Proper Motor/Prop/ESC Specification

[PilotHal]

I'm trying to wrap my head around the various concepts related to selecting the proper motor Kv and prop size as well as selecting the proper ESC for a specific motor of choice.
When looking at the specs on a T-Motor, say for example the MN4012, the manufacturer specifies the various characteristics of the motor along with prop suggestions. One column of interest is the (A) column; showing the total amount of current the motor will draw at different percentages of throttle.
In the case of the MN4012, when using a 13x4.4 CF prop at 100% throttle the motor will draw 9.4A - see attached image.

My question is why do people spec out a 40A ESC if the motor (in this example) will only draw 9.4A? Furthermore, the motor will only draw a maximum of 25A continuous.

So, wouldn't a 35A ESC be sufficient in this case? Most people are not running their motors on their multi rotors at 100% continuous - maybe for brief throttle "punches" - assuming hovering is at mid-stick or 50% throttle, you could use 65% power as the average current draw. For the example motor, that would put you at 4.8A of current. Even less that 9.4A.

Does anyone have the logic for how you spec out the proper size ESC for a multi rotor motor/prop configuration?View attachment 15169

 

[Silverburn]

I'm trying to wrap my head around the various concepts related to selecting the proper motor Kv and prop size as well as selecting the proper ESC for a specific motor of choice.
When looking at the specs on a T-Motor, say for example the MN4012, the manufacturer specifies the various characteristics of the motor along with prop suggestions. One column of interest is the (A) column; showing the total amount of current the motor will draw at different percentages of throttle.
In the case of the MN4012, when using a 13x4.4 CF prop at 100% throttle the motor will draw 9.4A - see attached image.

My question is why do people spec out a 40A ESC if the motor (in this example) will only draw 9.4A? Furthermore, the motor will only draw a maximum of 25A continuous.

So, wouldn't a 35A ESC be sufficient in this case? Most people are not running their motors on their multi rotors at 100% continuous - maybe for brief throttle "punches" - assuming hovering is at mid-stick or 50% throttle, you could use 65% power as the average current draw. For the example motor, that would put you at 4.8A of current. Even less that 9.4A.

Does anyone have the logic for how you spec out the proper size ESC for a multi rotor motor/prop configuration?View attachment 18954

Use ecalc.ch for working it out.
- ESC choice is dictated by input volts and the maximum amp draw of the motors
- Real world Amp draw figures can be considerably different to those stated
- Be wary of just using amps; The MN series have quite low maximum watt ceilings (circa 300W). I know from personal experience that if you go beyond it - even briefly - they overheat quickly and start exceeding the stated maximum amp draw. Another reason to have a good overhead in your ESC. I tend to use a *minimum* of 10A of overhead.

 

[mechanike]

yeah better safe than sorry,,,,,,,,,,,,,,i have 50a motors with 30a esc's simply cause the 40a esc's won't fit anywhere.i put then inside the globe,with large heatsinks i added,and a fan which blows the heat off of them onto the kk2.0 which keeps the flight contoller happy at 10 below 0f,,,,,,,,,but thats just me,,,,,,,,,,,,,,,,,,