# Motors and battery for a quadcopter

Hi all!
Basically, these are "The Questions" of every newbie like me.

1 - I'm trying to figure out the relation between the maximun weigth (comprising payload) of a quadcopter and the motors required.

Somewhere (can't remember where) i found that, to not stress too much the motors, this relation should be followed:
Maximum Weigth of Qaud (comprising payload) = Maximum Motor Thrust x 4 / 3
Is that correct?

2 - About the motors: Searching the websites i can find products like this one where i can easily find the thrust of the motor, or i can find products like this one where there is no indication about the thrust (like the most of the motors i've seen so far). How it's possible to know the thrust of the motor in the second case?

3 - Once i have the motors and the ESCs i have to find the rigth battery pack for the Quad. So if my motor use a Max Current of X, than my battery pack should drawn at least 4*X current?
Consider the 2200 mAh battery 30C,  so 2200*30/1000 = 66A > 4*X?

For instance, let say i want to build a big quad for aerial photography, with motor to motor distance of 90cm. The frame weigth is 650g (using Alluminium), plus
the ArduPilot Mega and Oilspan 50g, plus payload of 500g for the camera.
So i have 1.2 kg weigth so far.
What kind of characteristic should have the motors? And the battery?

4 - When i connect the ESCs to the battery, the ArduPilot Mega will take the necessary energy to work from the ESCs (this page)?

Hope someone will help me (and all the other newbies). Sorry for all these questions!

Views: 16991

### Replies to This Discussion

Davide,

thank you Chris!
Same questions :)
Have a look on RCGroups http://www.rcgroups.com/forums/showthread.php?t=716870 a very long thread but it has covered motor types, thrust etc.

The frame I have just built weighs in at 1.4Kg ready to fly (battery, motors, ESC's, etc). I am using KDA20-22L motors and Turnigy Plush ESC's, and APC 10 x 4.7 props and 2300mAH 3S pack. This is a fairly standard arrangement (see link above). One aspect of motor selection that it is easy to overlook is vibration.

The standard seems to be to use the BEC in one ESC to power the APMega (the others being disconnected so they don't fight each other) but I am using a separate BEC. Please be aware of problems connecting the USB and BEC power to the APMega at the same time.

regards Peter

Peter

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