torque pickup effect?
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Itâs a well known thing where you get more torque as you speed up with vesc despite the same throttle setting. It was really bad on older versions where you basically had no startup torque.
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tx.
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From the electronics standpoint, Iâd only go for bigger motors to have more thermal mass and thus better performance due to lower temps/thermal resistance offset at high heat. If thereâs space on the trucks, why not go for bigger cans⌠usually the price jump isnât that big.
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While accelerating, at first acceleration will be limited by the motor current setting then at higher speeds acceleration will be limited by the battery current setting.
Acceleration with a larger, same kv motor (assuming it has lower electrical resistance), will be the same on both motors at lower speeds while youâre limited by the motor current setting, but at higher speeds when you are limited by the battery current setting, the larger motor will get better acceleration, because itâs receiving more motor current for the same battery current with the same settings.
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I am not an electrical engineer yet, but from my understanding, I donât think that would be the case, as the control mode everyone uses on the VESC is current control⌠Current can be controlled, by changing the resistance of the system. With a motor of 50 mOhm resistance, at 12S full charge, 1000A could flow through the motor if the ESC had zero resistance. I am not sure how exactly current control works (how exactly the ESC changes resistance) but I donât think the lower resistance of a larger motor could help in any meaningful way.
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Well if both motors receive the same motor current, the lower resistance motor will be drawing less battery current. That also means for the same battery current, the lower resistance motor will receive more motor current and so have greater acceleration.
The esc doesnât change the resistance it changes the voltage.
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Ah, right, that makes sense.
But if both motors are the same KV running at the same RPM then you would expect them to be driven at the same duty cycle right?
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No, the lower resistance motor will have lower duty cycle at the same kv, motor current and rpm.
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Lower resistance motor will need less voltage to hit the target current. This will result in lower duty cycle. Which I guess in theory results in less battery current. Seems to make sense.
âFor the same battery currentâ so what your saying here is if you increase the battery current (which increases total power and therefore increases motor current) then you will have better acceleration. Yes, of course if you use more power you will get better acceleration.
This is not proving that bigger motor give you more acceleration at the same motor current, itâs just showing that low resistance motor is more efficient.
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Right, you wonât get more acceleration for the same motor current, but you will get more acceleration for the same battery current, and at higher speeds youâre actually being limited by the battery current setting not the motor current setting, so it will essentially feel like the bigger motor gives more acceleration above a certain speed with the same settings.
Honestly, anyone that believes that bigger motors give you more power is a fucking idiot. What you are essentially claiming is that you have discovered free energy. Ridiculous.
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The smaller, higher electrical resistance motor generates more heat for the same motor current via I^2R losses. This higher heat but same mechanical power with the smaller motor requires more battery current (but the same motor current) for the same acceleration.
Essentially the bigger motor needs less battery current for the same acceleration because it is running cooler.
But if you instead use the same battery current for both motors, the larger motor will accelerate quicker, because the smaller motor is wasting more of that battery current as heat coming out of the motor.
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Bigger motors can handle more current. Thats a very different thing to saying bigger motors give more power.
This forum is more nuanced so I am mostly talking about facebook idiots who say they went from 6354 to 6374 and got more power. My favourite is people moving between same stator size motors with an extra bearing and claiming more torque. Lol.
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Bigger motors can not only âhandleâ more motor current, but they also produce less heat for the same motor current, on account of their lower electrical resistance.
Less heat on account of lower resistance requires less battery current for the same mechanical power and motor current.
Giving both motors the same battery current, the larger, lower electrical resistance motor will have higher motor current and mechanical power, because the heat produced by the I^2R losses is less in the bigger motor for the same motor current.
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Negligible between 6354/6374/6384/63100. Anyone claiming they can feel that under their feet has drunk the cool-aid. Same people who think 18s is somehow better than 10s/12s. Nonsense in any practical sense.
The 18s will give you 50% higher top speed than the 12s.
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Not so fast. Top speed is a function of
voltage
gearing
motor kv
wheel size
A 12s setup for the same top speed and total output watts as an 18s will have zero perceptible difference. You might need slightly thicker wires on the 12s and maybe a $10 heatsink on the Vesc but there is no free lunch.
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Where do you take your trash out to? Just curious
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