According to the transmitter specifications, it draws 170 milliamperes from the battery. That is the current going from the battery into the transmitter. The battery capacity is 600 milliampere-hour. That means it will supply 600 milliamperes for one hour. If less current is drawn from the battery, it will last longer. If you are drawing 170 milliamperes from the battery, it will last (600/170) 3 1/2 hours. You can leave yourself some margin and fly for two hours without recharging. Dan.