Help!

[DavidtheDJ]

Hello there,

I am here to ask for some help. I have been putting my together my own quad for sometime but as I have been adding more and more to it, the heavier is has gotten. I'm trying to get in the air after I put new motors and ESCs that I thought would work. I now have TURNIGY Plush 40amp ESCs powering Turnigy Multistar 3525-750Kv 14Pole motors but with my setup I am using 3/4 of throttle to get it to rise. I am also worried that the motors don't have the power on demand that it needs to make the adjustments it needs to level itself. Would 50amp ECSs(HK Blueseries) be fine with the motors I have bought?

Here is what is on the muiti-rotor when fully loaded.(Bought all parts from hobbyking)

TURNIGY Plush 40amp
Turnigy Multistar 3525-750Kv 14Pole Multi-Rotor Outrunner
15x4E Carbon Fiber Propellers
ZIPPY Flightmax 5000mAh 3S1P 20C
ImmersionRC EzOSD FPV on Screen Display
FatShark Teleporter V3 RTF FPV
Headset System w/Camera and 5.8G TX
Quanum Q-2D Brushless
Gopro hero 4 black
Hobbyking X525 V3 Glass Fiber Quadcopter Frame 600mm
Hobbyking KK2.1HC Multi-Rotor Hard Case Flight Control Board
some light weight parts

Also was going to upgrade my control board to a DJI Naza-M Lite with GPS. Would it still be okay?

Thank you for responding! Yes I am new.

 

[ZoomNBoom]

Somewhat weird setup there. FC and frame wouldnt exactly be my first choice, 3S battery probably not the best idea either for such a heavy setup either, but anyway. Those motors are rated for 900+W and should provide ~1.2Kg thrust each with those props at 3S. How heavy is your copter?

Then there is the battery. Its a 20C x 5A= 100A. In theory. In reality dont expect more than half that sustained.
Yet your esc's are sized for 4x40 = 160A. And while I dont have any data on your specific motor, each would seem to pull on the order of 30A WOT, so ~120A total. Your battery wont be able to provide that, and will sag badly. Id seriously consider going to 4S with smaller props.

There may be other issues too, but lets start by hearing the AUW.

 

[nilsen]

I would say you should move to a 4S battery, 3S on those motors and ESC's isn't ideal for that weight quad.

 

[Cyberdactyl]

I have to agree with zoom. That is a peculiar build. Brute motors with what sounds like somewhat large props for the size of the motors. And that is a huge battery as well. That build is really asking for 4S or more, but with maybe 1245 or 14" props.

If all you want to do is ultimately lift a GoPro, gimbal, FPV cam and a Vtx, you could drop the size of the motor's height, but keep the KV. What I'm suggesting is move to something like the 3508 700KV with 1245's. That would provide plenty of lift with half the weight and a lot less power draw. That will cut the mass by >400g right there. That is still overkill for what you listed to lift, but just less so.

Also no real need for 40A ESCs in either case. High rated (>30A) ESCs are overkill for 90% of MR flyers. Unless you're going to be cranking wide open throttle for extended periods or trying to lift large loads, there's really no need. However, if you stick with 5000mAh, a 30A might be justified. The motors I linked lifting a ~1800g quad does not need more than 30A, and probably would work great with 20A, most especially if you allow them some air across the heat sink plate.

And yea, switching to DJI board is ok. Just be aware going from a KK2 to a DJI with GPS is a jump in complexity.

 

[DavidtheDJ]

Somewhat weird setup there. FC and frame wouldnt exactly be my first choice, 3S battery probably not the best idea either for such a heavy setup either, but anyway. Those motors are rated for 900+W and should provide ~1.2Kg thrust each with those props at 3S. How heavy is your copter?

Then there is the battery. Its a 20C x 5A= 100A. In theory. In reality dont expect more than half that sustained.
Yet your esc's are sized for 4x40 = 160A. And while I dont have any data on your specific motor, each would seem to pull on the order of 30A WOT, so ~120A total. Your battery wont be able to provide that, and will sag badly. Id seriously consider going to 4S with smaller props.

There may be other issues too, but lets start by hearing the AUW.

I agree that the FC and the frame are now not the best for what I have and that the motors where bigger then what I expeted. I think I will go out and buy a 4cell battery and try it out. I have some smaller props that I used on the way so I can try those out when my other stuff comes.(Moving right now) Do you guys think that I should go for a mid to high c rating?

I don't have a scale to check the weight of the multirotor but I will get that asap.

 

[DavidtheDJ]

The weight of the fully loaded copter is about 5pounds or about 2.2 kg.

 

[FlagstaffMike]

The S rating is not going to do anything about the amperage output of the battery so yes it looks like you need to up the C rating of the battery as well.

That being said you have a 5ah battery so based on Zoom's math you would only have to go up to 25c to provide the output, though as mentioned you should overshoot the c rating you think you need to be safe.

 

[Cyberdactyl]

Opps, sorry, I thought you were looking to buy, not that you already purchased. My mistake, you did say 'bought'.

Anyway, those huge motors need at least 4S, and probably 5S would be better. You need to utilize that higher voltage to push up the rpm to lift that 233g per motor. And the 625g 3S 5000 isn't helping.

 

[ZoomNBoom]

The weight of the fully loaded copter is about 5pounds or about 2.2 kg.

Hardly a featherweight, but it should be able to lift that with little problem I would think. You sure you calibrated the ESCs and everything properly? Do you have any sort of battery voltage monitoring/telemetry? Would love to find out how badly the voltage sags under load.

The S rating is not going to do anything about the amperage output of the battery .

At higher voltage, you draw less amps to get the same power (watts). So going to 4S (on smaller props, which you will need anyway to prevent burning out the motors) will help also to reduce the amperage.

 

[DavidtheDJ]

Hardly a featherweight, but it should be able to lift that with little problem I would think. You sure you calibrated the ESCs and everything properly? Do you have any sort of battery voltage monitoring/telemetry? Would love to find out how badly the voltage sags under load.

The ESCs and FC gyros are both calibrated. I have the OSD that tells me battery info as well as a battery voltage meter. On my next flight I can post the readouts.

 

[Cyberdactyl]

I think it's simply a heavy quad with heavy, low KV motors trying to spin quite large props with 3S. My guess is hover takes about 60% throttle.