To monitor the voltage of the internal rechargeable battery of your COBRA2, click on the percentage reading of battery voltage in the "Bat" column in your Admin login:
This will pop up a graph showing your COBRA2s "Battery %" from the internal lithium, as well as the raw voltage reading from the external power source. If the external voltage is not displaying you can add it to the chart by clicking on the '+' sign on the top-right of the 'Data Series' box. Select 'PIC Battery Bulk - External Voltage' from the Input drop-down menu then click 'Add'
If your external source is a solar panel, note the daily voltage profile generated by the sunlight hitting the solar panel: