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Gathering Electronics from scratch


#1

Hi
I would love some help on the motor,esc and battery
I am thinking of buying this motor http://www.hobbyking.com/hobbyking/store/__18126__Turnigy_Aerodrive_SK3_5065_236kv_Brushless_Outrunner_Motor.html

However I am very confused about the ratings. Will this motor always output 1850W (Rated Max Wattage) and draw current equal to 1850/Supply Voltage and then I use this current value to calculate my ESC. Or does the motor wattage output equal 60A(max amps) x Supply Voltage and therefore as it only draws 60A max I only need maybe a 70A ESC

Also I’ve heard people use 125A ESCs but the motor’s max current is only 60A so what is the point of this?

I really appreciate any help!
Thanks very much


#2

The motor wont always give 2.5 horse power, it has a burst rating. The 125amp esc is so it can survive a burst.


#3

Ok
But on general cruising which of the 2 options is correct as ultimately I would like to know what esc to get and what the normal output power will be.


#4

The output of your motor will varry a lot depending on a multitude of variables: rider weight, gearing, wheel size… i think there might be more but that could be it.

Overall that 1850w is the max yes… but we have science somewhere on this forum that shows you are actually never drawing more than like 400w. A lot of people use a motor very similar to the one that you have linked, then they put a 6s battery and the VESC (Vedders ESC) to keep the motor spinning and get a respectable 20mph on average. Again, this can vary based on weight, wheel size… blah blah blah.

put simply: safety. If you get a car ESC from hobby king and get it all set up, you are putting weight onto a motor that was meant for an RC car/airplane… itll do it, but she will get super pissed. Mise’ well have a lot of wiggle room so that you always have that safety ceiling. If you get lipo batteries and have a short… you risk having a nice fire that looks a lot like thermite welding. The only ESC that was made specifically for our boards, both long and short, is the VESC.

If you search around on this forum and check out others builds you will find that a lot of people follow the same pattern, get a VESC, get a LiFe battery (like the space cell) throw on a 36 tooth wheel pulley to some 83mm abec flywheels, throw a 14T pulley to that motor you linked, mount it with one of the many motor mounts out there, strap it all under the board, and ride happily for days. Usually they have two motors no less lol

If you can spend the ~$100 on an ESC get either the VESC or torqueboards 12S ESC. you will have to do some learnings regarless though. have fun!!!


#5

I second on either buying a VESC or torqueboard’s esc.

Torqueboard’s for simplicity

VESC for tinkering

Both are the best options, just for two types of buyers! Good luck on your built!


#6

Hi

If I don’t want to purchase a VESC (high cost) what size amp car/airplane esc would i need.
Is a high esc used just to cope with the burst current upon startup and then when cruising the motor pulls less than 60A and will provide power equal (actually less as it is not 100% efficient) to that current x supply voltage?

thanks


#7

The VESC sits comfortable at a 60 amp draw, but since its made for electric boards you dont need to have that rated comfortable amp draw nearly as high.

Since you are trying to use an RC ESC you will 100% want to ensure that its:

  1. a car ESC as its got breaks typically
  2. can take the beating you will throw at it for making it do something it wasnt 100% meant to do. (a 100+ amp draw, and programmable are the two things that come to mind)

Its like taking a basketball player and telling him to play soccer. Sure he can run up and down the field, probably can even dribble the ball some. But he will really shine when you get him back on the basketball court. An ESC is an ESC yes, but by using a car ESC you will be running a much higher risk of getting the ESC to:

  1. fry itself
  2. give you lots of engine cogging and therefor not a smooth ride
  3. require tinkering to get it to not overheat the motor
  4. pull more power and run less effeciently

the car ESC will work, but the money you save means that you will be researching hard to ensure that you dont end up having to buy 2 or 3 car ESCs (you should just expect to fry one). So, a car esc will work, but you are going to want to put a loootttt of time into searching around online.


#8

That makes it clearer
However i still dont understand why i would need a 100Amp rc car esc. Wont that supply the motor with 100A but then fry the motor as its max current limit is 60A?


#9

look at it this way.
the numbers printed on cheap ESC’s are probably all fat anyway.
a “200A” ESC is probably pretty unlikely to actually reliably handle 200A for any sustained period of time. (if at all)
so by buying a “120A” ESC you are more likely to see an actual 60A current though.

also you wont fry your 60A motor with a 200A ESC. these numbers are purely “ratings” not actual currents. so its not as if you turn on a “200A” ESC and there is 200A coming out the back of it… in fact there’s nothing coming out at all.

the motor actually DRAWS current from the ESC. so its the relationship between the motor and the battery that makes the current flow through the ESC.


#10

Right thanks a lot for that explnation
One thing though, if the motor is put under load I assume it will draw more current. However will the motor keep drawing current until roughly 60A and then just stop turning. Or will it carry on and burn out


#11

the motor is a “dumb” component it doesn’t have any limiters or anything smart… its just a pile of copper and magnets. so it will try to keep going until it burns out.


#12

So do i just have to gear the motor to make sure it doesnt draw more than 60A


#13

60A is a lot of amps. all the motors I have used are 60A max and never blown one.
I think you’ll be fine.


#14

Ok so i just need to buy a 120A rc car/airplane esc only because the amp rating is not entirely correct and probably more like 60A

And the motor realistically wont draw more than 60A and therfore the max power i can expect with a 4s lipo (14.8V) is 60x14.8 W

Is this all correct?


#15

don’t get a plane ESC get a car ESC.


#16

Car esc. Not plane, not boat, not helicopter. CAR.
Another thing to note is you are absolutely going to get out of your board what you choose to spend on it.


#17

With that car RC you wont be able to tell how kuch amperage you are rolling with. Howver 4s is way slow. Do 6s at mins. Im rolling 12s on hills.

The car esc is cheap and thisly dont expect the world of it. It was MEANT for an rc car that weighs maybe 10 pounds. Your board alone will easily get up to 15 pounds. Thusly you make the ESC as beefy as you can so it can handle as much current as you drop through it. Then you just let the motor draw what current it needs. Due to the weight the current will need to do a high amp load for a long period of time (like riding up a hill) so rather than risk frying a component you beef it up. I can guarantee you that if you get a 60a esc for you 60a motor, you will fry your esc and risk shorting out lipo batteries.

My torqueboards esc can do like 180amp continuous and then do 1000amp burst. Ill never get 180 amps to glow through that motor… yet ive already burned through one esc…

If you short a lipo it can explode. I would hate for you to end up frying yourself alive because you wanted to buy the cheapest CAR esc you could find. Get a car esc


#18

Every castle esc I’ve used is still in action except for one). No programming issues. No fault codes, No drv blah blah to replace. And the xe runs and ez runs are pretty much Bomb proof from hobbywing. The only reason everyone here believes differently is marketing for higher voltage setups. And, also note that the torqueboard’s esc is a car esc.


#19

The fact is though, to get a reliable CAR esc you will spend more money on it than on a vesc anyway. And if you cheap out on a smaller boat or plane esc you may hurt yourself.


#20

ok
does anyone have any car ESCs they can recommend or think will probably work?
Thanks everyone