I am just doing this for simple reason "load shedding" and getting uninterrupted internet without getting disconnected.
so i found this device called Car Power Converter Inverter Adapter Charger with USB which should do the job as advertised
i believe it can charge from USB and provide the sufficient power supply to my modem which normally is rated b/w 9v to 12v.
here are some specs.
Input voltage range: DC 12V-24V
USB Output: DC 6V
How good this device will work or not work? any ideas