# any pointers on how to figure out flight time, weight, power, etc

I am new to all this, and trying to figure out how to do rough calculations for drone configurations.

I'd like to be able to look at some motor spec sheets ... like this U15II monstor

http://store-en.tmotor.com/goods.php?id=731

and figure out with 4 motors with the prop referenced in the spec sheet, what kind of battery is needed to keep it in the air for 30 minutes.  How does that change with a 5lb payload.

Any pointers to good articles would be great.

Views: 194

### Replies to This Discussion

well , let me give you some advices

first of all , sorry for my english

you ned to sume the total max power of your motors.

for one motor and apropiated blade, the motor in function of the powe imput will produce a specific push or thrust,

you ned to maximize the aerodinamic push, try to use carbon fiber props...

(if you want a more fast reaction push-rate you ned to lower the moment if inertia of the rotor-blade so pick a lower diameter prop.... but that is for racing drones....)

well once you have the total power for example in your case: 4x(MAX POWER  (W)OF THE MOTOR AT TOP SPED)

so in your case max continuos power for onemotor is 8,54kw 4 motors is 34,2kw

Inyour case i can see that the manufacter already offers you a kit with esc+motor+propeller

you have an 180 Amperes esc, so you ned a battery that can give you 180x4=720A in his max current dischargue capacity.

Normal drone showld hover at any altitude at a 50-60 % of total throttle , in your case you have to put 33 A in each esc(motor)

to achive that. so 33x4=  132 A

nOW THE bATTERY: heare we have to do an aproximation... and we say that power P=VxI

with this you can se that the voltage of the battery has to be 50 v, and you can see, for that you will ned conect in series a pair of 7s lipo battery for example ,to get 50 v (bacause (3.7x7)x2 ) is 51)

Now the capacity of the batery normally is rated in mAh, that number is put in the battery case as "C"mAh C is a number

for example 22.000

that indicates you that that battery will las one hour discharging 22Amps...

and if the max dischargue rate of the battery is for example 50C (Max discharge current is 50x22A), than mean that in 30 minutes the battery can have a maximun current output of 2C = 2x22A=44A.... and so, more information of this kind is on internet...

s

so for your case you ned a Max peak current output of 720 A so You have to chose a Max dischargue = CxN = 720A

but in 1/2 of throttle the battery have to output a current of 132 A

that means if you want  30 minutes of flying time you ned a battery that can output a current of 132 A during 30 minutes,

and if i say well and you get me, the Capacity of the battery have to be  132/2 = 66Ah = 66.000 mAh

so you have the voltage output of the battery and capacity, and the max dischargue current its neded is 720A so if

i say well and you follow me : 720/66=11,like min. you ned a 11C Max dischargue battery rating

Normally the dischargue ratings are a lot more high, so you dont have problem with that,

Its very probable you will have to combine  2 batteries in series to feed the drone...

I recomend you to watch this video and simillar ones, and ask your suplier... dont just buy a big and fat battery, ask the seller how to use it...

but the battery its going to be very big because of its capacity, ist gona ce large cells.....

But you dont have problem because you have a lot of push with that motors, OMg you can get 36 kg of push of one motor..

so 36x4= 144 kg, are you going to ride that drone your self, it can be a taxi drone men...

i answer this very fas so maybe im wrong....

but if you are new in drones, i recomend you to start in a small less than 4 push kg drone.. you can pik a lot of tutorials out there..

Excellent info ... will take a bit to digest ... .english was fine FYI !

I don't see much discussion of using the bunch-o-battery configuration, like tesla and impossible-aerospace.  Is this because it is hard to get the discharge rate needed, weight, heat, etc or some combination of these?

https://dronedj.com/2018/09/12/impossible-aerospace-drone-tesla-eng...

21700 battery example

https://www.18650batterystore.com/ProductDetails.asp?ProductCode=Sa...

tesla battery example

https://www.ebay.com/itm/X2-Tesla-Model-3-Battery-2170-Cell-21700-b...

well im not an expertise onbatteries , but i think i can say that:

those tipe of li-ion battery cells can have dischargue ratings even more higher than li-po bateries

the energy densiti it apears to be a little more higher,, so in the same mass you have a litle bit more capacity in some models...

and i dont think there is any heat problem aswell...

maybe the enclosure makes those tipe of batteries a litle bit more wheigt....

dont know exatc to be fair.... but i can say to you that in the next months i probably going to use those tipe of batteries

And i can say to you that a prolem that a lot of people is working on is the time-charging, that all bateries have

ungawa said:

Excellent info ... will take a bit to digest ... .english was fine FYI !

I don't see much discussion of using the bunch-o-battery configuration, like tesla and impossible-aerospace.  Is this because it is hard to get the discharge rate needed, weight, heat, etc or some combination of these?

https://dronedj.com/2018/09/12/impossible-aerospace-drone-tesla-eng...

21700 battery example

https://www.18650batterystore.com/ProductDetails.asp?ProductCode=Sa...

tesla battery example

https://www.ebay.com/itm/X2-Tesla-Model-3-Battery-2170-Cell-21700-b...

I have been watching the videos you recommended ... very interesting indeed.

Is this math at all on track ...

- the U15 ii motor uses 19.9amps at 50% throttle generating 8900g of thrust (with the recommended huge prop)

- each of those samsung 21700 batteres holds 5000 mah (or 5 ah), so 10 hold 50ah

- so should be able to run the motor for 50/19.9 hours or 2.5 hours?

of course this is assuming you can finagle the voltage and drainage and be 100% efficient and drain the battery to 0 ... but applying say 50% loss to all that ... 1.25 hours?

or is this approach to estimating totally whacked

mmmm ... i think you are kind of confuse, if you put 2 batteries in series, you double the voltage but the capaciti stil the same,

only when you put 2 batteries (cells) in parralel the output capaciti is doubles..

chek this video

ungawa said:

I have been watching the videos you recommended ... very interesting indeed.

Is this math at all on track ...

- the U15 ii motor uses 19.9amps at 50% throttle generating 8900g of thrust (with the recommended huge prop)

- each of those samsung 21700 batteres holds 5000 mah (or 5 ah), so 10 hold 50ah

- so should be able to run the motor for 50/19.9 hours or 2.5 hours?

of course this is assuming you can finagle the voltage and drainage and be 100% efficient and drain the battery to 0 ... but applying say 50% loss to all that ... 1.25 hours?

or is this approach to estimating totally whacked

Also ... you mentioned ... “so 36x4= 144 kg, are you going to ride that drone your self”

I am actually most interested in flight time ... and trying to figure out what it takes (or if possible even) to lift 5 pounds for 6 hours !!!!

Excuse me, i went to sleep.

I mean, Yea why not.

its gone cost you some dollars but, yea it showld work more or less.

If you test it , please show video :)

ungawa said:

Also ... you mentioned ... “so 36x4= 144 kg, are you going to ride that drone your self”

I am actually most interested in flight time ... and trying to figure out what it takes (or if possible even) to lift 5 pounds for 6 hours !!!!

Use Ecalc. Does exactly what you're asking for and much more.

o wow, fantastic page, nevertheless i also like to do it my self ,

Checkers said:

Use Ecalc. Does exactly what you're asking for and much more.

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