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Mavic Battery and Speed efficiency chart

Andrew F

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My son did a middle school science project using the Mavic. See the attached graph. He (and I) expected a different result. I believe the results very clearly show that at 20 MPH and up to max speed, the battery use per foot traveled is equivalent. Therefore, there is no battery penalty for "coming home" fast (e.g. in sport mode) vs. slower. And, as has been discussed previously, below 20 MPH, you will actually use more battery per foot traveled. The "age old" question of the most efficient speed has been answered - it is 20 MPH or higher. Mavic Efficiency.jpg
 

Andrew F

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My son did a middle school science project using the Mavic. See the attached graph. He (and I) expected a different result. I believe the results very clearly show that at 20 MPH and up to max speed, the battery use per foot traveled is equivalent. Therefore, there is no battery penalty for "coming home" fast (e.g. in sport mode) vs. slower. And, as has been discussed previously, below 20 MPH, you will actually use more battery per foot traveled. The "age old" question of the most efficient speed has been answered - it is 20 MPH or higher. View attachment 12817
This was tested on a 1,500 foot route out and back (for a total of 3,000 feet) to offset any wind effects at 4 MPH increments on both a calm day and a windy day. We used waypoints up to 20 MPH and then flew manually from 24 through 40 MPH (the onboard waypoint software does not allow for sport mode.) We reversed order of operation to offset any battery effects (e.g. we flew the first test at 4 MPH at full battery and then increased speed as battery declined, and the second test we started at full battery and max speed and worked down.)
 

CaveDrone

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This was tested on a 1,500 foot route out and back (for a total of 3,000 feet) to offset any wind effects at 4 MPH increments on both a calm day and a windy day. We used waypoints up to 20 MPH and then flew manually from 24 through 40 MPH (the onboard waypoint software does not allow for sport mode.) We reversed order of operation to offset any battery effects (e.g. we flew the first test at 4 MPH at full battery and then increased speed as battery declined, and the second test we started at full battery and max speed and worked down.)
Good to know and congratulations for a job well done to your son and you.
 

Andrew F

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Good to know and congratulations for a job well done to your son and you.
Thanks. I was truly surprised by the results. Obviously the CD is low enough that 40 mph isn't fast enough to create significant drag. I thought as it pitched forward the CD would increase measurably. Wrong!
 

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Nice one.
How did you establish the mAH used per mission? Was it something like Smart battery % usage on mission, expressed as a % of 3830 mAh battery rated capacity.
 

Andrew F

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The native Go 4 app has detailed battery mAH readings (just click the battery icon) and we noted the values before and after each run. Took a lot of patience at 4 MPH, trust me! It was a blur at 40 MPH. Haha.
 
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Logger

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Well done. Never noticed the mAH remaining readings in there.
Yeah you could have had lunch while it ran the 4mph run I bet.
 

Heisenberg

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Amazing. Good job!

It's a really valuable information, that is going to change the way I fly to get the max distance per battery charge.
 

JoostGT3

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That is quite interesting!
As you expect, flying faster will require more juice and increase drag squared.
Flying faster will also increase any lift, thus reducing the amount of lift required by the props. However, I would assume the lift to be next to nothing with the aerodynamics of a quad... apparently not!

So, going on on that observation, it seems that aerodynamics do play a role in the efficiency.
Could we then improve the aerodynamics to increase flight times? For example by adding a shape at the rear of the body, effectively lengthening the chord of it, yielding more aerodynamic performance?
 

Andrew F

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That is quite interesting!
As you expect, flying faster will require more juice and increase drag squared.
Flying faster will also increase any lift, thus reducing the amount of lift required by the props. However, I would assume the lift to be next to nothing with the aerodynamics of a quad... apparently not!

So, going on on that observation, it seems that aerodynamics do play a role in the efficiency.
Could we then improve the aerodynamics to increase flight times? For example by adding a shape at the rear of the body, effectively lengthening the chord of it, yielding more aerodynamic performance?
I spoke to
Well done. Never noticed the mAH remaining readings in there.
Yeah you could have had lunch while it ran the 4mph run I bet.
too true!
 

Andrew F

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That is quite interesting!
As you expect, flying faster will require more juice and increase drag squared.
Flying faster will also increase any lift, thus reducing the amount of lift required by the props. However, I would assume the lift to be next to nothing with the aerodynamics of a quad... apparently not!

So, going on on that observation, it seems that aerodynamics do play a role in the efficiency.
Could we then improve the aerodynamics to increase flight times? For example by adding a shape at the rear of the body, effectively lengthening the chord of it, yielding more aerodynamic performance?
I understand it is nearly impossible to calculate a CD for a helicopter because of the variable angles and prop wash, etc. Four props on the Mavic and an angular design adds to the complexity. I sure don't see any "lifting body" on it. But would be fun to add.
 

JoostGT3

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Correct. It may have been me who told you :-D
 

Andrew F

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Yes. You too! I consulted with a helicopter pilot and an aeronautical engineer who concurred. Thanks for helping out!
 
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Andrew F

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That is quite interesting!
As you expect, flying faster will require more juice and increase drag squared.
Flying faster will also increase any lift, thus reducing the amount of lift required by the props. However, I would assume the lift to be next to nothing with the aerodynamics of a quad... apparently not!

So, going on on that observation, it seems that aerodynamics do play a role in the efficiency.
Could we then improve the aerodynamics to increase flight times? For example by adding a shape at the rear of the body, effectively lengthening the chord of it, yielding more aerodynamic performance?
I took a closer look at the Mavic and I think it could be argued that the top "curve" might be a lifting body. I thought it was flat, but it is not. As it tilts forward, the lift might actually get a bit stronger. I have no way to prove this, but something has to explain the counterintuitive results.
 

JoostGT3

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I took a closer look at the Mavic and I think it could be argued that the top "curve" might be a lifting body. I thought it was flat, but it is not. As it tilts forward, the lift might actually get a bit stronger. I have no way to prove this, but something has to explain the counterintuitive results.
That was my observation as well... might be a nice add-on for your investigation! :)
 

quick_dry

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I took a closer look at the Mavic and I think it could be argued that the top "curve" might be a lifting body. I thought it was flat, but it is not. As it tilts forward, the lift might actually get a bit stronger. I have no way to prove this, but something has to explain the counterintuitive results.
I'd say 'not in the slightest'.

(Im new to Mavic/DJI so excuse ) does Mavic keep an accessible flight log of the rpm (or amps) of each motor, and the pitch/roll/yaw values?

It'd be interesting to see what happens to the efficiency of the rear rotors above a few degrees of pitch once they see cleaner air versus moving through air that is influenced by the front rotors. (Though that wouldn't say much about being a lifting body - but, Mavic seems to have the aerodynamics of a brick, though at least the arms are narrow and the gimbal doesn't increase cross section from the front)

With that log you could really start to work on why it was happening
 

Kilrah

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I took a closer look at the Mavic and I think it could be argued that the top "curve" might be a lifting body.
Not when it has a negative AoA anytime the aircraft is moving due to tilt...

(Im new to Mavic/DJI so excuse ) does Mavic keep an accessible flight log of the rpm (or amps) of each motor, and the pitch/roll/yaw values?
Yep.
 
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Andrew F

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I'd say 'not in the slightest'.

(Im new to Mavic/DJI so excuse ) does Mavic keep an accessible flight log of the rpm (or amps) of each motor, and the pitch/roll/yaw values?

It'd be interesting to see what happens to the efficiency of the rear rotors above a few degrees of pitch once they see cleaner air versus moving through air that is influenced by the front rotors. (Though that wouldn't say much about being a lifting body - but, Mavic seems to have the aerodynamics of a brick, though at least the arms are narrow and the gimbal doesn't increase cross section from the front)

With that log you could really start to work on why it was happening
Ok. That's it! We clearly need a wind tunnel experiment! Only the smoke will tell the truth! Haha.
 
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