About the UBoost from Nyko, keep in mind that unlike the actual Wii U Gamepad battery, it doesn't inherently extend the battery. This means that the Gamepad will hold the same amount of charge even though you attach it. The way it works is that it functions as a battery storage. If you want to give power to the Gamepad, you attach this thing and press a button on the extension and it will charge the Gamepad.

I know about this since I have one.

Thanks for reading.