Do bigger motors deliver more torque at the same motor current?

[mutantbass]

Ok not exactly the same but the 140kv has 98milliohm and the 200kv is 46milliohm. So lets say the 190kv motor is 55 milliohm

Turnigy SK8 6354-200KV Sensored Brushless Motor (14P)

Turnigy SK8 6354-140KV Sensored Brushless Motor (14P)

[Gamer43]

Both batteries have a maximum power output of 2400W, thus
The motor amps in the 18s system are 155A
The motor amps in the 12s system are 209A

The 140Kv motor, assuming it does not saturate, produces 10.6Nm of torque at the shaft
This is 507.5N at the wheels
The 190Kv motor, assuming it does not saturate, produces 10.5Nm of torque at the shaft
This is 448.18N at the wheels

The 18s system reaches top speed faster

[mutantbass]

@Gamer43

The motor amps in the 18s system are 155A
The motor amps in the 12s system are 209A

Where are you getting this?

[Gamer43]

I^2 * R = 2400
R = .098 for 18s
R = .055 for 12s

[mutantbass]

Ok What if we used this instead on the 12s and change kv to 260 and gearing to 15/44.

27 milliohm internal resistance.

Turnigy SK8 6354-260KV Sensored Brushless Motor (14P)

[ross_forp]

@mutantbass

The 12s has more motor torque.

False, they’re both the same motors with the same 120a motor current. The motors have the same torque, but if you gear them for the same top speed the 18S wheels have 50% more torque.

[ross_forp]

@mutantbass

They won’t though. 12s can do more motor amps.

False, whether you’re limited by the battery or esc, they can both do the same motor amps— the 18s 2p can do less battery amps than 12s 3p, but they both have the same motor amps.

[ross_forp]

@mutantbass

12s3p set to 60 battery amps, 18s2p set to 40 battery amps. Motor amps on both set to 10000000 amps. Which board is putting more force into the wall?

both the same, unless you gear for the same top speed then the 18s is putting more force.

[ross_forp]

@mutantbass

Why? the 12s system has more motor amps available at any given speed.

you’re confusing more battery amps with more motor amps. they can both do the same motor amps, even if the 18s does less battery amps.

[mutantbass]

@ross_forp

you’re confusing more battery amps with more motor amps. they can both do the same motor amps, even if the 18s does less battery amps.

@ross_forp

both the same, unless you gear for the same top speed then the 18s is putting more force.

@ross_forp

False, whether you’re limited by the battery or esc, they can both do the same motor amps— the 18s 2p can do less battery amps than 12s 3p, but they both have the same motor amps.

I mean at the same speed. Use these setups with 39mph top speed

18s setup

18s2p samsung 30q
140kv motor
100mm wheels
15/36 gearing

battery amps = 40a total. motor amps are setup to 10000000amps.

12s setup

12s3p samsung 30q
190kv motor
100mm wheels
15/32 gearing

battery amps = 60a total. motor amps are setup to 10000000amps.

---

At any given speed/throttle position, 12s setup has 50% more motor amps available.

[rusins]

Both of you guys need to spend less time writing and more time reading and thinking, lol.

Also I agree with Gamer’s results. Because they’re literally just math

[murdomeek]

i read through the entire thread and came out more confused than before.

Thanks guys XD

[mutantbass]

I am waiting on the 12s 260kv results. haha

Its just nit picking at this point. Just go with whatever’s cheaper.

[rosco]

Yup

[fessyfoo]

@murdomeek

i read through the entire thread and came out more confused than before.

I think there’s like a magic trick being played where two simultaneously correct points are being argued and confused against one another.

but I’d have to re-read the whole thread and concentrate to untangle it.

8s > 18s > 12s. for some reasons that all works out… :P. [ stooge 8s reference joke ]

[glyphiks]

My dad is tougher than all your dads.

Fuck HV. 10-12s for life.

Edit: except in a direct drive scenario where obviously higher voltage is more better.

[Vanarian]

Just adding my 2 cents to the topic :

There is also a mechanical relationship between torque output by the motor and its diameter (not talking about it’s length) because of how far tangent force are from pivot point of the motor (its axle).

Picture tiny vectors trying to put your motor can in motion around the axle.

Or picture yourself trying to push open a door. If you’re pushing close to the mounting points where it pivots, you’re gonna put much more effort than if you push the edge of the door near the handle.

Same with your motor

That’s why your typical e-bike motor wipes the floor with your typical e-skate motor at a fraction of the power, bigger motor just doesn’t need as much amps to go rocket acceleration. It’s also more efficient by far

[fessyfoo]

@Vanarian

That’s why your typical e-bike motor wipes the floor with your typical e-skate motor at a fraction of the power, bigger motor just doesn’t need as much amps to go rocket acceleration. It’s also more efficient by far

so you’re saying bigger motor does mean more torque for same amps?

or is it just that ebikes are pushign more watts by more voltage?

[ross_forp]

You could plausibly get 10-12lbs extra thrust at 15mph changing nothing but reducing the motor resistance from 70mOhm to 20mOhm… don’t ask me for all the formulas, lol

[Gamer43]

@mutantbass

I am waiting on the 12s 260kv results. haha

Here are the equations

Max power = battery voltage * battery current
Max motor amps = sqrt(Max power / winding resistance)
Max torque at motor shaft output = max motor amps * motor torque constant
motor torque constant = 60 / (2 π * Kv)
Max torque at wheels = gear reduction * max torque at shaft output / wheel radius (IN METERS)

You’re free to do the multiplications.