I did not found any information about the battery charge of GPS Route logger Dongle model GT-730-S.
For this device, the battery charging indicator is given through LED colors. When the device is attached to PC, the charging mode is indicated by the red color. This is extracted from the datasheet for this device:
If you want to download the PDF file for yourself: http://akizukidenshi.com/download/ds/canmore/GT-730FL-S(SiRF)_DataSheet.pdf