Most battery efficient speed to cover a distance

[cpper]

I have a Mini 2 drone and am wondering what is the most battery efficient speed to fly:
- horizontally from point A to point B
- vertically from altitude A to altitude B

,regardless of the time it takes to cover that distance, and in the same weather conditions.

CINE mode at max speed of 6m/s flies 300m in 50 seconds, and consumes x1% battery
NORMAL mode at max speed of 10m/s flies 300m in 30 seconds, and consumes x2% battery
SPORT mode at max speed of 16m/s flies 300m in 19 seconds, and consumes x3% battery

How different are the values of x1 ,x2 and x3, and what is a short explanation of these differences ?

Thanks for your time

 

[Tomk_]

Based upon the criteria and parameters presented... all you care about is distance and battery consumption.

In cine mode you are consuming .003333% of your battery for every meter flown.
In Normal mode you are consuming .006667% of your battery for every meter flown.
In Sports mode you are consuming .01% of your battery for every meter flown.

If you cared about time, then time versus consumption would be:
Cine mode = .02% consumption per second
Normal mode = .0667% consumption per second
Sports mode = .15789% consumption per second.

I must say that I question the consumption rates. I find it unlikely that each of the data points would be exactly 1% apart.

 

[cpper]

Thanks Tom for the explanation. May I ask where do you got the data from (consumption / meter in each mode) ?

 

[Tomk_]

1%/300m = .003333%/m
2%/300m = .0066667%/m

 

[cpper]

Oh, I see what's going on, and just now I understood the final line in your first post. My fault.
With x1, x2, and x3 I was referring to 3 unknown variables. I should have said x, y and z instead. I'm not aware of any consumption rates, this is what I'm trying to find out. English is not my first language and I expressed myself wrong.

So basically I'm trying to find out the following: At what speed (or, in which mode) do I have to fly from point A to point B in order to consume the least amount of battery ?

 

[StantonZ]

So basically I'm trying to find out the following: At what speed (or, in which mode) do I have to fly from point A to point B in order to consume the least amount of battery ?

Based on this question, I believe NORMAL mode (max speed) is the most "battery efficient" way to cover a given distance. In fact, I finally had a flight (last weekend) where I hit the "RTH low battery" (or max distance) point...before I lost radio connection. I ended up returning with ~25% battery (probably because I was returning with the wind), but the entire flight was done in NORMAL mode.

 

[spudster]

May guess it is what DJI has in their specs for maximum flight time. IMO it seems they would want to use the most efficient setting so they can claim the highest flight time possible. That spec is:

31 mins (measured while flying at 4.7 m/s in windless conditions)

 

[Grazuncle]

I'm throwing this into the mix. Perhaps something else has the same thought.. but I seem to remember that resistance ( the atmosphere in this example) and speed increase is not a linear plot. So increase in power/energy brings diminishing returns. It may be predictable ( in sure DJI know exactly the efficiencies in different scenarios) but I don't think linear.

 

[cpper]

@StantonZ Thanks for the advice. So, max speed in Normal mode.
@spudster That's interesting to know, but that setup aims to achieve the longest flight time. I'm looking for greatest distance instead.
@Grazuncle Exactly, I'd love to see that curve, and to know the explanation behind it.

 

[JackL]

I have a MA2 and Normal is by far the most efficient for me. I've pulled off some unbelievably long flights in N with favorable wind shear. Sport mode is way more fun but cuts my flight time in half in some cases.

 

[Tomk_]

Here is some older data that you might find helpful.

Drone Flight Stats - Part 1 | Airdata UAV Drone Blog

MPB: Minutes Per Battery Like MPG (Liters/100Km) For Drones How efficient your drone flights? We took look our over 2,000,000... Read more!

airdata.com

 

[Tomk_]

I don't believe that the mode you are in effects efficiency of the drone. It's not like you are changing gears or anything. Speed is speed. Different modes just give you reduced throttle output.

Looking at the Airdata Data for the Mavic Pro...
At 10 mph you can go approx 4.5 miles on a pack.
At 20 mph you can go approx 7 miles on a pack.
At 30 mph you can go approx 7.5 miles on a pack.
At 40 mph you can go approx 8 miles on a pack.

So, at least on the Mavic Pro, it looks like the faster you go, the more ground you can cover on a power pack.

 

[JackL]

I don't believe that the mode you are in effects efficiency of the drone. It's not like you are changing gears or anything. Speed is speed. Different modes just give you reduced throttle output.

Personally I believe the tilt of the drone in the various modes combined with the wind is responsible for the varying efficiency. Somehow the tilt N gives is most efficient for the sort of long distance, into the wind flying I do. If I have a huge tailwind and kick it in S I can use almost no battery and maintain full speed returning since it seems to act like a sail. I once managed a 34 minute flight with 20% left using this technique.

 

[DougMcC]

All fixed wing aircraft have a single best range (best glide) speed. Any speed slower or faster in level flight will consume more fuel per mile. Quad copters may be different. Induced drag is an exponential function of speed I believe for anything flying through our atmosphere.

 

[StantonZ]

So, at least on the Mavic Pro, it looks like the faster you go, the more ground you can cover on a power pack.

This extrapolation just doesn't hold...for any "moveable" object with a finite power source (like a battery). There is a peak efficiency that rapidly deteriorates with speed. I don't know what that curve is for our drones, but here is one for my Leaf (an EV); I would expect at least the shape of the curve to be similar.

 

[Drbobk]

This extrapolation just doesn't hold...for any "moveable" object with a finite power source (like a battery). There is a peak efficiency that rapidly deteriorates with speed. I don't know what that curve is for our drones, but here is one for my Leaf (an EV); I would expect at least the shape of the curve to be similar.

I agree, but I’d add this. I think the difference between an automobile and a drone is that the auto’s cross sectional profile against the wind doesn’t change with speed, but the drone’s does as it ”leans” forward in order to change its thrust from up only to both up and forward. I expect that that increases the cross section and increases drag even more than just the speed does. So it’s more complicated than simply “wind resistance increases as the square of the speed.”

 

[wardtom084]

Basically the faster you go the more energy it takes. Just physics.

 

[Drbobk]

Basically the faster you go the more energy it takes. Just physics.

This misses the point. If it took exactly twice the energy to go twice as fast, then both would be equally efficient. The question is whether the endurance goes down linearly with increasing speed or not.

 

[BudWalker]

It was pretty well established that the Phantom 3 series had maximum distance at maximum speed. It's been so long that the posts supporting this are no longer available. I believe this was also shown to be true of the Mavic Pro and the Phantom 4. And, I suspect this true for the other DJI platforms since and after the Phantom 3.

 

[BudWalker]

This extrapolation just doesn't hold...for any "moveable" object with a finite power source (like a battery). There is a peak efficiency that rapidly deteriorates with speed. I don't know what that curve is for our drones, but here is one for my Leaf (an EV); I would expect at least the shape of the curve to be similar.

Probably the same shape. But, at least for the P3 and MP, the scale is different. I.e. the P3 or MP max speed is less or equal to the peak efficiency.