Electric Skateboard Calculator | ESK8 Calculator - What size, Motor, Battery, Wheel, Belt to use?

Hey hey @Kug3lis thx for the great new calc :+1::+1: So the range calc is correct? Do i need to select 1wd even when i got a dual system ir not? Kr

Range calculator depends on your average Wh/km 1wd is for single drive, 2wd is for dual motors and 4wd is for 4 wheel drive.

Average Wh/km I took from old calculator its how much one motor consumes power so the range is calculate Battery Wh / (Motor Count * Avg Consumption)

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Ok got it thx

Feature request: acceleration!

Or rather, since everyone’s weight differs, force of acceleration, calculated from the max torque and wheel diameter. F = torque / radius. That way people can mix and match combinations to find a suitable one for their desired acceleration.

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Wouldn’t a=f/m work too? I honestly have no idea that’s just how I’ve been shown got to calculate acceleration from force (Nm) and individual mass (kg)

Using that formula my acceleration (m/s^2) would be a =16.2/60

a = 0.27m/s^2

What’s yours?

Edit: Idk if the max torque shown is wheel rotational force or forward movement. Now I think I get why you used that equation. Would you need to do that one before doing the equation I did?

Any input :thinking:

Because higher voltage means less current needs to flow to reach the same amount of watts. Thus less current means less torque. You must adjust the watts up to the new amount based on your voltage :slightly_smiling_face:

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Ah, so if I was planning for 30a on each motor for 10s, would you recommend 35a on 12s?

I was speaking to @deucesdown and (please, anyone, if I’m wrong, don’t heckle deuce) he made a comment where range seems to benefit off of increased series numbers, but wouldn’t the need to readjust the values to achieve the same amount of torque effectively negate the effect of increasing the series number?

Thanks for the answer Pat

It’s only on this calculator that you must adjust the watts because the max current is not something we can just enter it is calculated from max wattage and pack voltage.

In the vesc tool however you just enter 30a and it will only pull 30a

Example

2000w /36v = 55a

2000w/44.4 = 45a

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Roger Roger, thank you

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Just added an example, hope that makes it crystal clear

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Oooh

Cool, ok. I had it inversed in my head :stuck_out_tongue:

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Looks like I got into your head. :slight_smile: I was referring to this specific post:

Please don’t take it as a broadly general thing. I don’t understand what’s happening, but in this specific instance,

  • adding 4 cells (12s4p → 13s4p, 8% more cells) increased range 29%
  • adding 17 cells (12s4p → 13s5p, 35% more cells) doubled the range

It’s hard to generalize this, and 12s is already a bit risky so it’s hard to recommend 13s.

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Yeah, changing wheel size doesn’t change the torque value in the calculator, so I guess it’s rotational torque that’s being shown. So yeah, you would first need to divide the torque (Nm) by wheel radius to get the force pushing you forward (N), and then you divide by your mass to get acceleration.

My stats: Torque: 12Nm Radius: 42.5cm Acceleration force: 28.24N My weight: 80kg Acceleration: 0.353 m/s^2 Edit: Actually acceleration force is 282.4N, and acceleration is 3.53 m/s^2

:thinking: which means I’ve made a mistake somewhere, because that is super low.

Another thing I noticed is that the torque displayed in the calculator doesn’t change when you change your battery cell discharge rate, which is bad. Means the max motor wattage is used, even if your battery cannot drive them at that rate. However, I guess that’s OK, because I’m guessing just from max W and KV alone (+ motor efficiency) it calculates the motor torque per amps, and when starting from zero voltages are low, so you’ll be able to drive enough amps easily.

If what I’m saying is true, then I guess you’ll have good startup acceleration irregardless of what battery you have – what matters is motor wattage (well, torque, but usually correlated) and your drive train ratio. Would love for someone to either confirm this or correct me :smiley:

I think you got the wrong wheel radius, well unless you use 850mm wheels

Mine is about 2.75m/s/s with 97mm wheels, 16Nm torque and 60kg mass

Edit: I think the wheel radius also must be used in Metres so mine was 0.097m

Yup! That’s where I messed up. Thank you! Now I get 3.53 m/s^2, which seems correct to me.

Everything needs to be in base units, yes

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Why does it say a 12S8P will have less torque then my current 10S4P?

12S8P - 13.8nm after reduction

10S4P - 16.6nm after reduction

When I increase motor max wattage from 3250, the torque goes up as expected. But right now on 10S4P I’m not even pushing 2880+W at 10S-80A battery max(40A/40A)… Which, with voltage sag under full load and charge down to 36 volts, that’s expected- 36v*40A=1440W *2 = 2880W.

By increasing to 12S8P and pushing 120-160A battery max (60-80/60-80), that would be 43.2v(nominal or full charge under load w/sag)*60A = 2592W *2 = 5184W.

How is 5184W less torque than 2880W, from just going from 10S to 12S?

Would it make more sense to be able to input your intended vesc battery and motor max/min values to calculate this better?

What it seems like though, is that the calculator is taking the motor max wattage and not multiplying it by however many motors you have, instead setting a hard wattage limit regardless of number of motors entered.

Then again, if I enter 9999999999 on the motor power rating, the torque goes up to some craaaaaazy number… Shouldn’t the torque be based off your battery max, with the motor rating * # of motors being the absolute wattage limit, and calculating primarily based off your battery and efficiency, with the motor rating acting as a ceiling?

Yeah, the calculator just assumes the max current your motor can handle is watts divided by voltage of your battery. It is very misleading imo. @Kug3lis, please fix :smiley:

P.S. Would be nice if motor kV didn’t have to be a multiple of 10. TB direct drive is 75kV, so it would be useful to enter such values.

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What formula do you suggest it should use instead?

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