You're local hobby shop probaly has some sort of cheap Voltage Checker you can pick up, so you can have a quick check after a serten run time, just to get an idea were you are at . I have several brands for my 8.2e . turnigy , rb ad dinogy, With mah ranging from 5400 to 7000, so before I get the 'feel' for the run time , and also since I have been fooled by the ESC in my boat , I like to pull over once in a while and quickly plug in the V Reader to get a read