KnowHow 133 episode On the AlienX quad you mentioned on the notes that if you 're using 8 " p...

[G+_Paul H]

KnowHow  133 episode.  On the AlienX quad you mentioned on the notes that if you're using 8" props you can go with a 4S battery but if you're going to use 10" you should go with a 3S.  I'm a little confused since wouldn't a larger prop require more energy and thus require a larger battery?

[G+_Travis Hershberger]

A larger prop is also going to draw more current through the ESC.  So with an 8" prop the lower current means you can run a higher voltage and still remain under the amperage rating of the ESC.  Go to a 10" prop with a 4S batter and you will most likely draw more power than the ESC can supply and release the magic black smoke.

[G+_Paul H]

So the bottle neck happens with the esc and not the motor?  Will changing to a higher capacity esc fix that problem? Is there a way to determine the current draw by a given battery, motor, prop combination?

[G+_Travis Hershberger]

They have those formulas you can use to plug in the numbers for your own setup in the show notes for a couple shows.  Fr. Robert Ballecer, SJ or CrankyHippo remember which shows those were?

[G+_Travis Hershberger]

It's not just the ESC, it's also what the motors can handle, the ESC, and what the battery is able to provide.  It all needs to mesh withing certain parameters.  Fr. Robert Ballecer, SJ mentioned in the last show that the motors can burn out if you push them to hard for to long.

[G+_Paul H]

Thanks. What motor brand are you guys using. Looking for a mid level brand that's good quality but won't break the bank like a kde or t-motor

[G+_Fr. Robert Ballecer, SJ]

Paul H In my builds I'm never limited by the ESCs. However, the motors only have a certain amount of current you can pass through them before you burn out the windings.

 

A 10" prop will pull a lot of current because of the load, but it spins more slowly because it's a 11.1v battery vs. a 14.8v. (3s vs. 4s) and therefore stays under the "current limit."

 

A 14.8v battery will spin a motor more quickly, and therefore have increased current draw, but the smaller prop has a lesser load, and therefore keeps us under the "current limit".

 

So... large prop with lower rotational speeds, or smaller prop with higher rotational speeds. The first will give you a more stable platform that is also more stable for videography, while the later will give you a more aggressive craft with better acro capabilities. 

[G+_Paul H]

So I've been doing a little research on what motor I would need. I found a sunny sky 3508 kv380 that looks promising. I'll be using 15" props to achieve the necessary thrust. In the chart it looks like it will pull a max of 12.8A. If I get an esc that will cover that (times 4) does the size of the battery really matter. With respect to damaging the motor I mean.