Ralgh

I was flying my plane at a high power setting and the motor cut out. It was a reasonable amount of flying time for the BEC to kick in. Once the plane started to glide I realized I had no control of it. I pulled the throttle all the way back and still no controls were working. Fortunately the elevator was full up and the plane is very stable. It just kind of did a slow wings level much into the grass and there was minimal damage. When I got to the plane every control surface was now at full deflection. And one servo had been rotated 180 degrees from the crash. It was fighting me when I tried to straighten it with my hand. Also I could hear one of the other servos buzzing as if there was a slight load. There seemed to be power going to the servos but they would not respond to any movements of the sticks. I disconnected and then reconnected the battery and everything worked again except the servo that got rotated 180 degrees wouldn’t center where it used to. I might need new gears for that one.

I am running a Hacker B20 15L motor with a Phoenix 25, a Thunder power 11.1v 2100Mah battery, APC 11X4.7 prop, Hitec 555 receiver and HS55 servos. The battery showed about 11.3v when I hooked it up to the charger and it only took 1500Mah of charge. My other battery took a lot more when I charged it after a normal flight. That was the first use of each battery.

Before I flew it I was having a power problem. With a battery that was about 11.8v the motor would cut out at three quarters throttle. I checked the voltage and it would drop to 9v when the motor would cut out. That seems like a big drop to me but I don’t know much about this. I talked to a guy who has a similar setup and had the same problem. He called Castle Creations and they just said the new firmware is more precise than before and to just set the cut off voltage lower. My first battery behaved normally but the second did not.

With all that does anyone know why my radio would have cut out with the motor yet still have power going to it? And even more strange just start working after I reconnected the battery. I am afraid to fly it again because the consequences could be a lot worse if this happens again.

Matt Kirsch

My Feedback: (21)

In regards to the power problem, it sounds like the ESC is working as advertised. You want it to cut out at 9.0 Volts when you're running a 3S (11.1V) LiPoly. That's 3.0 Volts per cell. Run it any lower, and you will cause damage to the pack.

When a pack's voltage drops drastically like that, it means you're drawing more current than the battery can handle. Since you have another identical pack that's handling it fine, I would first suspect that the pack that cut out might be a bit weak, possibly damaged, possibly bad from the factory. Call ThunderPower customer support on that one.

As far as your glitch... I don't know if anyone can say for sure what the issue is. You might want to send the ESC back to Castle, and the receiver back to its manufacturer to be checked out. It may be that the BEC truly "kicked in" when you hit the low voltage. You want the LVC to kick in, not the BEC. The BEC powers the receiver, hopefully all the time, while the LVC cuts off the motor when the low voltage limit is reached.

You did say that you were running at a high power level. This is just a theory, but perhaps the heat buildup was an issue?

Ralgh

On another forum it has been mentioned guys have had the same thing happen with a servo binding up, a bad servo and overheating the speed control. Of those things it seems most likely it is an overheating ESC. The motor was hotter than the first flight and so was the battery. The ESC may not be geeting enough cooling where it is mounted and in addition it is right next to the battery so it may be transferring heat. According to Motocalc this set up is drawing very near the limit of my motor. I was doing a hover when it happened so that would be a high power draw situation. I am going to open up the cowl some more and move the ESC into definite direct airflow and hopefully this won't happen again.

elevation

The BEC (battery eliminator circuit) in the ESC ( electronic speed controller ) is a voltage regulator which supplies current to the receiver and servos. Most voltage regulators will cut out when over heated due to too much current. Many are rated for 2 or 3 amps. The actual cause of this could be due to to a bad servo or too many servos drawing too much current. It doesn't explain why you still had power. If the receiver dropped out you should have also lost power from your ESC to your motor.
I agree that you should have each device checked out and or try substituting each device until you locate the source of your troubles. Good Luck

Ralgh

I have a prop that is one inch shorter and the same pitch. I ran the numbers on that and it is supposed to draw about 2.5 fewer amps at full power. I have also reset my low voltage cut off back to 9v. Do you think that would help if I was running too many servos? Any suggestions on how to test a servo to see if it is a problem? I tried a bunch of things including blocking each servo from moving trying to duplicate the problem. So far it hasn't recurred.

I did notice that when I had a fully charged battery (Thunder Power 2100) and the ESC low Voltage Cutoff set to 7.5 and the 11X4.7 prop the motor slowly lost RPM and quit in less than ten seconds. The battery was warm after the motor quit. I did the same thing with the new setup 10X4.7 prop and it ran longer and the battery was still cool. It actually never hit the cut off, I just throttled back. There may have been a slight decrease in RPM but it was minimal.