Mavic Battery and Speed efficiency chart

[JoostGT3]

Anybody have a windtunnel?

 

[mavicn00b]

I think flying it 0-15MPH is probably your newbie flyer or someone taking photos of scenery and keeping the drone nearby. 20+ And its more of a joyflight. I found in sports mode that while I only did get approx half the battery, it covered the same distance in that time so closely aligns with the data posted in the graph. Main thing is to look at the RPM count when flying, the higher RPM, the higher the draw. Flying into a headwind will chew more battery for same distance, coming back via tailwind and you gain some efficiency as the motors dont need to work as hard.

 

[adiru]

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

Hmmm so there is no way for Litchi to go faster than 33mph? It seems for long distance BVR flights, 40mph is best speed

 

[Andrew F]

Hmmm so there is no way for Litchi to go faster than 33mph? It seems for long distance BVR flights, 40mph is best speed

I have never used Litchi. I just used the Go 4 app which was limited to non-sport mode.

 

[Logger]

For clarification - Litchi will happily fly faster than 33mph all the way up to the max ~41mph, provided you are not in Waypoint mode. I suspect the limit of 33mph when Litchi waypoint flying is imposed in the firmware by DJI and is nothing to do with Litchi. I just fired up DJI Ground station Pro and it also maxes out WPT flight at 33.6mph.

In any case, did I miss something or wasn't the result of the test - "..that most efficient speed <snip> is 20 MPH or higher."
Therefore @adiru for long distance flights, any speed in that 20-40 range would be equally best speed in still air.

 

[adiru]

For clarification - Litchi will happily fly faster than 33mph all the way up to the max ~41mph, provided you are not in Waypoint mode. I suspect the limit of 33mph when Litchi waypoint flying is imposed in the firmware by DJI and is nothing to do with Litchi. I just fired up DJI Ground station Pro and it also maxes out WPT flight at 33.6mph.

In any case, did I miss something or wasn't the result of the test - "..that most efficient speed <snip> is 20 MPH or higher."
Therefore @adiru for long distance flights, any speed in that 20-40 range would be equally best speed in still air.

For long distance flights, battery being the rate limiting factor, in windy conditions it is even more important to go faster. I would imagine the windier, the faster one needs to fly to get optimal efficiency.

 

[stratos]

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

For the rest of the world. Is there a chart with proper metrics in Meters and KMs ?

 

[adiru]

For the rest of the world. Is there a chart with proper metrics in Meters and KMs ?

No need, in the context of the mavic, faster is always better.

 

[Logger]

For long distance flights, battery being the rate limiting factor, in windy conditions it is even more important to go faster. I would imagine the windier, the faster one needs to fly to get optimal efficiency.

No you are misreading the results. At any speed above 20mph the Specific power consumption is a constant 0.10 mAh per foot. This is regardless of speed withing the 20-40 range. ie the rate per foot is constant.

In windy conditions it will depend if you are going upwind or downwind. Fly upwind fast and downwind slow will theoretically maximise efficiency.

 

[adiru]

No you are misreading the results. At any speed above 20mph the Specific power consumption is a constant 0.10 mAh per foot. This is regardless of speed withing the 20-40 range. ie the rate per foot is constant.

In windy conditions it will depend if you are going upwind or downwind. Fly upwind fast and downwind slow will theoretically maximise efficiency.

He tested in still conditions/ no wind.
In any constant wind conditions, faster is still going to be better, all the way up to Mavic's top speed. At every wind speed. I've done enough long range flights to intuitively know this without seeing his charts.

On a rare day in which at different altitudes the wind changes directions in opposite ways, then fly outbound at the lower altitude layer and inbound on the higher altitude layer, in both cases always flying downwind and at maximum possible speeds. This will get you max total distance. Usually in Litchi I plot curved instead of straight waypoints, since Litchi stops/pauses at straight waypoints (wasting time and battery) and you always want to make sure the Mavic is always heading pointed directly in the direction it is actually headed at any point in time, because otherwise it really slows it down big time if the Mavic's head is pointed at an angle different from its actual track (which can happen even in no wind conditions if you did POI and had it look at something else) and it goes without saying you want to match the wind direction as to avoid crosswinds. Litchi has a bug where sometimes it doesn't want to go max speed set in the cruising setting or custom waypoints. For example you can do in the browser desktop using Litchi hub and create a mission setting everything to 33mph, but when you load it in your phone or tablet, it defaults to max of 16mph and you have to manually tell it to do 33 mph. Even then it won't do 33 mph, and once the mission starts you manually have to immediately increase speed manually to the max allowed and hold it down until it loses RC contact, because at point of signal loss whatever your speed was at that time, will be your (max) speed throughout the rest of the flight. And so its important to set the critical battery percentage to the 10%, otherwise it will be too conservative and RTH early without completing the mission even though your calculations on the numbers are good (which isn't possibly anymore in firmware higher than 400 btw) The reason I typically fly the higher alt on the way back is because it for some reason the Mavic needs to be closer in distance to require signal than the distance at which it lost signal, so it gives you more time to take manual control and go sports mode and bring it back at the maximum possible speed rather than the Litchi's 33 mph max.

 

[Logger]

No it isnt. Look at it like this.
Mavic battery is 3830 mAh. Assume you want to land at ~%10. So we have 3447mAh usable. For simplicity we will call that 3500 mAh. Divide that by the figure of 0.10 mAh per foot specific range as determined by @Andrew F. That gives a still air practical range of 35,000' or 6.6 miles at any airspeed between 20 and 40 mph.

Now fly that distance of 6.6 miles at two speeds, 20 and 30 mph to see how long the battery lasts.

At 20mph airspeed battery lasts 19:48
At 30mph airspeed battery lasts 13:12

Now let us fly the thing in a 10 mph tailwind at these exact same airspeeds and therefore exact same power consumption and endurance.

At 20mph airspeed the ground speed will be 30mph and after 19:48 the aircraft will land having flown 9.9 miles
At 30mph airspeed the ground speed will be 40mph and after 13:12 the aircraft will land having flown 8.8 miles

Slower in tailwind is better.

Therefore minimise time flying time upwind and maximise it downwind. Ask a pilot.

 

[adiru]

No it isnt. Look at it like this.
Mavic battery is 3830 mAh. Assume you want to land at ~%10. So we have 3447mAh usable. For simplicity we will call that 3500 mAh. Divide that by the figure of 0.10 mAh per foot specific range as determined by @Andrew F. That gives a still air practical range of 35,000' or 6.6 miles at any airspeed between 20 and 40 mph.

Now fly that distance of 6.6 miles at two speeds, 20 and 30 mph to see how long the battery lasts.

At 20mph airspeed battery lasts 19:48
At 30mph airspeed battery lasts 13:12

Now let us fly the thing in a 10 mph tailwind at these exact same airspeeds and therefore exact same power consumption and endurance.

At 20mph airspeed the ground speed will be 30mph and after 19:48 the aircraft will land having flown 9.9 miles
At 30mph airspeed the ground speed will be 40mph and after 13:12 the aircraft will land having flown 8.8 miles

Slower in tailwind is better.

Therefore minimise time flying time upwind and maximise it downwind. Ask a pilot.

Your figures are not correct at least not the first one. I recently flew a 6+ mile round trip mission on a relatively still day (3 knots wind, wind direction didn't change at altitude, I was flying crosswinds actually) and still had more than 30% battery left after shutdown. This is with me having had to waste about 1 minute and a half just coasting in the air because my Mavic took its sweet time to get the GPS lock, and Litchi crashed and I had to restart and reload the mission midair (first attempt, before it even started the mission, so Mavic was just wasting juice hovering there) before finally getting it to start the mission. My effective average cruise speed was close to 30mph, but the mission duration took nearly 17 minutes, but again, I had way more than only 10% battery left. This wouldn't have been the case had I flown at only 20mph as opposed to the max Litchi/winds allowed.

A pilot doesn't fly at 40 mph which is stall speed for any airplane. The aerodynamics in the context of the Mavic is not the same. Plus the small size because it isn't scale invariant. The Mavic shape generates lift at speed, easing the power required by the quad to stay in the air in the first place. the largest vector force component being gravity itself. Which isn't true for conventional fixed wing aircraft.

Due to the Mavic's shape, the extra lift it generates at faster speeds balances out with the extra power it needs to go that faster speed, leaving in its wake the net effect of a shortened trip, which significantly reduces total power required, thus for the same battery, increases total range.

 

[GooniesNeverDie]

He tested in still conditions/ no wind.
In any constant wind conditions, faster is still going to be better, all the way up to Mavic's top speed. At every wind speed. I've done enough long range flights to intuitively know this without seeing his charts.

On a rare day in which at different altitudes the wind changes directions in opposite ways, then fly outbound at the lower altitude layer and inbound on the higher altitude layer, in both cases always flying downwind and at maximum possible speeds. This will get you max total distance. Usually in Litchi I plot curved instead of straight waypoints, since Litchi stops/pauses at straight waypoints (wasting time and battery) and you always want to make sure the Mavic is always heading pointed directly in the direction it is actually headed at any point in time, because otherwise it really slows it down big time if the Mavic's head is pointed at an angle different from its actual track (which can happen even in no wind conditions if you did POI and had it look at something else) and it goes without saying you want to match the wind direction as to avoid crosswinds. Litchi has a bug where sometimes it doesn't want to go max speed set in the cruising setting or custom waypoints. For example you can do in the browser desktop using Litchi hub and create a mission setting everything to 33mph, but when you load it in your phone or tablet, it defaults to max of 16mph and you have to manually tell it to do 33 mph. Even then it won't do 33 mph, and once the mission starts you manually have to immediately increase speed manually to the max allowed and hold it down until it loses RC contact, because at point of signal loss whatever your speed was at that time, will be your (max) speed throughout the rest of the flight. And so its important to set the critical battery percentage to the 10%, otherwise it will be too conservative and RTH early without completing the mission even though your calculations on the numbers are good (which isn't possibly anymore in firmware higher than 400 btw) The reason I typically fly the higher alt on the way back is because it for some reason the Mavic needs to be closer in distance to require signal than the distance at which it lost signal, so it gives you more time to take manual control and go sports mode and bring it back at the maximum possible speed rather than the Litchi's 33 mph max.

It's been proven many times that "max speed" doesn't get you the most distance on a battery.

The guys on the leaderboards all talk about maintaining a consistent speed of 31 mph on a Phantom for example to attain the best life of the battery and the longest distance.

I assume the Mavic is the same, full throttle isn't the way to get the farthest on a battery.

Lastly for distance leaderboard, Litchi is cheating.

 

[adiru]

It's been proven many times that "max speed" doesn't get you the most distance on a battery.

The guys on the leaderboards all talk about maintaining a consistent speed of 31 mph on a Phantom for example to attain the best life of the battery and the longest distance.

I assume the Mavic is the same, full throttle isn't the way to get the farthest on a battery.

Lastly for distance leaderboard, Litchi is cheating.

I'm not doing Leaderboard, Yes Litchi is cheating, then again so is flying the Mavic anyway. Which is essentially already the modern day equivalent of Fly by Wire aircraft.

Try it yourself empirically, don't take my word for it. 30mph will definitely get you further total distance than 20 mph. At least on the Mavic. I never flown a Phantom so can't speak for it.

 

[Andrew F]

For the rest of the world. Is there a chart with proper metrics in Meters and KMs ?

Hahaha. I'll see what I can do.

 

[Andrew F]

I'm not doing Leaderboard, Yes Litchi is cheating, then again so is flying the Mavic anyway. Which is essentially already the modern day equivalent of Fly by Wire aircraft.

Try it yourself empirically, don't take my word for it. 30mph will definitely get you further total distance than 20 mph. At least on the Mavic. I never flown a Phantom so can't speak for it.[/QUOTE
This non-anecdotal study disagrees with you. Happy to see your data anytime.

 

[Andrew F]

He tested in still conditions/ no wind.
In any constant wind conditions, faster is still going to be better, all the way up to Mavic's top speed. At every wind speed. I've done enough long range flights to intuitively know this without seeing his charts.

On a rare day in which at different altitudes the wind changes directions in opposite ways, then fly outbound at the lower altitude layer and inbound on the higher altitude layer, in both cases always flying downwind and at maximum possible speeds. This will get you max total distance. Usually in Litchi I plot curved instead of straight waypoints, since Litchi stops/pauses at straight waypoints (wasting time and battery) and you always want to make sure the Mavic is always heading pointed directly in the direction it is actually headed at any point in time, because otherwise it really slows it down big time if the Mavic's head is pointed at an angle different from its actual track (which can happen even in no wind conditions if you did POI and had it look at something else) and it goes without saying you want to match the wind direction as to avoid crosswinds. Litchi has a bug where sometimes it doesn't want to go max speed set in the cruising setting or custom waypoints. For example you can do in the browser desktop using Litchi hub and create a mission setting everything to 33mph, but when you load it in your phone or tablet, it defaults to max of 16mph and you have to manually tell it to do 33 mph. Even then it won't do 33 mph, and once the mission starts you manually have to immediately increase speed manually to the max allowed and hold it down until it loses RC contact, because at point of signal loss whatever your speed was at that time, will be your (max) speed throughout the rest of the flight. And so its important to set the critical battery percentage to the 10%, otherwise it will be too conservative and RTH early without completing the mission even though your calculations on the numbers are good (which isn't possibly anymore in firmware higher than 400 btw) The reason I typically fly the higher alt on the way back is because it for some reason the Mavic needs to be closer in distance to require signal than the distance at which it lost signal, so it gives you more time to take manual control and go sports mode and bring it back at the maximum possible speed rather than the Litchi's 33 mph max.

We tested on both a calm day and a windy day. Those are the two lines. Statistically identical over 20 mph.

 

[Kingkong]

The data is interesting but my experience is the same as above, i get more distance at 30mph than at full speed on a phantom 4
Haven.t done enough long distance runs in the mavic

 

[jcross]

I think it is much more about momentum than drag. Once at cruise speed it should take less energy to keep it at speed, and getting g the Mavic to speed takes little more energy than hover. My thoughts anyway. Interesting science always.

 

[jcross]

I too think non prop ie body/shape lift is inconsequential on the Mavic.