So your battery is running low

[edcMavicPilots]

Everywhere I have have read the recommendation is to return to home in Normal mode, NOT Sport mode. That makes total sense to me. Generally speaking vehicles simply are not as efficient at high speeds as they are at lower speeds for a variety of reasons.

The reason I bring this up is because there is an author on DP Review is suggesting to people that when their battery is low to put it into sport mode and speed back.

Has anybody seen a more scientific test of this testing Normal and Sport mode in the same conditions (wind, altitude, etc) to find out how much distance one can get out of either mode per 1% battery drain.

 

[MAvic_South_Oz]

Normal P mode is the go, there's been test and more tests on the forum here.
It's the same theory as going full pedal down in a vehicle you chew up heaps more 'fuel' for less benefit overall.

There are small ways to minimise battery use.
Turn off OA, although this might just allow faster P mode (?).
If high, use left stick down to bring it down gradually to safe lower level as you come towards home, get the economic descent with lower battery use.

Last ditch scenario, look for an accessible place to land if needed and put it down while you still have 5% or whatever.
Better than a forced landing somewhere not as easy to get to, or terrain is more difficult etc.

 

[MS Coast]

Everywhere I have have read the recommendation is to return to home in Normal mode, NOT Sport mode. That makes total sense to me. Generally speaking vehicles simply are not as efficient at high speeds as they are at lower speeds for a variety of reasons.

The reason I bring this up is because there is an author on DP Review is suggesting to people that when their battery is low to put it into sport mode and speed back.

Has anybody seen a more scientific test of this testing Normal and Sport mode in the same conditions (wind, altitude, etc) to find out how much distance one can get out of either mode per 1% battery drain.

Drag goes up with the square of speed. Twice as fast means four times the drag.

 

[edcMavicPilots]

Normal P mode is the go, there's been test and more tests on the forum here.
It's the same theory as going full pedal down in a vehicle you chew up heaps more 'fuel' for less benefit overall.

There are small ways to minimise battery use.
Turn off OA, although this might just allow faster P mode (?).
If high, use left stick down to bring it down gradually to safe lower level as you come towards home, get the economic descent with lower battery use.

Last ditch scenario, look for an accessible place to land if needed and put it down while you still have 5% or whatever.
Better than a forced landing somewhere not as easy to get to, or terrain is more difficult etc.

Right. I understand all of that but I've tried searching for the empirical evidence of it and don't find any links.

 

[MS Coast]

Right. I understand all of that but I've tried searching for the empirical evidence of it and don't find any links.

I recall finding some measured data a couple of years ago, but it was limited and it was for earlier models. Keep us posted if you're able to find something.

 

[AZDave]

The reason I bring this up is because there is an author on DP Review is suggesting to people that when their battery is low to put it into sport mode and speed back.


Whoever said that is either a moron or a troll. As MS Coast says above, drag increases as the square of the speed, and that applies both to the flight drag on the drone AND the drag on the propellers.

 

[edcMavicPilots]

I recall finding some measured data a couple of years ago, but it was limited and it was for earlier models. Keep us posted if you're able to find something.

I'm thinking I may do a simple test myself but I need to work my way through a practical methodology. Maybe something like flying a pattern even if it is back and forth for 10 minutes in each mode so the distance is the same then log the battery deltas for each.

 

[MAvic_South_Oz]

Lol, had the below typed out and saw your last post . . . here 'tis anyway.

It's going to be somewhat similar (not too indifferent) for most models of aircraft, I'd guess.
The best thing is to test yours, so you know what's best for your aircraft and needs in a particular situation.

Has to be done manually (I feel) for best result.

Find your aircraft's normal RTH speed by testing that in flight.
Do a test on a still day, flying out over a flat area, keep altitude say under 100'.
Either fly out and back, or a triangle / rectangle pattern, something reasonably repeatable, you could fly the route several times to keep it as close as comfortable, but the more allowance for variation of the flight, the less accurate it will be.
Repeat test with a newly charged battery, only fly it in Sports mode.

Or you could do a triggered RTH test this way . . .
You could try a long range test on the home leg using RTH.
Fly out a considerable distance, at 50% exactly set off RTH, note % battery at return.
Repeat the above with a new charged battery, allow RTH and push right stick full forward . . . not sure if this will give you much more speed, but it should give you something to disseminate as compared to the slower speed.

If the above testing in very still air to fairly mild wind go well, you could repeat carefully with a wind blowing.
It's going to possible be different with a strong headwind etc on a homeward leg . . . sports mode might be better to at least make headway more reliably, the possibility of you having to land prematurely is increased though.
I feel it would be best in that case to fly out and back into and with the wind respectively on those flight legs.

Try some of these threads, searched > economical battery flight

Flight mode Vs battery drain.

most efficient MP speed for conserving battery?

Mavic Battery and Speed efficiency chart

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...

mavicpilots.com

Some other search terms might yield more results, these were just quick ones I found.

 

[LoudThunder]

I've tried searching for the empirical evidence of it and don't find any links

If you want "empirical evidence" on just how long you can fly your drone after you've pushed it beyond a reasonable distance and you still hope to get it home then you need to perform the test yourself. You need to do this yourself because the data is based your drone's flight characteristics and your flying methods.

Take two batteries that are as closely matched as possible, number of charges, and voltage when fully charged, then go find a large flying area, bring a lawn chair, and fly your drone around. I would suggest set the drone to Normal Speed and give it full forward and just a touch of Left or Right Roll (by holding the stick at One or Eleven O'clock position, the Drone will just fly large lazy circles (hence the lawn chair…).

As the batteries run down to the 20% level, keep your drone close. As soon as your drone screams, "Bring me home, I don't want to die…" land it and shut the motors down. By restarting the motors, this will establish a new flight, and your app will now keep track of the distance and the flying time separate from the previous flight…

Now, this is all on you, because it is recommended not to run your batteries down to 0%, but you want that "empirical evidence"… Therefore, take you drone back up and continue to fly, still at Normal Speed, and fly it until it goes into a force landing…

Now, go get your drone if you were not able to bring it home and give it a kiss, because it deserves it… Let your drone cool off, have a cool one yourself because you are going to do this all over again…

With a fresh battery, fly the above mentioned pattern again, still at normal speed. And again when the Drone battery is at 20%, and your Drone is again crying, "Please, not again…" Land It and shut the motors down. Once again, this will establish a separate Flight.

Now this time when you take off with the battery at 20%, set your Drone on Sport Mode and fly those same flight patterns but you will be going a lot faster and therefore should deplete the battery much faster and again fly it until it goes into a force landing…

I fly with a WiFi tablet with no internet and I've never tried to bring up the Flight Data Center while in the field. You can try, I do it from home with my tablet connected to the internet.

To get your "empirical evidence," open the DJI Fly App, On the Intro Screen, Tap the Profile Icon (lower left center), Tap MORE (Bottom Left), and that bring use the Flight Data Center. Assuming you did not fly any more since performing your flight tests, the Top Entry will show you the distance and flight time of that last flight on 20% battery, flying in Sport Mode.

The Second entry was the flight running down the battery…

The Third entry is "empirical evidence" for the distance and flight time of that flight on 20% battery, flying in Normal Mode.

So, based on the flying time and flying distance of these two flight; you should be able to determine if flying slower (Normal Mode) for a longer time verses flying faster (Sport Mode) but for a shorter time, give you a greater chance of getting home on a depleted battery.

If you Tap on the actual entry, it will bring up the actual flight telemetry map, the flight pattern, and plays it like a video of your flight. You can even bring up the satellite map and see the actual stick movements as you flew…

As a point of interest, the distance, and the flight time for the second and the forth flights should be very similar… Remember, you were just lazily flying your drone around running the battery down to the 20% level.

Finally, I am sure there are more scientific methods of establishing this empirical evidence, but there is nothing like having the real Proof in the Pudding verses, hypnotically, "The battery should have blah, blah, blah…"

 

[db4476]

Everywhere I have have read the recommendation is to return to home in Normal mode, NOT Sport mode. That makes total sense to me. Generally speaking vehicles simply are not as efficient at high speeds as they are at lower speeds for a variety of reasons.

The reason I bring this up is because there is an author on DP Review is suggesting to people that when their battery is low to put it into sport mode and speed back.

Has anybody seen a more scientific test of this testing Normal and Sport mode in the same conditions (wind, altitude, etc) to find out how much distance one can get out of either mode per 1% battery drain.

Since I do not fly small planes anymore I had to look it up. There will be a speed where total drag is at its lowest level, but increases as you decrease speed/increase speed. In planes, the sweet spot is at altitude X at Speed Y. Hoping some adventuresome soul tests a drone and acquires an empirical dataset.

"Parasitic drag increases with the square of the airspeed, while induced drag, being a function of lift, is greatest when maximum lift is being developed, usually at low speeds. The diagram below shows the relationship of parasitic drag and induced drag to each other and to total drag."

 

[AZDave]

Since I do not fly small planes anymore I had to look it up. There will be a speed where total drag is at its lowest level, but increases as you decrease speed/increase speed. In planes, the sweet spot is at altitude X at Speed Y. Hoping some adventuresome soul tests a drone and acquires an empirical dataset.

"Parasitic drag increases with the square of the airspeed, while induced drag, being a function of lift, is greatest when maximum lift is being developed, usually at low speeds. The diagram below shows the relationship of parasitic drag and induced drag to each other and to total drag."

View attachment 152120

I'm pretty sure that graph for fixed wing planes doesn't correlate very well for copters.

 

[FLDave]

One thing to remember is that the angle of attack for the drone varies greatly as the speed increases; therefore the drag would not be same as level flying. With a fixed wing plane the angle will not change so much so the drag would be relative to speed. For the drone it's different.
Actually, I suspect DJI has some evidence to show the most efficient way to return is a 45-degree tilt at top speed. Check your manual for various ways RTH works.

 

[SoCal2S]

You'll need a lot of tools and repeated tests to get a precise answer under ideal lab conditions, but then the battery health, wind, altitude density, humidity, thermals, and other factors can easily skew the numbers by at least 10% one way or another. Best not to push the battery to the limit if you don't want a recovery mission or damage to your drone.

Personally, I would fly the drone home at the highest speed I'm comfortable with (assuming its top speed is around 40ish MPH, so not FPV drones). The reason is that the additional air resistance difference at 30mph vs 40mph is really going to be a smaller factor than the energy required to stay in the air. There is going to be an optimal speed for most efficient flight, but I doubt even DJI took the time to find out what it is.

 

[db4476]

I'm pretty sure that graph for fixed wing planes doesn't correlate very well for copters.

It's all aerodynamics. Consider a drone in sport mode, the drone tilts causing more drag on the body and props vs a slow steady flight. It would be somewhat difficult to test the drag on a drone out in the wild.

 

[MS Coast]

You'll need a lot of tools and repeated tests to get a precise answer under ideal lab conditions, but then the battery health, wind, altitude density, humidity, thermals, and other factors can easily skew the numbers by at least 10% one way or another. Best not to push the battery to the limit if you don't want a recovery mission or damage to your drone.

Personally, I would fly the drone home at the highest speed I'm comfortable with (assuming its top speed is around 40ish MPH, so not FPV drones). The reason is that the additional air resistance difference at 30mph vs 40mph is really going to be a smaller factor than the energy required to stay in the air. There is going to be an optimal speed for most efficient flight, but I doubt even DJI took the time to find out what it is.

A precise answer is not necessary and useful results can be obtained without complex instruments in a laboratory. And there's no need to push the battery to its limits.

One could make two consecutive flights over a fixed distance with a fresh battery for each, one at maximum speed and one at 50 to 60% of maximum. Comparison of the change in battery voltage would yield a good quantitative comparison of the efficiency of the two speeds.

This would be a good application for a Litchi waypoint mission for control of speed and route. Anyone have the time and interest? The results would be useful to many of us here.

 

[Chaosrider]

You'll need a lot of tools and repeated tests to get a precise answer under ideal lab conditions, but then the battery health, wind, altitude density, humidity, thermals, and other factors can easily skew the numbers by at least 10% one way or another. Best not to push the battery to the limit if you don't want a recovery mission or damage to your drone.

Personally, I would fly the drone home at the highest speed I'm comfortable with (assuming its top speed is around 40ish MPH, so not FPV drones). The reason is that the additional air resistance difference at 30mph vs 40mph is really going to be a smaller factor than the energy required to stay in the air. There is going to be an optimal speed for most efficient flight, but I doubt even DJI took the time to find out what it is.

I think there's merit to this perspective.

The aircraft is going to burn a certain amount of energy just to stay in the air. While hovering, that's 100% of the energy use, ignoring the camera and other small power uses. If you hover, you're not going to get home. As you go faster, you'll use more power, but the fraction of total power use used to get home, relative the power used just to stay in the air, will go up. On the surface, that strikes me as a good thing.

I'd welcome a more formal analysis, but it's not immediately obvious to me that the minimum drag speed, is the maximum range speed.

Very high wind could complicate the calculations a bit. Using the Mini-2 as an example, the max speed in Normal mode is 10 m/s, and the max in Sport mode is 16 m/s. So, if you're flying home into a headwind of 12 m/s, your chance of getting home is zero, unless you switch to Sport mode.

 

[Wild Drone Pilot]

Everywhere I have have read the recommendation is to return to home in Normal mode, NOT Sport mode. That makes total sense to me. Generally speaking vehicles simply are not as efficient at high speeds as they are at lower speeds for a variety of reasons.

The reason I bring this up is because there is an author on DP Review is suggesting to people that when their battery is low to put it into sport mode and speed back.

Has anybody seen a more scientific test of this testing Normal and Sport mode in the same conditions (wind, altitude, etc) to find out how much distance one can get out of either mode per 1% battery drain.

When I almost lost my drone from a low battery
My research as I recall said let it come back on auto pilot for the best battery conservation

 

[edcMavicPilots]

A precise answer is not necessary and useful results can be obtained without complex instruments in a laboratory. And there's no need to push the battery to its limits.

One could make two consecutive flights over a fixed distance with a fresh battery for each, one at maximum speed and one at 50 to 60% of maximum. Comparison of the change in battery voltage would yield a good quantitative comparison of the efficiency of the two speeds.

This would be a good application for a Litchi waypoint mission for control of speed and route. Anyone have the time and interest? The results would be useful to many of us here.

The Litchi idea is a great one. It won't work with my Mavic 3 but maybe somebody will see the idea and get interested.

 

[SoCal2S]

A precise answer is not necessary and useful results can be obtained without complex instruments in a laboratory. And there's no need to push the battery to its limits.

One could make two consecutive flights over a fixed distance with a fresh battery for each, one at maximum speed and one at 50 to 60% of maximum. Comparison of the change in battery voltage would yield a good quantitative comparison of the efficiency of the two speeds.

This would be a good application for a Litchi waypoint mission for control of speed and route. Anyone have the time and interest? The results would be useful to many of us here.

The more quantitative info we have the better, just make sure the testing methods and conditions are mentioned so we can gauge how well it applies.

 

[MS Coast]

Ref: post #15 and a Litchi mission to measure battery usage at multiple speeds over a fixed course using Litchi

I was setting up a Litchi mission to made a couple of runs at max speed and one or two slower speeds, and I was reminded that Litchi can only execute waypoint missions in Normal mode. So let's consider plan B.