New Platinum Props Tested

[CyberNate]

It looks like I burned out 1 of my Esc's. My last flight was fine, which was stock configuration. Today I try to fly and I get "1No.ESC Error" and aircraft cannot take off due to the error. The new props definitely put more load on the motors. Perhaps I damaged it with a previous flight. I did fly with heavy batteries 2 flights earlier, but last 2 flights were stock and I had no issues. Only today when I attempt to do another flight did I get the error.

It may not be the esc. I have to do some testing. It could be the wires leading to my front right motor. A disconnected motor will result in the same esc error. Would make sense as I had no issues during flight. Yesterday I unfold it and get ready to fly and there's esc error. Motor doesn't turn at all as if disconnected when tested in DJI assistant.

Edit: I'm pretty sure it's the motor wires. I see that my modifications for external batteries has resulted in more flexing of the motor wires when bending the arm in. Basically the motor wires are getting folded over completely with each fold of the arm as compared to other legs which the wires are not bend so severely. I'll have to replace that motor arm which is a real PITA because of the antenna wires that are also in that leg.

 

[sar104]

Yes you are! A increase in voltage will result in a increase in motor RPM,at any setting. Ask the racing drone guy's why they run a 4 S lipo as opposed to a 3 S battery! Raising the voltage will increase the RPM of any electric motor. Take a cheap motor (brushed) and use a single C cell battery,then check the RPM! Now add another cell (in series) 2 batterys,and check the RPM again! It will increase in RPM's! Basic electronics. What I would have liked to seen, was a battery with more capacity. PWM does control motor speed (throttle),but a higher voltage will produce a higher speed at any throttle setting.

I should have been clearer - I don't disagree that increasing the voltage will increase the motor speed for any given PWM, but that is because it increases current in the windings. My point was not that RPM is voltage-independent, but rather that it is not current-independent. Your explanation that I replied to earlier made more sense to me than the decreased voltage, increased current theory. Easy to test though, since the parameters are all logged.

 

[dscline]

My point was not that RPM is voltage-independent, but rather that it is not current-independent.

No, RPM is certainly not current independent, because once you put a prop on the motor, RPM is not independent of torque. For a given prop, torque should increase roughly with the square of the speed. So current will too. When comparing to the same prop. But that's not the comparison we're making here. In the "same prop" comparison, we're not talking about two different conditions that produce the same thrust. If it's the same prop, and you increase speed, you're also increasing thrust. But when comparing two props, both producing the same thrust, but operating at different speeds because the blade pitch is different, the overall power should be the same (ignoring any efficiency differences), but the higher speed prop should require less current, and more voltage. The greater pitch is effectively similar to using a taller gear.

 

[sar104]

No, RPM is certainly not current independent, because once you put a prop on the motor, RPM is not independent of torque. For a given prop, torque should increase roughly with the square of the speed. So current will too. When comparing to the same prop. But that's not the comparison we're making here. In the "same prop" comparison, we're not talking about two different conditions that produce the same thrust. If it's the same prop, and you increase speed, you're also increasing thrust. But when comparing two props, both producing the same thrust, but operating at different speeds because the blade pitch is different, the overall power should be the same (ignoring any efficiency differences), but the higher speed prop should require more current, and less voltage. The greater pitch is effectively similar to using a taller gear.

I agree with that except for the final statement. In comparing different props producing the same power, why does it follow that the higher speed prop will require higher motor current? And in post #95 you stated the exact opposite - that the lower speed props should draw higher motor current:

"We know the motors are spinning at a lower speed (if nothing else, just by the tone), so if power is the same, applied voltage will be lower, and current higher."​

 

[dscline]

I agree with that except for the final statement. In comparing different props producing the same power, why does it follow that the higher speed prop will require higher motor current?

Sorry, I reversed my words. I should have said "the higher speed prop should require less current, and more voltage". I stand by my initial post, not the last one. I'll correct it.

 

[sar104]

Sorry, I reversed my words. I should have said "the higher speed prop should require more current, and less voltage". I stand by my initial post, not the last one. I'll correct it.

OK - but that was your second post, not your initial one, which was lower prop speed requires more current. I think that lower speed, higher current at constant power is the correct relationship, since power should be the conserved quantity with different props, power is the product of torque and angular velocity, and torque should be proportional to current.

So in that case, going back to the original question, increased current would be a possible reason for the motors running hotter with the new props.

 

[Dw911]

Standard MP, I was mostly hovering at altitude, checking out the countryside. I usually fly distance flying @ 20-30 mph but either way, these motors were *HOT*!!

Plus, I didn't think they were much if any quieter

bob

Thanks for the reply

 

[dscline]

OK - but that was your second post, not your initial one, which was lower prop speed requires more current.

Ha, yes, I had corrected my 2nd post, but in my clarification to you, I swapped the words, again. I've corrected that. I stil lstand by my initial post.

I think that lower speed, higher current at constant power is the correct relationship, since power should be the conserved quantity with different props, power is the product of torque and angular velocity, and torque should be proportional to current.

So in that case, going back to the original question, increased current would be a possible reason for the motors running hotter with the new props.

Correct, which was my point from the beginning. I just seem to have an issue with reiterating it.

 

[sar104]

Ha, yes, I had corrected my 2nd post, but in my clarification to you, I swapped the words, again. I've corrected that. I stil lstand by my initial post.

Correct, which was my point from the beginning. I just seem to have an issue with reiterating it.

Yes - your initial post about the speed-current relationship seems compelling. Whether or not it accounts for the reports of higher temperatures still needs to be established.

 

[leonardolisboa]

With the new prop you're increasing the pitch, however the motor specs are the same (same KV) that means that it is theoretically capable of performing the same RPM using a higher pitch propeller, where will consume more amps and in consequence will cause more heat to the motor if used in close to its capacity RPM. If the motor or speed controller were not designed to handle this amp level, it will burn the motor/speed or reduce its life as we stress them.

We should verify the speed controller and motor amps specs (not peak, but nominal) and see if it is safe or not to use these propellers in this setup. Maybe the speed change in Platinum was to handle higher amps for longer times.

 

[lolo780]

It may not be the esc. I have to do some testing. It could be the wires leading to my front right motor. A disconnected motor will result in the same esc error. Would make sense as I had no issues during flight. Yesterday I unfold it and get ready to fly and there's esc error. Motor doesn't turn at all as if disconnected when tested in DJI assistant.

Edit: I'm pretty sure it's the motor wires. I see that my modifications for external batteries has resulted in more flexing of the motor wires when bending the arm in. Basically the motor wires are getting folded over completely with each fold of the arm as compared to other legs which the wires are not bend so severely. I'll have to replace that motor arm which is a real PITA because of the antenna wires that are also in that leg.

That's good news. I just converted some of my datalogs with csview and I hit a max esc temp of 103 which seems really hot.

The motor wires are 22ga, so the 16cm front wires should have a resistance of 8.3mOhm each, for a loss of 0.28% at 6 amps. I was looking at rewiring the motors with 20ga tefzel wire, but maybe not worth it yet.
Voltage Drop Calculator

 

[Ron_Dog]

Who Knows? Until we get our hands on the props and run some test,this is all speculation! There are also too many variables,that can effect the outcome! Flying into a head wind will certainly effect the load, placed on the motors,as well as flying with a tail wind will "unload" the motors. I looks like we will need a school gym to hover in,for really accurate results!

 

[BudWalker]

That's good news. I just converted some of my datalogs with csview and I hit a max esc temp of 103 which seems really hot.

The motor wires are 22ga, so the 16cm front wires should have a resistance of 8.3mOhm each, for a loss of 0.28% at 6 amps. I was looking at rewiring the motors with 20ga tefzel wire, but maybe not worth it yet.
Voltage Drop Calculator

I'm pretty sure that's ESC temperature and not motor temperature.

 

[sar104]

With the new prop you're increasing the pitch, however the motor specs are the same (same KV) that means that it is theoretically capable of performing the same RPM using a higher pitch propeller, where will consume more amps and in consequence will cause more heat to the motor if used in close to its capacity RPM. If the motor or speed controller were not designed to handle this amp level, it will burn the motor/speed or reduce its life as we stress them.

We should verify the speed controller and motor amps specs (not peak, but nominal) and see if it is safe or not to use these propellers in this setup. Maybe the speed change in Platinum was to handle higher amps for longer times.

Agreed. Or also it's possible that the firmware change puts a lower motor speed limit with the new props so that it does not draw more current that it was designed for. The Platinum doesn't have significantly higher flight performance specs, does it?

 

[lolo780]

I'm pretty sure that's ESC temperature and not motor temperature.

Yes, ESC temp. After demagnetizing my #1 motor due to heat, I ventilated the under sides and haven't had an issue since. In fact my rear motors are running cooler than the fronts now due to being more open underneath vs the fronts being blocked by the antennas.

I mentioned the motor wires because if an arm needed replacing, it would be a good time to upgrade the wire gauge at the same time.

What we need is a performance graph for the stock Mavic motor to see where each prop lands in various flying situations.

 

[cderoche]

Yes you are! A increase in voltage will result in a increase in motor RPM,at any setting. Ask the racing drone guy's why they run a 4 S lipo as opposed to a 3 S battery! Raising the voltage will increase the RPM of any electric motor. Take a cheap motor (brushed) and use a single C cell battery,then check the RPM! Now add another cell (in series) 2 batterys,and check the RPM again! It will increase in RPM's! Basic electronics. What I would have liked to seen, was a battery with more capacity. PWM does control motor speed (throttle),but a higher voltage will produce a higher speed at any throttle setting.

I wonder if there is a way to squeeze more run time out of the batteries we already have? These things on DJI's site are listed at something like 3830mah but on the battery info screen in DJI Go 4 none of my batteries show anything near that for their capacities, more like 3530mah. And I have 4 packs, none are extremely old, ranging from 20-45 charge cycles. I saw a battery maintainer device somewhere for these DJI lipos - it slow charges them and fully deletes them to "reset" the charge meter / memory etc. It might be snake oil, not sure. Wasn't that cheap, I think $100-150 if I recall. If I can think of the site I'll post it.

 

[cderoche]

Yes, ESC temp. After demagnetizing my #1 motor due to heat, I ventilated the under sides and haven't had an issue since. In fact my rear motors are running cooler than the fronts now due to being more open underneath vs the fronts being blocked by the antennas.

I mentioned the motor wires because if an arm needed replacing, it would be a good time to upgrade the wire gauge at the same time.

What we need is a performance graph for the stock Mavic motor to see where each prop lands in various flying situations.

What did you do to ventilate the motors?

 

[lolo780]

What did you do to ventilate the motors?

This might be a good idea for anyone using the new props.

Official Mavic Range Leaderboard

 

[Steelgtr]

Again, my first test with the new props was not how I usually fly; Hovering on a windy day at altitude vs. long distance flights. So I need to hover with the old props or fly far out with the new ones, I have a P3 and P4 and MP and have never felt motors this HOT!

bob

 

[lolo780]

I wonder if there is a way to squeeze more run time out of the batteries we already have? These things on DJI's site are listed at something like 3830mah but on the battery info screen in DJI Go 4 none of my batteries show anything near that for their capacities, more like 3530mah. And I have 4 packs, none are extremely old, ranging from 20-45 charge cycles. I saw a battery maintainer device somewhere for these DJI lipos - it slow charges them and fully deletes them to "reset" the charge meter / memory etc. It might be snake oil, not sure. Wasn't that cheap, I think $100-150 if I recall. If I can think of the site I'll post it.

I don't think the mAh indicator means much, because I just tested a brand new battery against a 20 cycle one that was showing 35xx capacity. I flew both back to back on wifi (easy and slow circuits) and both produced 25min flight times.