I was pondering the question of fuel efficiency in a quad copter. Back in the 1970’s the federal government introduced the 55mph speed limit arguing that efficiency drops of sharply above that. However quadcopters are quite different from cars and while running the motors at maximum power will certainly discharge the battery faster I have this hunch that one would achieve the maximum horizontal distance on a battery by flying at maximum speed. Does anyone have any insight into this question or even just baseless opinions?

  

Testing has shown that the max distance per battery is reached at a speed a little below the max P-GPS speed with obstacle avoidance disabled - about 14 metres/sec.
Because the difference between the max economy speed and full speed is small and wind makes every flight different, you may as well use full P-GPS speed and you'll be close to max economy.
Using Sport mode kicks you up into a different battery draining zone and you cover less distance with the battery.

Just a comment - but the 55mph limit imposed by US Govt all those years ago was shown to NOT be best fuel efficiency .. that in fact it was over 60mph should have been used. (I was a Senior Manager - North Russia and Baltics - of the Company that worked with EPA   and it was well known inside the Co. about this error).

As to battery / speed / distance ... the only way to check this in reality is Telemetry or Wattmeter as used by other RC ... anywhere near full throttle is noted as less efficient in all LiPo models I have and I can only assume that the DJI will be same. I have light floaty, heavy high speed, EDF, Prop, boats, cars ... and all average out at about 70% throttle is most efficient.

Why ? It is not only the amp draw vs mAh capacity. It is also the temperature factor of the cells. As the amp draw increases - the temperature rises and you actually reduce the amount of mAh you can draw on before LVC cuts in ... (Low Voltage Cutoff). This is a safety mechanism in ESC's to try prevent cell damage from too low a voltage level. As temperature increases - Internal Resistance increases causing greater voltage drop ...
It is easily seen by flying a LiPo till it refuses to fly anymore .. LVC cuts in basically. If you measure the voltage at that point and then let cells cool - you will find that voltage has increased once cooled. In fact the cells would likely fly again .. albeit only for a few seconds.

So if you want maximum flight - do not go full throttle. ease back to 70 - 80% is my suggestion.

I know when I used to push my Standard out to 4 - 5kms range - I always was careful to not use full ...

You also have to remember you are flying a 'brick'. Unlike a fixed wing machine - there is no residual glide factor from forward speed. Higher speed with FW can lead to a longer glide till landing. With a Drone - forget it ... props stop - it drops like a stone. Speed has given you nothing.

Nigel

https://phantompilots.com/thread ... ciency-tests.90851/