1. Cut 2 iPod|iPhone|iPad Cables
2. Identify and verify the cables that carry power (in case you are not using the apple supplied cables) - usually they are red (+5V) and black (G)
3. On one of the USB cables, cut and isolate the data cables (the two cables NOT power related as in item 2 above)
4. Reconnect everything (I used a small veroboard, but just simple splicing/soldering should be okay) - Just make sure you connect the power cables IN PARALLEL.
5. Insulate and test (I used Sugru to create a more hardy enclosure)
This has been tested to bring up a 7% battery charge iPad to full in about 5 hours - more testing is underway for validation)