How to choose the right electric speed controller, battery amperage and motor proppeler?

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1

Hi everyone ,i am new to this drones world , i just wanted to build a drone myself but i don’t know where to start.
i want to build the drone myself with separately parts and a 3D printed frame, but first i have to know the propeller dimension to build the frame for that i have to know the weigh of the frame to choose a good motor to can handle the all thrust that i need…
First i found that the MT2206 2200 KV brushless motor would thank my requirements.
so i started to calculate how i’ve seen on forums;

 - at 11.1v  it need 16.2Amps so the total drone will need  4x16.2 = 64.8 A + amps for other electronics about 65/66A (so we need 66 amps for the installation - current drawn)
  - let chose a battery: i found the VENOM 20C, 3S, 5000mAh LIPO would be a good choise

5000mAH-5Ah -> 20x5 = 100A; so about 25 Amps for each motor minus the amps required for other electronics
- chose an ESC (i dont understand) - so the motor require only 16.2A each, if i deliver about 25A it will take only how much it really needs to run so it won’t burn or something , i understood that the ESC current must be at leas with 20% more than the motor required current (16.2A x 1.2 = 19.44‬ A - 20AESC) but i also have seen that the ESC current must be higher than the battery current delivered (25A x 1.2 = 30A ESC) soo it won’t burn (the amperage of the esc refer that it can support only 30A so the battery couldn’t deliver more of that or it need 30A to run the motor so the battery need to have more curent than the ESC to handle the requirement ??)
- finally the i saw the recommended Propellers - 6045 - and i god a total of 1067 grams for the hole drone that means 2x1067 = 2134‬g / 4 = 533.5‬ grams of thrust on each motor , this motor can handle this…
- BUT THE PROBLEM HERE IS THAT I’VE GOT ONLY ABOUT 15-18 MINUTES OF FLYING , THAT IS TO LESS THAN I WANTED !

After that i found a package with 4 motor, 4 ESC and 4 propellers(

motor - T-Motor AIR 2213/920KV
ESC - T-Motor 20A
prop - T9545
)
This kit is able to handle a 1200 g - 1500 g drone weight with a maximum 1084 g of thrust per motor with 18 A max current drawn -> 18 x 4 = 72 A + amps for rest of the instalation = 72 + 3 = 75 A
They have a recommended or included ESC of 20 A (if i calculate with 20% more of the motor current -> 18 A max current drawn x 1.2 = 21.6‬ A ESC NEEDED, if i calculate with the amperage value from that picture - 14.3 A at 14.8 Volts -> 14.3 x 1.2 = 17.16 A ESC needed) but if i will put a battery with a bigger amperage delivered i will burn the 20A ESC so i need a battery with max amperage under 20A of the ESC but bigger than the minimum curent needed (75 A for installation /4 = 18.75) so about 77.5 A battery.
If this calculation isn’t right and i can exceed the current of the esc with the current of the battery then is fine…
The commanded prop is a T9545 propeller with a diameter of 9.5 inches = 24.13 centimeters that is a huge diameter , for that i will need a minimum drone diagonal of 24.13 x 2 = 48.26‬, + 3,4,5 cm = about 50 cm long , that seems to need a huge frame so i will exceed the thrust needed for this motor so i have to chose a bigger one. Because of that i was thinking to pun a smaller prop about 6 inches = 15.24 cm because i found that the flight time will increase if ;

  • i use a lower Kv motor with a bigger propeller = this motor will easy handle the 6 inches prop
  • i use a lower Kv motor with a bigger battery and enough C rating
    What is the C rating ? if i multiply the C rating with the mAh of the battery i will get the max Amperage drawn from the battery, which one of these things need to be bigger to get a longer flight time , the c or the mAh because the Amperage id the same if i will increase one and decrease other?
2

Yes, your motor will take as much as it needs from an ESC, so there is no harm using a higher rated ESC for the motor.

Make your quadcopter alot lighter to improve flight times, or try more efficient motors with larger props

3

Hi, thanks for answering me! Ok i understand that the motor will take only how much Amps it needs from the ESC but the esc Amps how these need to be ? bigger than the battery Amps or lower (what represents the number on the esc , it says that this esc will support only 30A input or it would take 20 A so we need to be able to deliver more Amps if is needed?) i saw an example of this in this video https://www.youtube.com/watch?v=LlSa2f76QiU&t=1s , it used a 60A esc on a lower amperage battery . that means the ESC amps are bigger than the batt.
Higher propellers with a low Kv motor will decrease amperage draw but i will need a bigger frame for the propellers so also a bigger thrust motor. The battery mAh x C rate is the maximum current draw from the battery (ex if a must be able to draw 60A - the instalation require , if i use a 5000mAh with 20C battery 5x20 = 100A , will work ? or the battery must have al least 60000mAh??)

4

You are over complicating the fun of building. if you are using mt2206 2200 motors a 6 inch prop of around 4" pitch and a 25 or 30 amp esc will be fine.probably go for a 4000mah as its a little lighter. the most flight time ive ever had is 19 mins and that was over discharging the battery, and flying relatively slowly.
15 18 mins would seem good.
bigger battery more power used to keep heavy quad in air. smaller battery less weight but less mah to use.

5

Thanks for answering, in your country what rules do you have, drones over 500g of weight need to be certificated and need approvement for every fly, no cameras are allowed , no flying in city , flying at maximum 300 meter altitude…? is pretty hard to build an under 500 grams drone with powerful brushless motors and other heavy components , with that rules you could build only a drone with small 6 mm diameter dc motors… .The rules saw that no filming devices are allowed on the drone but the FPV camera is not filming it is transmitting a live view?

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