Dear all,
i would like to use 4s motors with 6s lipos. Is there any parameter limiting the max dshot rpm to 66%?
I am searching the equivalent to betaflights “Motor Output Limit”. I just found MOT_SPIN_MAX but it did not work as expected.
Thanks for input.
What do you mean with 4s motor. Does it mean that the specification of the motor shows maximum input voltage like a 4s lipo?
Limiting of rpm does not mean limiting of voltage. For example if the motor is trning against a high load it is still not able to reach the rpm limit with full power.
I would like to restrain the motor output value, thus rpm, that goes to the ESC, which, can be pwm-value / D-shot value / etc.
I have 2550kV motors which would burn at 6s. However the intention is to be able to use 4s/5s/6s batteries on a quad with 4s (thus 2550kV) motors. In betaflight it is possible to do this even automatically by plugging the battery.
I could rescale throttle range, but this is not the same as arducopter sees the rpm via bidshot.
If it is not possible - no matter. I just thought i overlooked the corresponding parameter.
It’s not possible and seems a little dangerous to me
Also if you limit the PWM Rate the ESC can give the full power (full voltage) to the motors.
This depends on the ESC and not on the controller or algorthim before.
So also with the betaflight function as you said you risk your motors.
Thanks a lot.
The voltage on the motors is not the problem. However, it works on BF with the quad since a long time. I wanted to convert it from BF to arducopter.
You would have to re-scale a lot more than that with Arducopter. I have a quad that has flown on a 2S Li-ion and a 3S Lipo with 4" props or 5" props and the parameters are very different between these combinations. What you are suggesting is not really practical.
Its interesting that it seems possible on BF.
I agree that limiting the PWM only reduces the rpm and the pulse width to the motor, but to create the simulated ac waveform the voltage will be at full (or very close due to some losses) battery voltage.
Would be interesting to see if BF is just RPM limiting or somehow reducing the actual voltage going to the motor.
Again I still not understand your question or problem, maybe I am to stupied.
What do you mean with 4s motor.
The value 2550kv only shows the number of revolution per minute and per volt.
Another value is the max operating voltage.
Do you mean with 4s the maximum operating voltage or some thing else.
How are your motors connectet to the FC. Normally through an ESC if the FC has no in build ESC.
And if you are using an ESC how you control it with Betaflight. Just with a PWM value like a servo.
If so you also can use such a mode with ardupilot.
If you only will limit the maximum pwm value, I think you can do it with “MOT_PWM_MAX”
I agree, if you change the props (size/blade count/geometry) and thus the thrust of the system. But if you limit the maximum rpm value to a similar one on 4s and 6s, not much should change.
(I have a Rekon7 which flies well on 5s and 6s if you omit high throttle values on 6s. I could quantify the differences in PID params. Tuned for 6s it flies perfect with 5s. The response rate of the 6s lipo is far better of course as it has to deliver fewer amps for the same power)
BF is just limiting rpm aka. maximum PWM/Dshot/Oneshot/etc value send to the ESC. The motor still sees the maximum voltage but the speed of the electromagnetic rotational field and thus the rpm is limited.
In BF you could also have different sets of PID parameter depending on cell count, but this is not important.
However, it is a nice feature, but not important.
Hi
I did it several times to use 6s on 4s motors by limiting the output to the esc to 65% on the esc parameter page of mission planner. I had never an issue with burned motor. Works well
BR
Harald