I love adding discrete upgrades to my vehicles, and USB chargers are always on the top of my list of accessories.

While the photos are specific to my GTI, this can be done on any car/motorcycle/boat/etc. The only change is finding the right fuse to tap into.

Overview:

Find fuse to tap
Connect lead of fuse tap to 12V -> 5V converter, and ground to ground
Plug-in fuse tap and phone charging cord
Charge!

Parts list:

Mini Fuse tap ($6): http://www.amazon.com/gp/product/B00UB9W92C
- (or full sized ($8)): http://www.amazon.com/gp/product/B0002BGELQ
3 amp, 12V to 5V Double USB converter ($9): http://www.amazon.com/gp/product/B00XDSA82Q
- I plan on adding other USB devices in the future so I opted for 2 USB outs.
Phone charging cord (this one is for the iPhone)($8): http://www.amazon.com/gp/product/B010U3XVMU
Optional - Windshield/Dash Phone mount ($20): http://www.amazon.com/gp/product/B00JRGOKQ8

Total = $31 ($51 with mount)

Tools (for MK7 GTI):

Flat head screwdriver
- optional - small towel or cloth to cover screwdriver and avoid possible scratches on the dashboard
Needle nose pliers
Small crescent wrench
Soldering iron or crimp connector
Electrical tape or heat-shrink tubing
Optional - multimeter

Step 1: Find Fuse to Tap

For more information on the MKVII Golf fuse box check out this post:

http://forums.vwvortex.com/showthread.php?7072478-...

For the MK7 Golf, we will use the 7.5 amp fuse mentioned in the link. This fuse switches on and off with the ignition and is rated up to 15 amps.

It's always advisable to test the fuse with a multimeter to be sure it does what you want. Set the multimeter to 20V DC, and put one end on the metal bit of the fuse, and the other on a ground (unpainted frame or bolt).

When you turn the car on it should read between 11.7-13.5V, and turning the car off it should be 0-0.03V.

Step 2: Assemble the Fuse Tap and Converter

The mini fuse comes with a 2 or 3 amp fuse which is plenty for a phone, and also the max output of our converter.

Fuse taps only have a hot (+) wire since all electronics are grounded to the frame of the car. This way the ground (-) can be easily connected to a bolt or piece of unpainted frame.

Simply solder or crimp the red (+) wires together. Be sure to cover the connection with heat-shrink tubing or electrical tape.

Step 3: Plug It All in and Enjoy!

The interior fuse box is almost always located under the dash to the left of the steering wheel. Mine is behind a pull-cubby that pops out cleanly with a bit of wiggling and tugging. I also removed the side panel to run the wire along the A-pillar. The side panel has three tabs that snap it in place.

Once you've located the fuse you want to tap, pull it out with the pliers and insert it in the slot next to the provided fuse.

Next, plug your fuse tap into the same spot, and tuck the wires away. Once you have it all plugged in, turn on the car and test it with your phone. Then, turn off the car and make sure that your phone stops charging.

Snap all the panels back in and admire your work!