BEC and Launch Stutter

[nemethp13]

OK, I have recently upgraded my 2wd 1:10 ruckus with a Mamba Max Pro ESC and a Traxxas Velineon brushless motor (the ESC was purchased used and said to be in good condition and the motor was given to me by a co-worker that killed the Traxxas ESC and just bought a whole new hobbywing setup).

Anyway, the ESC came with a brand new external BEC. Since I haven't upgraded the steering servo yet I figured I wouldn't need to use the BEC. I have no idea if this is correct.

The problem, some times while bashing the car stutters when I pull full throttle. It is like the Receiver has lost connection to the Transmitter (the steering goes out and the car acts like there is no throttle input) for a second and then it kicks back in.

Would this most likely be the receiver/transmitter, or the ESC? I was reading things about the Mamba max esc's being suspect with Spektrum receivers (I guess noise causes issues) but I don't think this would kill the steering? Could the ESC be pulling so much power that it just drains the entire system for a second?

Any help or ideas would be greatly appreciated.

I guess I could pull the brand new receiver from my son's car and see if that stops the issue?

 

[i_r_beej]

To the best of my knowledge you shouldn't need a BEC. Most (if not all) ESC's for surface vehicles include so-called "BEC" and supply sufficient power to the rest of the system (servo, motor, etc). However, your idea that the system is experiencing a power/voltage sag (or "brownout") might have some merit.

Typically, high performance ESCs will include a capacitor (or a bank of multiple capacitors) that act to prevent these sorts of instantaneous power sags. The ESC you have may not have any capacitors or they might not provide sufficient capacitance for the car's power system.

I use HobbyWing ESCs in all but two of my cars (both are brushed systems) and they all feature a capacitor component (my racing cars each have cap packs of four capacitors.)

Another thought: Is the motor sensored or sensorless? If sensored, I'd also check the sensor wire. In a sensored motor system, a faulty sensor wire can cause "stuttering" when applying throttle. Typically at low throttle but if you're punching it, you'd also experience some stuttering.

Good luck and let us know how it goes.

 

[Steve g]

Definitely try another reciever. I havent had issues with castle and spectrum, but i also never had that specific esc.
Since you have the bec already, hook it up and see if it fixes it. Seems like it could be a reciever power issue, those older cc escs have weak becs, was a common complaint. New ones push out 8 amps(at least the mamba x and mmx). Normally i would think it would be enough, especially for a stock servo on an ecx, but since you bought it used maybe it has a interal bec problem already, and that's why it came with a external bec?
Also check that all connections everywhere are clean and snug. I apply penetrox/nolax on every connection from the battery to the motor and the reciever. A tiny light coat is all that's needed. It'll stop any corrosion and lower the resistance of the connector. It can be bought at any electrical supply store, or home improvement store (homedepot, lowes) in the electrical section.

 

[weave]

Namethp13, I just experienced the same thing on my brushless Torment and throught that I had depleted the battery. I took back in the garage put it on the work bench, pulled the body and proceeded to disconnect the battery. While disconnecting the battery the ground wire came off the Dean's plug on the ecx. The only thing that was holding it on was the shrink tubing which was causing intermittent power to the motor. Not saying that's your problem but good to check.

 

[nemethp13]

The BEC definitely helped but didn't fix it completely. I think it is good enough though. Need more time for bashing this week.