How much would the Wii U cost if the hardware has its own battery?

[Soleron]

The Wii U consumes 32W during a game.

The Wii U gamepad has a 5.6 watt-hour battery.

If you wanted to run your Wii U for 6 hours without a recharge, you'd need 34 Gamepad batteries in the thing.

In other words: not possible.