The adafruit website lists that any wallwart adapter from 5v to 12v will do and also the USB socket can be used to charge ,so both of these 2 different options makes us looking at a minimum voltage threshold of 4.5 to 5.5vdc (depends on pc to pc hardware on usb output voltage) meaning that the board works with at least a minimum of 5vdc input to charge the single cell lipos.