New or old motors phantom 3

[Brian T]

Let's throw something else into the mix, an "old" motor goes down, no stock left, do you just swap all 4 for new or do you have to change the esc's as well?

 

[rulppa]

Then the owners of old working p3s thinks it antic, expensive rare piece of art and new version still not worth it

 

[chupeta82]

Let's throw something else into the mix, an "old" motor goes down, no stock left, do you just swap all 4 for new or do you have to change the esc's as well?

u have to swap the esc as well!

 

[gppms]

u have to swap the esc as well!

Complete the central board.

 

[Chadwide]

Hi guys, looks like a lot of opinions running around and nobody's doing the math on this. Since it'sFriday afternoon and I'm just killing time at the office, I thought I'd crunch the numbers. I have quite a bit of experience building my own quads, mostly based on the APM open-source platform, so motor/ESC and propeller matching is something I've done many times.

The new motors spin slower given the same voltage than the old motors (800 RPM per volt versus 960) but the craft still requires exactly the same amount of thrust to hover, and exactly the same amount of thrust to climb at the advertised 5 m/s rate. Because the propellers haven't changed, they'll have to spin at the same rpm to generate the same thrust.

Brushless motors use energy more efficiently as they approach their maximum speed. The RPM needed to make a 1280 gram craft hover with a 9.4” prop with a 5° pitch (DJI 9450 prop found on Phantom3) is 5393 rpm. Because the 800KV motor will be operating slightly closer to its maximum speed when at 5393 RPM, it will be running slightly more efficiently.

I calculate about 30 seconds of additional hover time with the 800KV motors, but in the real world where these motors are operating at a bunch of different RPM throughout a flight, I would expect the flight time difference to be imperceptible.

With the 960KV motors, motor temperatures at max should be about 51°C, but the new 800KV motors would run at about 39°C. At hover the temps are the equal between the two. It should be rare for either motor to get anywhere near max. The theoretical max climb of the 960kv motor is 13.3 M/S and the 800kv is 10.7m/s. Since the flight controller limits this to 5m/s the temps at full climb would be close to the same between both motors. The only place where the motor temp differences would be meaningful would be at full climb and full forward. This would put the rear two motors spinning somewhere towards their max RPM, but I don't have an easy way to calculate what the RPM/thrust would be.

The 800KV motors will make around 3456 grams of thrust at max, and the 960KV motors will make 4352g. If you ever see yourself adding payload to the craft, you might consider the older motors. The reality is, both crafts with the new and with the old motors are well powered.

The 960KV motors were carried over from the Phantom2, and a fully loaded Phantom2 with a gimbal, GoPro, LightBridge etc. can be 1700g. That use case is probably what the 960KV motors were designed for. They're actually probably a bit overkill for the phantom3's sub 1300g weight.

I bet what happened was that DJI was having production issues with the 960KV motor, and set about redesigning it to speed manufacturing. In the process, they figured they might as well reduce output a bit to make it a better fit for the phantom3. Because of the lower output motor would require a greater throttle input to reach the hover RPM, DJI would have had to adjust the target hover throttle rate in the flight controller. The 800KV motors require 49% throttle to hover, and the 960KV motors require 43% throttle to hover (this is because at 100% throttle the 960kV Motors make more thrust).

In order to keep a single firmware version for all the Phantom3 flight controllers, they probably changed the ESC's throttle input signal to output rpm scaling. That's why you need a different esc board.

Anyway, to make a long story short, I seriously doubt there is any flight time benefit, but the lower motor temps look nice…

All my calculations are done in the eCalc (eCalc - xcopterCalc - the most reliable RC Calculator on the Web) if you're interested in learning more about this type of tuning.

 

[Oso]

Hi guys, looks like a lot of opinions running around and nobody's doing the math on this. Since it'sFriday afternoon and I'm just killing time at the office, I thought I'd crunch the numbers. I have quite a bit of experience building my own quads, mostly based on the APM open-source platform, so motor/ESC and propeller matching is something I've done many times.

The new motors spin slower given the same voltage than the old motors (800 RPM per volt versus 960) but the craft still requires exactly the same amount of thrust to hover, and exactly the same amount of thrust to climb at the advertised 5 m/s rate. Because the propellers haven't changed, they'll have to spin at the same rpm to generate the same thrust.

Brushless motors use energy more efficiently as they approach their maximum speed. The RPM needed to make a 1280 gram craft hover with a 9.4” prop with a 5° pitch (DJI 9450 prop found on Phantom3) is 5393 rpm. Because the 800KV motor will be operating slightly closer to its maximum speed at when at 5393 RPM, it will be running slightly more efficiently.

I calculate about 30 seconds of additional of flight time with the 800KV motors, but in the real world where these motors are operating at a bunch of different RPM throughout a flight, I would expect the flight time difference to be imperceptible.

With the 960KV motors, motor temperatures at hover should be about 51°C, but the new 800KV motors would run at about 39°C. The temperature differences get smaller as you start to add more thrust in order to move the craft through the air.

The 800KV motors will make around 3456 grams of thrust at max, and the 960KV motors will make 4352g. If you ever see yourself adding payload to the craft, you might consider the older motors. The reality is, both crafts with the new and with the old motors are well powered.

The 960KV motors were carried over from the Phantom2, and a fully loaded Phantom2 with a gimbal, GoPro, LightBridge etc. can be 1700g. That use case is probably what the 960KV motors were designed for. They're actually probably a bit overkill for the phantom3's sub 1300g weight.

I bet what happened was that DJI was having production issues with the 960KV motor, and set about redesigning it to speed manufacturing. In the process, they figured they might as well reduce output a bit to make it a better fit for the phantom3. Because of the lower output motor would require a greater throttle input to reach the hover RPM, DJI would have had to adjust the target hover throttle rate in the flight controller. The 800KV motors require 49% throttle to hover, and the 960KV motors require 43% throttle to hover (this is because at 100% throttle the 960kV Motors make more thrust).

In order to keep a single firmware version for all the Phantom3 flight controllers, they probably changed the ESC's throttle input signal to output rpm scaling. That's why you need a different esc board.

Anyway, to make a long story short, I seriously doubt there is any flight time benefit, but the lower motor temps look nice…

All my calculations are done in the eCalc (eCalc - xcopterCalc - the most reliable RC Calculator on the Web) if you're interested in learning more about this type of tuning.

Outstanding. Thanks for posting.

 

[Chadwide]

Updated the above with more thoughts on motor temp. On another topic, I have a theory about the 7% greater efficiency that DJI claims for the newer motor. These motors are operating at about 86% efficiency at optimum conditions, so gaining another 7% would get you a Noble prize. What they probably mean is "reduced inefficiency by 7% in some circumstances" Lets say we are operating the motor at 100watts. 14watts is wasted as heat. They probably reduced this waste by 7%. That would be about 1% greater total efficiency, which is at least feasible. It's also is in the ballpark of my results above, where I calculated about 30 seconds of additional flight time out of the newer motor.

 

[Meta4]

Let's throw something else into the mix, an "old" motor goes down, no stock left, do you just swap all 4 for new or do you have to change the esc's as well?

Not an issue - you can still buy motors for P1s and P2s

 

[Zone 5]

It would be interesting to see how the Phantom would fly with the new motors and the old main board/ESC's. In general terms, all the ESC's do is control the amount of volts going to the motors so in theory they had to make the new motors spin faster (more volts) to do the same speed, climb etc as the old, as they didn't change props or the battery amps/volts

 

[phantom13flyer]

The differences between the 2 motors is more noticeable when running an extra 2600-4800 mah.

 

[jamesb72]

I understood the old motors had active braking which slightly improves hold but uses a little more power. My guess is esc firmware is different for this hence old/new control board. DJI supposedly changed motors so they are uniform across range (the new P3A/P motors were already on the P3S), so it was purely a manufacturing/cost reduction change for DJI.

800kv vs 960kv is lower RPM with no load, but if they have altered windings etc to give more torque, they could well produce same RPM/thrust at lower current draw, possibly at the expense of max thrust, but climb has always been limited by flight controller anyway (to a certain climb rate), so you probably never hit max power output anyway (unless flying at high altitude which is restricted anyway, so only applies to people flying from mountain tops etc).

I got a great deal on p3pro with old motors (new shell though) so I just bought spare cw and ccw motors to keep on hand in case i need to swap a motor (they are really cheap). I had two p1s and motors never wore at all so don't expect to need spares but umbrella theory works for me, so I am covered just on the off chance a motor has a problem, I can easily just swap it out.

 

[Chadwide]

The 800kv motor could make more torque, but it's not going to produce that torque unless you increase the pitch of the prop. I can't see them doing it as the craft doesn't need more thrust. If you had more pitch you could lower rpm a bit as you'd move more air per revolution. Their would be an efficiency gain on paper, but it would be tiny in terms of real world benefits.

These crafts are already pretty efficient. There's just no way that there is meaningful amounts of battery life to be gained by changing up the motor. This stuff isn't rocket science and if they could have got another couple minutes with a different motor/prop combo they would have done it on first release.

 

[jamesb72]

If the 800kv motor makes more torque it will hold RPM under load better even for same prop/pitch.

Like going up hill in a lower gear is faster than a higher gear as engine can hold RPM, but on the flat a higher gear is faster.

An example is the emax FPV racing motors, the MT1804 2480kv motors actually spin slower and make less thrust than lower KV MT1806 2280kv motors when both run 3S on 5x3 props - lower kv in that case is more rpm/thrust/efficiency in actual use as the bigger motor makes more torque. The new 800kv P3 motors _could_ be the same, if they have adjusted windings to make more torque at lower kv, which is certainly possible as kv is a trade off between rpm and torque.

Also don't forget the Phantom 3 never actually gives you full throttle/power anyway, top stick is just a certain climb rate - so motors could actually only ever get to 80% and you would never know, so a more efficient lower kv motor could give same apparent performance unless you add weight or fly at high altitude (thinner air/more work for lift).

Personally I don't buy the 2 minute extra flight time efficiency claim, I think the new motors are just cheaper to make/easier to standardise across all models for DJI, and there was a chance the active braking was exacerbating the frame cracking but that's just my hunch, and certainly nothing I have any concrete evidence for

 

[GadgetGuy]

Everyone is focusing on the motors and the flight times. One overlooked factor is that the P3P's with the new motors have from 18% to 28% less video transmission power output than the original P3P, according to the FCC specs for each. This means the video reception will drop out at 18-28% closer than the video range of the original P3P, depending upon which version of the new motor P3P it is being compared to. Each successive version of the P3P has reduced the video power transmission further. This has nothing to do with the motors, but if maximum video range is important, the P3P with the original motors still vastly outperforms the video range of any version with the new motors.

 

[DeeX]

Everyone is focusing on the motors and the flight times. One overlooked factor is that the P3P's with the new motors have from 18% to 28% less video transmission power output than the original P3P, according to the FCC specs for each. This means the video reception will drop out at 18-28% closer than the video range of the original P3P, depending upon which version of the new motor P3P it is being compared to. Each successive version of the P3P has reduced the video power transmission further. This has nothing to do with the motors, but if maximum video range is important, the P3P with the original motors still vastly outperforms the video range of any version with the new motors.

Do you have a link to this information?

 

[GadgetGuy]

Do you have a link to this information?

Check the FCC filings, links below, and my summary below them.

FCC ID SS3-WM3231503 by SZ DJI TECHNOLOGY CO., LTD for Phantom 3 Professional output wattage .745 - April 2015
FCC ID SS3-WM3231507 by SZ DJI TECHNOLOGY CO., LTD for Phantom 3 Professional output wattage .612 - July 2015
FCC ID SS3-WM3231510 by SZ DJI TECHNOLOGY CO., LTD for Phantom 3 Professional output wattage .52 - November 2015
======
Difference in Power Outputs on DJI Transmitters and Aircraft:

The GL300A controller has a frequency range of:
(2404.00000000 - 2480.00000000 and a power output of 0.038000 )

The GL300B controller has a frequency range of:
2404.00000000 - 2480.00000000 and a power output of 0.0380000

The GL300Ccontroller has a frequency range of:
2404.00000000 - 2470.00000000 and a power output of 0.3030000 .

The W323 Phantom 3 Professional has a frequency range of:
(2406.50000000 - 2476.50000000 and a power output of 0.7460000 )
FCC ID: SS3-WM3231503
2406.50000000 2476.50000000 0.7460000

The W323A Phantom 3 Professional has a frequency range of:
2406.50000000 - 2476.50000000 and a power output of 0.6120000 (82% of the W323)
(18% more than W323B)
FCC ID: SS3-WM3231507
2406.50000000 2476.50000000 0.6120000

The W323B Phantom 3 Professional has a frequency range of:
2406.50000000 - 2476.50000000 and a power output of 0.5200000 (70% of the W323)

Both the GL300C and W323C have less power output for control and video transmission signals than the original GL300A and the W323 P3P.

My own experience also confirms the loss of video control distance on the new motor version over the old motor version, even though flight times have increased by a minute or two. Video feed becomes unstable about 20% closer than with the original old motor aircraft. Frustrating.

 

[DeeX]

Your thinking is too linear. Radio doesn't work in linear calculations.

Transmitter power is only one of the dozens of factors that go into RF propagation calculations. Other factors include distance, altitude, fresnel zone interference, free-space loss, cable and connector losses, antenna efficiency and receiver sensitivity.

Since we're digital, the signal is either there or not. There is no in-between. Calculating radio range is serious equations, explanations, tutorials and other brain-hurting material from people who really know their stuff. (I spent a whole semester on this subject). The rule of thumb for all digital wireless systems is have at least 30% more power than you need with a minimum of 5 - 10 dB. This is called the System Operating Margin (SOM).

The difference in the SOM from 520mw to 746mw is negligible. It is from 12dB to 13.57dB according to calculations on Radiolabs.com and assuming everything else is constant. The difference in range would be measured in inches.

Found this post on another thread....
Can anyone else confirm and compare the new with the old and say for certain that the video control distance is much less with the newer versions?

 

[GadgetGuy]

Found this post on another thread....
Can anyone else confirm and compare the new with the old and say for certain that the video control distance is much less with the newer versions?

I read that myself, too, and while I respect Steve's opinions, lowering the output power on both devices certainly does not help with video range. With a battery mod and the FPVLR V2 transmitter mod, with my original P3P with old motors, I was reliably maintaining video at 5 miles. Now, with the new motors and reduced video power, the video starts consistently breaking up at less than 4 miles. I can't explain it any other way. I've even explored a bird side video amplifier, but I have been told that it leaves no room for supplemental batteries, so it defeats the purpose for me. I wish I could buy another new bird with the original motors to regain the original 5 mile video range. Unfortunately, I can't find anyone that still has any for sale, including DJI.

 

[DeeX]

So if I bought one from B&H, Adorama, or Amazon they all will be the new new new ones?
Thats pretty crazy you were able to get video at 5 miles.. Im a Phantom noob but that sounds amazing to me lol.

Do you mind pointing me in the right direction as far as the battery mod and the FPVLR V2?

Thanks!

 

[GadgetGuy]

So if I bought one from B&H, Adorama, or Amazon they all will be the new new new ones?
Thats pretty crazy you were able to get video at 5 miles.. Im a Phantom noob but that sounds amazing to me lol.

Do you mind pointing me in the right direction as far as the battery mod and the FPVLR V2?

Thanks!

Trust me, if I could find one at any of the above, I'd buy it in a heartbeat. All the major distributors turn over their stock relatively quickly. Any remaining old motor inventory was likely cleared out in December. I'm sure there are units out there somewhere in the channel, but I have no way of finding them. If anyone knows of any, I'm all ears!

Paul at FPVCustoms.com can set you up with both mods. I can still get video at 5 miles, but it is now unreliable at low altitude beyond 3 miles, and frequently drops out, messing up the video recording, as you can't frame a shot you can't see, and flying blind is not my cup of tea! I used to be able to maintain video feed at 100 feet over water 5 miles away, but now often have to climb to 400 feet, when the subject requires a water level shot. Could have just been a unique bird, but the FCC spec changes are significant. I have also been told that there is no assembly consistency within the versions as to whether the two birdside video antennas in the legs are both installed on the same side (where the gimbal could potentially block both) or are placed on diagonally opposite sides (better overall, because one side would always be unblocked).