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Newbie trying to troubleshoot electronics... (solved)

John_W

John_W

New member
Trying to put together some electronics for my second scratch built fixed wing, a smaller and lighter variant than my first 1500mm wingspan one.
So maybe someone with more understanding of this RC black magic have enough experience to guess where the problem is?

Since I hand picked the parts from aliexpress I thought I should make sure it works together but what happens is the current draw and motor RPM (audibly) maxes out at 6.5A which is right around half-throttle on the stick, going up in throttle after that does not increase current draw from battery and the motor does not change in sound at all..

From my very limited understanding of how this stuff work, the first failure mode SHOULD be either the ESC burning up or motor windings melt? But I'm only getting soft failure of something throttling the current flow, and I have no clue where the bottleneck might be.

Forgive my paint-schematic but hopefully it's clear enough to see how I went about measuring
schematic.jpg


Parts used:
RS2205 _ 2300KV 2-4S rated motor (external link, aliexpress)
Cheap variant 20A rated BL-Heli ESC (no bec) (external link, aliexpress)
Turnigy 8-26V in SBEC (external link, amazon)
Vapex 3S 2200 mAh Li-Po (external link, hobbylinna)
FlySky ia10B rx
FlySky FS-i6S tx

Any ideas, tips or feedback in general are welcome! :)
 
CarolineTyler

CarolineTyler

Legendary member
Those connections look fine to me. I am assuming your ESC does not have an internal BEC.
Have you calibrated your BEC so that it responds to the full range of throttle?
Video on doing this...
 
kdobson83

kdobson83

Well-known member
CarolineTyler said:
Those connections look fine to me. I am assuming your ESC does not have an internal BEC.
Have you calibrated your BEC so that it responds to the full range of throttle?
Video on doing this...
Click to expand...
I second this. I've ran into this exact problem before. Simple throttle stick end point calibration fixed it right up.
 
John_W

John_W

New member
That is amazing I had no idea you have to calibrate ESC's... I followed the steps and now I have a full gradient from 0% to 100% throttle, however the 100% is still 6.5A current draw, is it possible that is the max this motor will draw with this prop? Do I need to get a more aggressive pitch prop to make use of the heavy 3S power system? Or could there still be an electronical problem somewhere?

In either case this was really useful information thanks a bunch! :)

Edit: sorry should have added in the original, the Motor manufacturer recommends "HQ 5045 BN" prop, I picked out some 5045 4-bladed that I'm running on so I don't think the prop should be undersized?
 
CarolineTyler

CarolineTyler

Legendary member
So that means you are pulling 85 watts if the battery is full - I would expect the motor to be capable of around 130 watts. 2300kv 2205 motor - I would on a quad put a 5045 3 blade prop on it. Maybe a 6045 2 blade.
If there is no prop on the motor you will not pull high watts as there's nothing for the energy to go into. Equally the watts measured when testing on the bench will be slightly more than on the flying model as the forward movement of the air 'unloads' the prop a bit.
 
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John_W

John_W

New member
I guess I will try on one of my bigger 1045s, way oversized but at least the current draw should go up, if it doesn't means the problem is in the ESC probably? Good thing I have spare motors and ESC if they burn up but safety-squints will definitely be engaged.
 
CarolineTyler

CarolineTyler

Legendary member
John_W said:
I guess I will try on one of my bigger 1045s, way oversized but at least the current draw should go up, if it doesn't means the problem is in the ESC probably? Good thing I have spare motors and ESC if they burn up but safety-squints will definitely be engaged.
Click to expand...
1045 is way to big for a 2205 2300- you will burn up the motor or maybe the ESC trying to drive it!
 
John_W

John_W

New member
Ok Update the prop is simply undersized I concluded after going up to 10 Amps at 75% throttle with a 1045 2blade on, Can't go higher while measuring or I'll blow the fuse on my multimeter, so I think we can conclude this matter solved!

Thanks so much for your help! I'll probably try to make this fly on a twin engine setups with the undersized props, until I get my hands on some bigger or more aggressive pitch ones.
 
John_W

John_W

New member
So 10 A is pushing the limits, thanks I will heed that warning and order some sample props and see which ones will land me on about 8A full throttle.

That meter looks useful will have to order one like that. Thanks again!

Is it possible to somehow test the absolute limits on my motor, or just burn one and go down a notch from there? ;)

I'm also surprised the manufacturer recommends the 5045 prop as it clearly is underperforming on this motor...
 
FDS

FDS

Elite member
If your motor gets too hot to touch after a burst of full throttle you have too much prop. I like 6040 APC style props on smaller motors.
 
CarolineTyler

CarolineTyler

Legendary member
John_W said:
So 10 A is pushing the limits, thanks I will heed that warning and order some sample props and see which ones will land me on about 8A full throttle.

That meter looks useful will have to order one like that. Thanks again!

Is it possible to somehow test the absolute limits on my motor, or just burn one and go down a notch from there? ;)

I'm also surprised the manufacturer recommends the 5045 prop as it clearly is underperforming on this motor...
Click to expand...
When looking for motors it's useful to see a chart showing expected pull/watts/amps etc. for a range of props - saves the pain of destroying motors :)
Banggood are usually pretty good about putting such info in their descriptions, more labeled makeres like EMAX give lots of info. If there's no table and no peak watts for a motor listed then it's down to guesswork and touching hot motors!! ;)
 
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John_W

John_W

New member
Thanks, yes the 1045 is definitely oversized, after running it on 9A for about 15 seconds the base of the motor that the windings are attached to was uncomfortably hot, not enough to burn skin though.

Running the 5045 4blades on it on full throttle 6.5A I cannot measure above 30°C (86 F) anywhere on the motor even after continuous run on max throttle.

So it still stands probable that the props I bought are at least somewhat undersized for this motor right?
 
CarolineTyler

CarolineTyler

Legendary member
John_W said:
Thanks, yes the 1045 is definitely oversized, after running it on 9A for about 15 seconds the base of the motor that the windings are attached to was uncomfortably hot, not enough to burn skin though.

Running the 5045 4blades on it on full throttle 6.5A I cannot measure above 30°C (86 F) anywhere on the motor even after continuous run on max throttle.

So it still stands probable that the props I bought are at least somewhat undersized for this motor right?
Click to expand...
By that temperature I would say the motors can take a bit more maybe a 6045 three blade - maybe a 6050 three blade. Without full motor data its difficult to be say until you try it.
 
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