Hey guys i think i figured out a simple equation to accurately calculate the length of flight times based on the mah (milli-amp-hour), and the amperage draw from all your motors combined. Here's a couple units so you can understand better. 1 amp-hour will supply a continuous current of 1 amp for 1 hour 1 amp = 1000 mah Equation: (XAmps·1000)∕60 This equation calculates how many mah's consumed per minute based on your overall amperage draw from your motors. So you can then take the amount of mah's in your battery pack and divide that by your result from the equation. Which results in the amount of minutes you will have. I base my amperage draw off of 65% power continuously. You can find the amperage draw from the website of the motor company you bought from, (most of them). Example: One of my motors draws 9 amps continuously at 65% power. I have four motors so 9 times 4 is 36. So 36 total amps being drawn from the battery. Equation: (36 x 1000)/60 = 600 mah's consumed per minute. I have a 9000 mah battery. So 9000/600 = 15 minutes of 65% continuous power usage.

Did you measure amp draw with your prop installed? Did you factor in amperage draw under full weight load? Did you factor in the differences in amp draw between two of the 4 motors as you pitch forward or yaw or even roll? As good as it sound there is too many variables to "accurately " measure flight time....Its the same with 1/4 mile ET and MPH formulas based on horsepower and weight....Just too many variables in between for it to be accurate but it is fun to play with and somewhat close.

Most prop charts from the motors you bought will tell you what amperage draw there is with specific props. And all the tests done are under "average" weight load. And if you want very specific calculations, you can record your yaw and pitch movements for the average flight, where you could than determine what extra amperage is being drawn.

A few things to add, you need to consider what capacity you are discharging to, and the inefficiency like 15% or so. Just to get a bit more accurate calculation