Thanks DiegoV.
Good explanation, i understand all question.
If someone have my same objective i'm going to explain my workaround:
Connect the battery to J2 header, cut the 5V trace on expansion board and connect the battery + to 5V output in power header. I'm using an external stepup (TPS60110) to gain 5V from battery.
5V is big trace that run under POWER and ANALOG IN label of power and analog header.
Regards.
Marco