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The "Is My Math Right?!" Thread


#1

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#2

This is a great idea and i really hope it resolves the issue in a way that works for everyone.


#3

Your input is welcome and appreciated, you just don’t have to write the same thing 50 times in a thread. Doesn’t talking heads sing about this “say something once… why say it again?” And I appreciate the bold text actually it does make stuff easier to read.


#4

Then i have a math question here. When i have a resistance of 0.016 and a maximum duty cycle of 95%. What is the highest duyty cycle for the motor where it still can produce 1440 watts. And let’s say that the battery is at that moment at 36V and 40A = 1440 A.


#5

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#6

Your right, sorry. My question was wrong.
I meant what is the highest no load motor voltage (no load duty cycle) at which i still can achieve 1440 watts at 95% duty cycle.
For example at a standstill the motor has a no load voltage of 0V. And we feed i with some volts and amps to achieve 1440 W at a stand still.
But now i want to know at which no load motor voltage i still can achieve 1440 watts when my maximum duty cycle with that i can feed the motor is 95% (34.2V).
My calculations tell me that this is somewhere around 92,33% duty cycle (33,24 V) but that seems to be wrong.


#7

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#8

When the motors no load is already at 95% duty cycle and you power the motor with 95% duty cycle then the power output is 0 W. Think if a ideal world without any resistance. The means when you spin the motor with 1000 rpm then it will spin forever with that speed.
A 100 kv motor will spin at 95% (32.4 V) no load with 3240 rpm. When you power that motor now with 32.4 V it won’t spin any faster. You remember the donkey/carrot picture. So in this scenario the donkey reached already the carrot.

My question is now at which no load duty cycle (actual motor speed) you can still get a power output of 1440 W when your maximum duty cycle is 95% (32.4 V). Because when the motor spins already at 94.9 % duty cycle you can’t achieve 1440 watts anymore (at least not when you have a realistic resistance).


#9

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#10

Correct. But lets imagine that the motor spins at no load with 94 % duty cycle. And now we want full power and feed the motor with 95% duty cycle.
So my question is at which no load can i still achieve 1440 watts when i fed the motor with 95% duty cycle.


#11

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#12

That’s not a answer to my question. You repeat what i explained already.


#13

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#14

Pack V = 36V, Ohm Resistance = 0.016, Batt = 1000 /Motor = 1000 /Absolute Max = 2000 Amp Limit Settings, and Motor KV = 190


#15

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#16

Me too
10 chars


#17

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#18

:joy: we all can sing a song about it


#19

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#20

I just experienced that the power output at higher speeds gets less the more resisance the motor has. But on the other side the motor has more torque at very low speeds of you limit the motor max to for example 50 A.
So at low speeds the motor max plays a role. But at close to 95 % duty cycle the motor max can’t even be reached.