CC BEC Powering Motor Issue...
 

Hello,
I am tying to power a 27t 540 motor using a castle bec. I plug in the battery, hit the switch to turn on the motor and all that happens is the vibrates a little, like it's trying to turn, bud doesn't. I have the bec set to 4.8 volts and have tried higher but with the same result. The reason this beats me is because when I hook the same motor up to my variable power supply at 4.8 volts it draws 5 amps. The bec is rated at 10 amps max so I am not sure why I am having the problem I am. Hopefully someone here knows! Here is a pic of the setup too if that helps anyone.

https://i.imgur.com/gG4DXQjh.jpg?2

Re: CC BEC Powering Motor Issue...
 

Why are you using a BEC to do the job of an ESC?

Re: CC BEC Powering Motor Issue...
 

Seems like an odd application for a BEC but I assume this motor is running some tool or something and your just trying to get the motor spinning the right speed?

I wonder Is 10amps enough for a motor? also those tiny wires, can they deliver?

Re: CC BEC Powering Motor Issue...
 

Because I don't need to control the speed of the motor. And so that I can use a 2s or 3s or 4s or whatever battery I have on hand to power it. It's for a motor lathe btw. I guess I could have mentioned that lol

Re: CC BEC Powering Motor Issue...
 

That makes more sense, but it still doesn't make sense to me. :ror: I wasn't sure if you were some noob that bought a BEC thinking it was an ESC. That would have sucked.

I'm guessing the motor is drawing more power than the BEC can provide.

Re: CC BEC Powering Motor Issue...
 

Odd? yes, I suppose. In my mind it's just a voltage regulator and thats what I need it to do although it may not be just that. And yes, my goal is just to get the motor running the right speed.

I would say yes because when I had it running from my variable power supply and it was only drawing 5 amps. So in theory a 10 amp bec, voltage regulator, whatever should be fine. Also if the bec is rated for 10 amps then why would they put wires on it that can't handle the juice? I dunno... makes sense to me but maybe I'm missing somthing?

On second thought I suppose I could measure the current draw on it. That might be interesting to see.

Re: CC BEC Powering Motor Issue...
 

Haha nope:ror: That was my first thought as well. I will go measure how much it's pulling and report back.

Re: CC BEC Powering Motor Issue...
 

What switch are you referring to? can it handle the draw too? I'm guessing it can, I'm just throwing it out there.

Re: CC BEC Powering Motor Issue...
 

Did you hook the BEC up to the computer/programmer and set the voltage?

Re: CC BEC Powering Motor Issue...
 

There is a little pushbutton switch that is wired in line with one of the motor leads to turn it on and off. Yeah It can.

yes, to 4.8v

Re: CC BEC Powering Motor Issue...
 

It works for me but I don't have a switch on my setup. Does your battery got enough juice or maybe a bad connection?

Re: CC BEC Powering Motor Issue...
 

Did you try to hook the power supply up to the bec at a higher voltage like 7.4? I only use a power supply to run my lathe but out of curiosity I tried the same castle bec and it does work on mine.

Re: CC BEC Powering Motor Issue...
 

Huh. Does it really. That's interesting..... Yeah I was running 11.1 into the bec. Wait, how many turns is the motor in your lathe?

So I have some interesting findings. My dad (the electrical engineer) and I did some investigating and troubleshooting of all this. Here are some numbers as well.
https://i.imgur.com/x0avFzil.jpg

This is my variable power supply with the voltage capped at 11.1v and the motor switch is ON and running pulling the 2.4A or so.

https://i.imgur.com/Xr7mbArl.jpg

Here everything is hooked up identically to the picture in my original post except that the battery is being replaced by the power supply. The psu is capped at 11.1v with a 0.010 A draw from the bec itself and the output of said bec is being measured on the Fluke at 4.7v. The motor switch is in the OFF position.

https://i.imgur.com/1Ts5iKnl.jpg

Here's where things got weird. The motor switch is ON in this photo. PSU capped at 11.1v, 0.050 A draw, but the bec output has dropped to 0.02, basically 0 volts. My dad said that he suspects that that there is too much current being pulled so the bec cuts out (and the little green light on the bec goes out) however the power supply is capped at 5 A and the bec is supposed to be able to handle 7A continuously with a 10A peak so if the motor wants more power than the 5A then I should be able to see that it wants it. But I don't.

https://i.imgur.com/9xav5o2l.jpg

We then decided to hook it up to my oscilloscope for fun and see what the voltages were doing. Essentially what is happening here is that as soon as the switch is turned on, the bec goes into over-current and drops everything down. It sees the current has been lowered(in reality by it's own doing) and tries to kick back on, but goes into overcurrent again and shuts back off. That's what is happening on the right half of the screen with the pulses you see. Those pulses do continue on 'forever' and result in the motor making little pulsing vibrations like it wants to turn but can't.

My dad also says that voltage regulators use a feedback loop to do their regulating and depending on the way the circuits are designed, an inductive load can sometimes mess with that loop. Motors are one type of inductive load so that could potentially be the issue. That's a little over my head personally :roll: but what do y'all think?

Re: CC BEC Powering Motor Issue...
 

Over my head. Do you have another CCBEC to test?

Re: CC BEC Powering Motor Issue...
 

DC motors draw huge amps at startup.

Re: CC BEC Powering Motor Issue...
 

Yeah I do. I might try it today.

Hm. Well okay, I do suppose it makes sense. It probably takes a lot to get it to move but then once it does it doesn't need as much (I know that's basically what you just said) Ya know... I suppose the BEC may be able to handle 7A but not at the rate of flow that a motor would need to run. Between my analasys of the motor's amp draw and the specs of the bec, I should be able run the motor. So I guess that's why it would lead me to believe that its a rate of flow issue somehow. Logical? I dunno.:ror:

Re: CC BEC Powering Motor Issue...
 

Putting aside the question of using a BEC to drive a motor size it isn't designed for. Here are a few observations (probably creating more confusion!):
1. Why is the BEC output set to 4.7V? IIRC most 540/550 motor runs at 7.4V. Why not set the BEC to 7V? IIRC, higher voltage means drawing less current at startup? I'm probably wrong here, it's been decades since I studied electrical circuits!
2. I don't know the vertical scale on your oscilloscope but those peaks tell you the startup current draw of the motor. If those peaks exceeds the BEC peak output current (12A @ <5.25V with ~11V input according to CC: CC BEC 2.0 Voltage Regulator) then the BEC will obviously goes into over-current mode and 'stops'.

Re: CC BEC Powering Motor Issue...
 

What about using a UBEC instead would that work better? Sorry I have to pose that as a question because I just don't know but I have heard one member on here who recommends these as an alternative to a BEC

Re: CC BEC Powering Motor Issue...
 

I would try another bec. My set up has a 35t motor and that drew 8 amp on my power supply to start. I hooked this setup to an scx10 pushed it down held it back and with a 1350mah 3s lipo thing took off without stalling.

Re: CC BEC Powering Motor Issue...
 

I have my voltage set to 4.8v because the instructions say a 4 cell battery works perfect for the application. I am making the assumption that they are talking NiMH because I have seen other lathe setups that use a little 4 cell NiMH or NiCad battery pack so then 4 cells each at 1.5v equals... wait 6v. Welp I have no idea where I got my 4.8 number lol. Somewhere online I'm sure.

Veritcal scale is set to 1v per div and horizontal is 20 milliseconds per div. Ok, yeah what you're saying makes sense.

I have never heard of such a thing but after googling it, it seems like a possible solution. I did buy the ccbec just for this but I will need to get something else in the end I'm pretty sure. My gelande needs a bec so at least it won't go to waste.

Huh. Okay, interesting. I will swipe the bec out of one of my rigs and try it out. I will also try a 35t motor like you've got. What voltage did you have that bec set at?


Btw thank for all the help and ideas everyone!"thumbsup"