I did an experiment with a portable battery that I have purchased for 39 dollars on Amazon.com. I found that R10 and DX100 can run with an external battery power via USB. (There's no portable battery with V5 cord out there)
Connect any of your portable battery with USB to R10 / DX100's android USB port. It won't show the charging mark. Instead, It will run on that external battery! R10 / DX100 will not use its internal battery till it completely drains the external battery.