It shouldn't be too hard.. The pbook runs on 11.1V, so any 12V battery should work. The easiest way to approach it IMO would be to hack off the end of the sony AC/DC adaptor that goes into the pbook, figure out the wiring scheme and solder those wires to the approriate pins on a 4 pin XLR, assuming you will be using a battery with a 4 pin recepticle. The Sony quad. cap battery is rated at 6.2Ah, so you need to make sure you find a battery with a similar capacity to ensure you have enough run time.