What calculation did you use?
When I put that through eCalc with the values you gave and assumed everything you didn’t mention, I get a hover flight time of 17 minutes. What TOW did your drone have during the test flight you did?
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The Mtow is 3.6kg sir .
what battery are you using? is it flat cell lipo or round li-ion cells?
going by the Tmotor spec sheet it should only be using around 4.1A per motor for 900g per corner giving 3.6kg total at 16.4A but your using around 5.3A per motor using around 21A total.
The only thing i can see is some imbalance in your motor output. If it’s round arms, then I would guess one is twisted a little.
Tattu 16000mah Lipo battery sir, Level checked all the motors sir , but still consuming higher amps
Is 3.6 kg the take-off weight for that test flight or is it the maximum take-off weight the drone will ever have? Just to clarify confusion, you wrote in the original post that you have an MTOW of 6 kg.
MTOW ≠ TOW
With a TOW of 3.6kg eCalc agrees with your observation of 36 minutes.
What calculation did you use originally?
we used to calculate as Amps consumption during flight/MAH of battery and the 60/(Amps consumption during flight/MAH of battery) ie 16.4/16=1.025 and then 60/1.025=58mins
I think a major difference with reality is that you cannot empty a LiPo completely. It would kill your battery if you emptied all 16Ah. Draining 16Ah of your battery will lower the voltage to 0V (dead). Another major difference with reality is as you lower the voltage of your battery during flight, you consume more amps to turn the rotor at the same RPM.
From experience, using test data is never 100% accurate. The arms holding the motors block airflow from the rotors. Airflow being sucked in your props can interact with the airframe. Also, test data doesn’t account for any other electrical component (but that usually makes only a minor difference though).
eCalc probably has a better battery model than yours, making it more accurate than your back-of-the-envelope calculations.
@Oli1 has another point. If your drone is untuned, and keeps making minor oscillations, that will drain your battery faster. Heck, if you use BLHeli ESCs, there are parameters in the ESCs firmware you can play with to make your ESC/motor/prop combo more efficient. It’s not impossible that your default ESC params are badly set for the motor/propeller combo you’re using.
You also have 3 motors at a higher throttle, and 1 motor at a lower throttle. Current consumption is exponential with thrust. If your drone is unbalanced, the total power consumption is greater than if your drone is properly balanced (center of mass at the geometric center between your 4 motors).
But, no matter what you do you won’t get anywhere near 58 minutes.
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@bobzwik @dkemxr @Janno @geofrancis @amilcarlucas @Oli1 thank you all for your time and suggestions,i will try with different motor and frame and will update you . And i want to make a drone with 1hour endurance with Tow of 5kg including battery, please give me suggestion for selecting perfect propulsion system and other components
Lighter frame and Lithium Ion batteries instead of LiPo batteries. They hold more capacity per kilogram, but their maximum output current is less. They are also more expensive.
Otherwise, larger props = better efficiency. The motor tables from motor manufacturers are good enough to compare motors, just not 100% accurate to estimate current draw. If you don’t need a huge maximum T/W ratio, choose propellers that aim for efficiency instead of max thrust.
And then to squeeze the endurance to the max, properly balance your quad and properly tune it.
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To get over 1 hour you need to be ruthless with weigh saving, you will need to get the lightest components you can get,
starting with the battery. your current battery is almost 2kg. you can drop that down to around 1.3kg with a 6s3p pack using 5000mah li-ion 21700 cells.
for my light builds
use the lightest flight controller, it doesnt sound like much an orange cube is almost 80g where you can get a matek h743 thats 9g.
Lightest ESC 4 in 1s are usually lighter than individual ESC, and you dont need a big one, a 4x20a would be enough.
lightest GPS with a thin carbon mount, the folding mounts are heavy.
Lightest receiver that could do mavlink telemetry and RC, big receivers with big telemetry radios add weight.
lightest VTX and camera
titanium nuts and bolts.
you probably wont need to go to that extent but you should weigh every component and see where you can save weight because it all adds up.
Something else just occurred to me, what altitude are you at? Are you up in the mountians? Because the thinner air will cause it to use a lot more power than at sea level.
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Buy a subscription to eCalc and get to work. You will find it difficult to achieve your goal.
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I think his best idea would be to go to ecalc and set his motors and a 6s 15ah battery then work out how light it needs to be to fly for an hour by changing the weight on ecalc. once he gets the weight he can then start weighing parts to work out where the weight can come off to get down to where it can fly for an hour.
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I had a 14” quad that would “fly” (hover) for 45 minutes but that’s all it would do as it carried nothing. It flew some impressively long missions to nowhere and back…
Or the YouTuber who’s craft hovered next to a clock for 1hr. Like watching paint dry.
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that’s all mine to do these days, I like building and designing them more than actually flying.
That was essentially how I tested my endurance quads, I was so happy when I got optical flow working so I didnt need to manually fly it.
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I am with you on that!
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I have a quad with the same motors and props, and I use a Tattu 6S 8Ahr pack. Despite having some unusual constraints with the frame design, without any useful payload it’s around 2.5 kg, and will hover or cruise efficiently for close to 40 minutes, using about 80% of the battery’s rated capacity.
Power to cruise at 10 m/s is about the same as hover due to translational lift.
I’ve flown at weights up to about 3.6 kg, and safe endurance drops to around 15 to 18 minutes. I think 900 g per motor is above what T-motor recommends for the MN4006, but for enduance builds I’ve found that I do well to push them a little harder.
All the advice regarding weight is spot on - for hover and slow cruise flight. However, if your goal is to achieve some cruise speed capability, steeper pitch props and a heavier disk loading are critical, as is a streamlined body. Super light copters with flat props can never fly fast efficiently. I’m not sure an hour is achievable for a quad like that though.
A guy named renatoa came up with some math for calculating flight times. I use it for all of my drones.
Here is his post on RCGroups:
" For any platform of any size and weight, the flight time is the result of:
time = whkg / (1000*R / eff_gw) * 60, where
whkg = battery energy density, in Watt hour / kg, ranging from about 150 for the high C packs to 270 for LiIons. 10C Multistars are 185.
R = ratio between AUW and battery weight
eff_gw = motor/prop efficiency, grams per Watt, taken from mfr data.
Be aware to get from table the efficiency for the intended thrust, and for 50% throttle !
Efficiency greatly depends on load, so don’t use efficiency stated for 1kg, to compute flight time of 2-3 lg platform !
Also, don’t use values for more than 60% throttle, the platform will be unstable, no more room for motors to do their control job…
As I wrote, this formula works for ANY size platform and energy source, lets do the math for some particular cases:
Case I Ph2
battery wh/kg = 5.2(Ah)11.1V/0.37(kg) = 156wh/kg
R ratio between AUW and battery = 1250/370 = 3.4
propulsion efficiency = 11g/W
time = 156 / (10003.4 / 11) * 60 = 30 min
Case 2 the 129 min record
battery wh/kg = 266Wh/kg - typical LiIon energy density
R ratio between AUW and battery = 3.4/2 = 1.7
propulsion efficiency = 14.1g/W
time = 266 / (1000*1.7 / 14.1) * 60 = 132 min
And finally, my 30 min case
battery wh/kg = 165, I use a Zippy Compact, having a bit more energy than the average LiPo
R ratio between AUW and battery = 0.75/0.195 = 3.8
propulsion efficiency = 11g/W - using Phantom 2 clone
time = 165 / (1000*3.8 / 11) * 60 = 28 min
As you can see from the above, reasonable precision of all estimations, proving this formula is valid for any configuration, so now you have a tool that should tell you what is wrong in your setup, and where to work to improve flight time.
The biggest unknown for most users is the propulsion efficiency, for this reason I think is mandatory to not buy stuff without manufacturer precise specification of this parameter."
I have attached a spread sheet that will do the math for you.
Calc.zip (9.2 KB)
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