1. Take apart your USB car adapter, carefully separating each piece with needle nose pliers. Take out the center piece with the USB port. The curved sides are negatively charged, and the center square is positive.
2. Take your 9 volt battery clip and line the red wire up with the positive part of the USB piece, and the black wire up with the negative part.
3. Tape the two pieces in place, and heat up your soldering iron.
4. Hold the solder against the wire, and gently tap it with the soldering iron until a small amount melts over the wire. Let it sit for about a minute until it hardens.
5. Once the wires are attached, plug in the battery to the clip. If your USB adapter has a light on the front, you should see it light up.
6. With an empty mint container, punch a hole in the side with a nail, and widen it with needle nose pliers. Push the USB port against the hole, and tape in place with electrical tape. If your mint case is big enough, you can store some extra batteries.
7. Plug in your phone charger cord to the USB adapter, and plug in your phone. Enjoy juice on the go!