Running Linkitone with 5V 3A UBEC

I would like to run my Linkitone from a 12v Battery in order to reduce the voltage I have a 5v 3A UBEC DC/DC (Buck) converter.
The battery input on the spec sheet says 4.2V.
The question is:
What is the upper voltage limit on the battery port.

The upper voltage limit is 4.2V.