Recent buy.com 770 owner. I found this tip by Kensington that allows you to charge via usb. I did not see this accessory posted, so I hope this is not old news.

http://www.circuitcity.com/ssm/Kensi...oductDetail.do

With usb power adapters available for the car and house, you can charge as needed even when not at your computer. I also have several rechargable external batteries with usb ports. I hope this helps someone.