THE LG VX8100 TO LET IT CHARGE THE PHONE THROUGH USB.

Disconnect the cable from phone, USB port and AC adapter! After this, there is no reason to worry about zapping your computer, phone, adapter or anything else because of currents running to your grounded soldering iron, or because of static electricity (there are no electronic components in the cable that are sensitive to static electricity).
Open up the junction box in the middle of the cable, there are 4 screws (two on each side). Once you have done this, don't jerk the cables around too much to prevent breaking the wires right where they're soldered to the circuit board.
With the connector towards you and the wires going left and right, you should see a circuit board that's connected to the USB connector via 4 wires on the left, and to the phone via 7 wires on the right (plus two wires at the other side of the circuit board but we only need to access the top).
The 5V power from the USB is connected to the topmost contact on the left with a red wire, the 5V power from the AC adapter is connected to the phone's charging inputs via contacts 6 and 7 on the right with brown and red wires. You have to connect the diode (or piece of wire, see above for warnings) between USB power output and charge power input. The side of the diode that has the black or wite ring (or the line if the diode only has a symbol that looks like a triangle with a line attached to it) should be connected to the charge power input of the phone, the side without the ring (or the side that's closest to the triangle) should be connected to the USB power. Don't worry if you get the direction of the diode wrong the first time, you can always desolder it and turn it the other way if it doesn't work. Make sure the wire(s) that you add don't touch any other contacts than the ones they are supposed to touch!
Optionally, if you don't always want to charge via USB, you can put a switch between the diode and one of its connection points (or between the connection points if you don't have a diode). If you can find a switch small enough to fit in the junction box, that is -- I didn't have one so I just used the diode.
That's it! As soon as you connect the cable to your computer, the phone will start charging. When it's done charging, the phone will show a message saying it's fully charged; that message may be shown more than once because you're draining the battery because you're using it to do cool stuff, right?

WHAT YOU NEED TO KNOW

On most laptops, the USB ports are powered while the computer is off.
The phone doesn't tell your computer that it's draining extra current from the USB port, which it should do according to the USB standard. If you hook other USB devices to your PC that require current, the amount of current required may exceed the rated power of your USB controller or hub, which may break it! Normally the amount of current a USB controller should be able to supply to a USB device is 500mA; I don't know how much current the phone draws during charging but my AC adapter is rated for a maximum of 1A (1000mA). I don't think it needs that much current but it's probably a good idea to leave one USB port on the same controller(!) free when you use the modified cable.

I attached a photo of the inside of the junction box with a diode in it; sorry it's not very sharp but the only thing I had handy to take the picture was the camera in the phone and it doesn't do well at short distances :hehehe:. As you probably can't see, it's soldered to the #1 and #7 contacts on the right side (phone side), connecting the USB power to the charge power input.