by johandm_be » Wed Sep 04, 2013 9:32 am
Hi Larry,
Thanks for your reply.
I was setting the throttle over UART (with the DUTY command) so I am certain I put it to 100%.
I found that at lower voltages (for example if I change to a 4S battery with the same parameters) then it will allow higher currents.
for example: for ESC#1 above:
if I tell it "duty 100" with a 5S battery (at 20.25V) then it limits the FET duty cycle at 76%, indicating a current of 6.50A (external power meter shows 7.22A)
if I tell it "duty 100" with a 4S battery (at 15.92V) then it limits the FET duty cycle at 97%, indicating a current of 8.00A (external power meter shows 9.44A)
The parameters I listed above were from the motor database and I think these were calibrated on a 4S battery. I wonder if that is the reason the current limiting is so far off.
Note that prior to this I have flown with different ESC parameters that I calibrated myself on a 5S battery. Those currents were much closer to the limit I set. Initially that had been working fine but at some point my craft crashed and from the logs we determined that one of the ESCs/motors failed. I repaired the craft and put 6 new ESCs + 6 new motors + 6 new props on it. After 2 flights it crashed again with a motor/ESC failing.
After the 2nd crash, I tested all 6 ESCs and motors from the craft and found that one showed a synchronisation problem when throttle went beyond 70%. That was surprising, because: I did test all 6 ESC+motor sets thoroughly with a bench setup prior to mounting them and then all 6 worked fine. And 2 flights later at least one shows synchronisation problems at 70% throttle.
When I put the parameters from the table above in that ESC it works fine again. That is why I am now leaning towards using the values from the motor table instead of my own calibrated numbers. But I am a bit uncomfortable by how much the current is limited with these settings.
Kind regards,
Johan.