Today I found another piece to my project... which is add an external power source to use it outside. It is better than add a power source, is to create a circuit with a power regulator of 7-40v DC, which opens many ways to power up the raspberry pi.

There it is the link.

Thanks to Morteza Mirmojarabian work, I have a way to you leave your comments... see how here.

Meanwhile I found this two power converters in DealExtreme:

http://dx.com/p/166930 e http://dx.com/p/151211

One more thing to later think a little better about.