Sputtering motors at high load and fresh battery

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Eggplant
Posts: 6
Joined: Fri Jun 22, 2012 2:34 am

Sputtering motors at high load and fresh battery

Post by Eggplant »

Hey folks. I'm hoping someone has some ideas here.

I'm having a problem with one (or possibly more) motors "sputtering" under high load. Changing directions hard, high throttle when falling, etc.

Some points of interest:

  • NTM 1200 kv motors
  • HK F-20 ESCs flashed with simonk
  • 3s battery
  • Quadrino Zoom 1E
  • running 2.0 release with the config posted on the quadrino site

I've adjusted and calibrated everything. It all runs super smooth. baro, acc modes work flawlessly. No drift. No yaw. Very solid. However, on a fresh battery, under high load one or more motors will sputter usually resulting in a crash unless I'm at high altitude and can recover.

The most interesting part is that the problem goes away completely as the battery drains. After flying for maybe 5 minutes I cannot get the issue to recur until I swap out for a fresh battery. I've been able to reproduce this with regularity over the span of about 10 flights and three different batteries.

Also, I cannot get the issue to happen on the ground. I can hold the copter down and floor the motors and they spin solid. It only happens in flight, and only on a fresh battery.

Any ideas? It's driving me crazy.

mr.rc-cam
Posts: 457
Joined: Wed Jul 27, 2011 11:36 pm

Re: Sputtering motors at high load and fresh battery

Post by mr.rc-cam »

Tough one. But just to throw a curve ball at you, don't limit the investigation to the obvious things affected by a fresh charged battery. Maybe it is something totally unexpected.

For example, I spent several days chasing down randomly sputtering motors. The problem would move from motor to motor, without warning. And it was very intermittent.

It was the bullet connectors on the motors. They looked good, tested fine with a meter, but under the heavy currents (which are highest on a fresh charge) their inadequate crimped-ferrule design would not do well. I can't say enough on how visual inspection of the connectors does NOT help find this problem.

So first thing on the list (if you are using bullets on the motor<->ESC wires) is to get rid of them and use hard-soldered connections. Even if it does not help, your model will be better for it.

- Thomas

Eggplant
Posts: 6
Joined: Fri Jun 22, 2012 2:34 am

Re: Sputtering motors at high load and fresh battery

Post by Eggplant »

I'm using bullet connectors between my power bus <-> ESC <-> motor. I hate to redo all that but I'm running out of ideas.

I'm also using EC3 connectors on the battery with 12AWG wire, and those are the same bullet connectors inside. I understand they are rated up to 80A. I thought these were pretty standard?

mr.rc-cam
Posts: 457
Joined: Wed Jul 27, 2011 11:36 pm

Re: Sputtering motors at high load and fresh battery

Post by mr.rc-cam »

Until I saw it for myself, I never thought the bullets would cause any trouble. There's a couple other fellows on this forum that have also been bitten by this issue.

The connectors certainly look robust. But If you tear the plug side apart you will see it is actually two pieces swagged together. That is the Achilles' heel.

Of course this may not be your issue. But your model will be better without the bullets.

- Thomas

GoFaster
Posts: 5
Joined: Sun May 27, 2012 12:20 am

Re: Sputtering motors at high load and fresh battery

Post by GoFaster »

Are you the same person on RCG who is having the same problems with the same motor/ESC combo?
If so, SimonK replied that it's a sync loss issue.

Eggplant
Posts: 6
Joined: Fri Jun 22, 2012 2:34 am

Re: Sputtering motors at high load and fresh battery

Post by Eggplant »

Hi! I did post on RCG in the quadrino thread, but I don't see a reply from him there. Can you link it?

EDIT: Yes, I think I found it, but it was a different user than me. Same ESC/motor combo though! This seems to describe my issue:

http://www.rcgroups.com/forums/showthre ... st21959506

mr.rc-cam
Posts: 457
Joined: Wed Jul 27, 2011 11:36 pm

Re: Sputtering motors at high load and fresh battery

Post by mr.rc-cam »

This seems to describe my issue:
http://www.rcgroups.com/forums/showthre ... st21959506

Now that is interesting. I'm using Simonk's ESC firmware (downloaded June-1-2012) on my 450 Quad and it flies great with MWC V1.9. But with V2.0dev I have experienced exaggerated pitch/roll during aggressive movement. But since it does not happen with V1.9 I don't know if I can blame the ESC code, but will certainly keep that in mind. For sure, it will be interesting to see how your problem is solved.

- Thomas

Eggplant
Posts: 6
Joined: Fri Jun 22, 2012 2:34 am

Re: Sputtering motors at high load and fresh battery

Post by Eggplant »

I'm going to try the wii-esc code. I'll also likely minimize the number of bullet connectors in my setup after that. I'll report back.

Eggplant
Posts: 6
Joined: Fri Jun 22, 2012 2:34 am

Re: Sputtering motors at high load and fresh battery

Post by Eggplant »

I reflashed my HKF-20 ESCs with the Mystery20A_nFET wii-esc firmware, and after an initial flight test it seems my problem is solved!

I want to test more. I had gotten to the point where I could reliably replicate the issue. After banging the copter around pretty hard with the wii-esc firmware I was unable to get the motors to lose sync, but I've only had a single flight.

mr.rc-cam
Posts: 457
Joined: Wed Jul 27, 2011 11:36 pm

Re: Sputtering motors at high load and fresh battery

Post by mr.rc-cam »

Awesome!

- Thomas

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