Battery Efficiency : Sport Mode vs P (GPS Mode)

[FlyGuy8675309]

Anyone have any data on this? I'm wondering because I've seen people but quads in sport mode to get home quickly when the battery is low. To me it's like flooring it when you are on E to get to the gas station quicker -- you are using the fuel a lot more quickly and less efficiently. Same with the Mavic?

 

[Mako79]

An unlocked Mavic on supersports is much more efficient with battery when descending. I guess its like leaving your car in neutral on a downhill.

I do agree though, i wish there was an ECO mode on the mavic where it could figure out the optimum speed vs battery consumption.

 

[FlyGuy8675309]

I do agree though, i wish there was an ECO mode on the mavic where it could figure out the optimum speed vs battery consumption.

I'm thinking the GPS / P mode is pretty close to that ideal. I guess it's time to do some experiments.

 

[Lapeer20m]

Search ....there are threads dedicated to proving this out.

Basically, the faster you fly the more miles per battery mavic will travel.

Conversely, Flying slower will get you more minutes per battery.

 

[dwallersv]

I'm thinking the GPS / P mode is pretty close to that ideal. I guess it's time to do some experiments.

Think more carefully about what your saying here... GPS/P mode is not a speed.

Are you referring to the maximum speed in P mode? That makes sense, insofar as being internally logically consistent. What you were saying before was like, "what is the color of sweet?"

Okay, that picked apart , I don't see any reason to assume max speed in P mode is necessarily the most efficient speed in terms of battery time duration. However, this is the wrong metric to pay attention to -- you're interested in best distance efficiency -- i.e. most feet/mAh of remaining charge.

You can make the battery last longer by flying slower, but contrary to intuition this might not get you home. The degenerate example that proves the point is flying at speed 0 -- you'll probably get the most time out of your battery hovering after you reach some destination, but you also will end up going down a long way from home.

Anyway, without going deeper into this rather complicated physics/math problem, people have done controlled experiments with the Mavic to measure this. Greatest distance one gets on a battery seems to be at around 32-33 mph.

 

[Bernie707]

Think more carefully about what your saying here... GPS/P mode is not a speed.

Are you referring to the maximum speed in P mode? That makes sense, insofar as being internally logically consistent. What you were saying before was like, "what is the color of sweet?"

Okay, that picked apart , I don't see any reason to assume max speed in P mode is necessarily the most efficient speed in terms of battery time duration. However, this is the wrong metric to pay attention to -- you're interested in best distance efficiency -- i.e. most feet/mAh of remaining charge.

You can make the battery last longer by flying slower, but contrary to intuition this might not get you home. The degenerate example that proves the point is flying at speed 0 -- you'll probably get the most time out of your battery hovering after you reach some destination, but you also will end up going down a long way from home.

Anyway, without going deeper into this rather complicated physics/math problem, people have done controlled experiments with the Mavic to measure this. Greatest distance one gets on a battery seems to be at around 32-33 mph.

 

[Bernie707]

What is the most efficient speed in terms of lowest battery discharge is an interesting question. I only know that hovering will supposedly discharge a battery faster than forward flight.

 

[Stunnajd112]

In terms of battery efficiency, DJI says 27 mins with 0 wind at 15.5 mph or 25 kph.

 

[Mako79]

The biggest lost in battery is the restrictive descent speed. Its the equivalent of running down a steep hill, where you use more energy in slowing yourself down. DJI should look at increasing this speed as the Mavic is not prone to VRS as much as the heavier sibblings

There has been reports of Mavics descending from 2km heights using only 2% battery.

 

[FlyGuy8675309]

Think more carefully about what your saying here... GPS/P mode is not a speed.

Are you referring to the maximum speed in P mode?
.

Yes thank you - I could have explained that better. I was thinking about this because a car radio show host was explaining how fuel efficiency goes down fast past 60mph in a automobile. -- was wondering if the same principle was at work. Thanks for all the feedback - I learn a lot here!

 

[EsiMavic]

A question about Sport mode & battery efficiency

 

[Porto]

Greatest distance one gets on a battery seems to be at around 32-33 mph.

I agree with you here. With calm wind, GPS mode with OA off, and no change in the normal flight parameter, the Mavic will fly at about 50kph (31mph). I believe it is the speed that can get us the longest distance.

What I am not so sure however, is when we are going back to home point and we are fighting headwind. If the Mavic barely moves forward in normal mode, it's obvious we have to switch to Sports Mode. But what if the Mavic can still fly at about 33kph (20 mph) in normal mode and about 40kph (25mph) in Sports Mode AND it is still very far away from home? I think normal mode is more efficient, but I could be wrong.

In my thread titled "Don't be deceived by calm wind", I was in that situation. I did manage to bring it home using normal mode (OA off). But maybe I should have done it under Sports Mode?

 

[dwallersv]

What is the most efficient speed in terms of lowest battery discharge is an interesting question. I only know that hovering will supposedly discharge a battery faster than forward flight.

not true.

 

[dwallersv]

I agree with you here. With calm wind, GPS mode with OA off, and no change in the normal flight parameter, the Mavic will fly at about 50kph (31mph). I believe it is the speed that can get us the longest distance.

What I am not so sure however, is when we are going back to home point and we are fighting headwind. If the Mavic barely moves forward in normal mode, it's obvious we have to switch to Sports Mode. But what if the Mavic can still fly at about 33kph (20 mph) in normal mode and about 40kph (25mph) in Sports Mode AND it is still very far away from home? I think normal mode is more efficient, but I could be wrong.

In my thread titled "Don't be deceived by calm wind", I was in that situation. I did manage to bring it home using normal mode (OA off). But maybe I should have done it under Sports Mode?

in terms of performance efficiency, wind does not exist for aircraft. Think about it.

 

[Ron_Dog]

in terms of performance efficiency, wind does not exist for aircraft. Think about it.

WHAT?

 

[vimagreg]

WHAT?

x2

 

[FlyGuy8675309]

in terms of performance efficiency, wind does not exist for aircraft. Think about it.

I think YOU need to think about it. LOL.

 

[dwallersv]

An aircraft flies relative to the air, not the ground. If it is most efficient in terms of distance traveled / mAh consumed, then this will be relative to the airmass it's flying in, not the ground below.

Exactly the same for a boat relative to water. Or a car relative to the ground. Each of these is a "frame of reference".

Just because what you're interested in is the ground doesn't change the physics of the situation. This is an excellent example of "Galilean Relativity"... look it up. These are freshman physics problems.

The entire system amounts to a reference frame translation, with a constant speed difference between the two reference frames that is the wind speed. As such, the entire system is linear, so it doesn't matter that you are in a different reference frame from the aircraft, it is still flying at it's peak translational efficiency in your reference frame, just at a slower (or faster) speed relative to you.

Now, the one thing that does mess this up is the Flight Controller sitting in the middle, using GPS data to manage heading and speed. So we can't actually set the ESCs at the optimum, most efficient operation via stick deflection, because the FC will try and maintain a constant ground speed based on demand from the stick position. So, when there's wind, we don't have the proper feedback (airspeed) to truly maintain a constant peak efficiency in flight.

So, in the end the true answer to the original question is, "can't control it", so there is no "optimum speed". The "speed" that we use to run test series and attempt to determine efficiency is an exceedingly poor metric, as it is really airspeed that we need to measure against. Probably the closest we could get would be to do a series of tests maintaining different prop RPM, since we have that feedback on the Mavic controller. Of the data we have available, RPM is the closest to a (flawed) proxy for airspeed.

 

[dwallersv]

Anyone here with a ticket that's flown VFR with just basic instruments knows exactly what i'm talking about. Engine efficiency is @ RPM and airspeed, has nothing to do with ground speed -- for the long, egg-head explanation I gave above

 

[Porto]

in terms of performance efficiency, wind does not exist for aircraft. Think about it.

I surprised myself that I actually get what you mean

Reading your explanations on the following posts confirmed that indeed I get it. I am planning to do some tests this weekend: doing Sports Mode, keeping the RPM at around 60% (is it the most efficient for the motors?), and compare the ground speed with what I get with P mode OA off.