• *
  • 7
Interesting Bench Test
« on: February 18, 2016, 10:13:08 pm »
I recently did a bench test on my Eachine Racer 250 with props on because it has been mysteriously loosing power causing it to fall from the sky. I'm new to all this and have been tweaking various settings in Libre so I was unsure if it was a setting which I would think cause consistent failure or hardware.

Anyway, I secured the frame and fired it up. Sure enough, when I started getting more aggressive on the throttle it completely shut down. I did the exact same test but with a different battery and it did not fail. Put the other battery back in and it failed again. Conclusion: Bad Lipo! I'll dispose of that faulty battery properly and generally feel good about myself for diagnosing the issue.

BUT!, I did notice something else during my bench testing. It seems that when I throttle up to say 20-25% and leave the stick without movement, the motors continue to speed up, turning faster RPMs. Soon enough I'd say they would be at 50% with the stick still remaining at 25%.

Any ideas what might be causing this? When setting up Libre I used the wizard and kept everything at default setting as it suggested without knowing any better. I used QAV 250 for the like quad for the PIDs. Did I set up the ESCs incorrectly? Here are the specs on the motors and ESCs.

Brushless motor: 2204 2300KV
Brushless ESC: Simonk 12A

Thank you!



  • *****
  • 4572
    • LibrePilot
Re: Interesting Bench Test
« Reply #1 on: February 19, 2016, 12:32:44 am »

That a normal behavior, the board try to correct the small error because is not perfectly level.
After some time the "I" term (from PID stabilization) accumulate the error so motors rpm increases without Throttle changes.


Re: Interesting Bench Test
« Reply #2 on: February 19, 2016, 03:23:15 am »
Yeah I thought the same thing. I noticed it did it in attitude mode but I tried it in rate and it stays exactly where you put it. It's trying to level itself and since its tied down it can't level where it wants to and it keeps trying harder and harder. Same with it just sitting on the ground idling with low throttle. It'll steadily increase. But not in rate mode. Or at least very very slowly so you never notice it (seems to stay right where you put it).

With the battery issue. Was it internally shorting out? Dropping a cell?or is it the battery's connector being loose?  You fixed the problem but do you know why the battery caused the problem. What was wrong with it?
5" alien 4s 596grams with battery and GoPro FPV
Lantian LT210 4s 604grams with batt and GoPro FPV
GE X220 4s 6" 513grams with batt and HD cam FPV
Homemade acro X copter. 6" 4s - like a warpquad LOS

Re: Interesting Bench Test
« Reply #3 on: February 19, 2016, 07:41:54 am »
I had the same issue. a bad battery, especially a 2s cant sustain the voltage high enough under high load and if it drops to low your ccc3d will shut down.


  • *
  • 341
Re: Interesting Bench Test
« Reply #4 on: February 19, 2016, 10:25:16 am »

I would also guess that it's a battery issue. Some ESCs are programmed so that at certain voltage level they either cut or slowly shut down the motors, to prevent damager from the battery. Worse would be if the battery voltage drops to a level that the motors cut out. In that case you can assume that the battery hast got some kind of damager, either before or from the incident.

best is to always use a battery checker to see if your batteries are ok. There are two kinds for daily use: one is like this one:

I always have one of those with me when flying.

The other kind is connected to the battery during flight and gives you alarm when voltage drops under a certain (preselected) level:

before buying those through those links I gave, check if you get better prices anywhere else, i just put them in for quick reference, no recommendation.

There are several reasons how batteries can fail: too low power: too small S-count and/or too small C-count, bad cell in the battery. Sometimes batteries are not or not well conditioned when you buy them. For that case I always do a few very careful flights, making sure not to draw too much power from the battery and that the voltage never drops below 3.6V per cell. After a few flights they are properly conditioned and can be used with no further issues.
Nighthawk 250, MT1806, 12A ESC OneShot125, Revo, M8n GPS, FPV
Cinetank MKII, Elite 2216, 30A Afro OneShot125, Revo Clone, M8N GPS


  • **
  • 50
Interesting Bench Test
« Reply #5 on: February 19, 2016, 02:39:49 pm »
Yeah to echo cato's thought I immediately wondered what the C rating was on the lipo.  What are the specs on both batteries?
F450 Quad Clone
Outrunner1000KV Motors
HobbyWing FlyFun 30A ESCs
1045 Props
Telemetry via OP Link
FlySky FS-i6 transmitter w/ 10 channel mod
Sparky2 Flight controller
Running LibrePilot next branch
FlySight Spexman FPV Goggles
Floureon 5500mAh LiPos