Quadcopter motor fails beyond 50% throttle

Question

I have recently build a quadcopter with the following specs:-

1. KK mini board
2. 4 x A2212-1000kV / 13T motors
3. 4 x 30A ESC
4. 2200mAh 25C 12.5V battery

The issue i am facing is that once the throttle crosses close to 50% either:-

1. One or more motors would stop spinning.

   Motor fail video 1

   Motor fail video 2

2. All motors would slow down to min speed.

I have checked the battery voltage before running and its at 12.2 V.

It would be really helpful if you could suggest a fix.

Thanks

---

Additional data

Voltage across ESC with motors (All 4 connected at same time w/o propeller) STOP => Speed at which motor stopped working.

          +---------+---------+---------+---------+
+---------+ Motor 1 | Motor 2 | Motor 3 | Motor 4 |
|Throttle | (Volts) | (Volts) | (Volts) | (Volts) |
+---------+---------+---------+---------+---------+
|   Min   |  10.3   |  10.3   |  10.3   |  10.3   |
+---------+---------+---------+---------+---------+
|   7%    |  9.75   |         |         |         |
+---------+---------+---------+---------+---------+
|   50%   |  9.48   |         |  STOP   |         |
+---------+---------+---------+---------+---------+
|   72%   |  9.26   |         |         |         |
+---------+---------+---------+---------+---------+
|   Max   | STOP /  |  9.28   |  9.28   |  9.28   |
+---------+  9.28   +---------+---------+---------+
          +---------+                              

Voltage across individual ESC with motors without propellers

          +---------+---------+---------+---------+
+---------+ Motor 1 | Motor 2 | Motor 3 | Motor 4 |
|Throttle | (Volts) | (Volts) | (Volts) | (Volts) |
+---------+---------+---------+---------+---------+
| Battery |  12.04  |  11.60  |  11.60  |  11.50  |
+---------+---------+---------+---------+---------+
|   Min   |  11.89  |  11.60  |  11.54  |  11.35  |
+---------+---------+---------+---------+---------+
|   7%    |  11.86  |  11.60  |  11.51  |  11.31  |
+---------+---------+---------+---------+---------+
|   20%   |  11.83  |  11.61  |  11.49  |  11.29  |
+---------+---------+---------+---------+---------+
|   50%   |  10.77  |  11.56  |  11.41  |  11.24  |
+---------+---------+---------+---------+---------+
|   72%   |  11.63  |  11.47  |  11.25  |  11.06  |
+---------+---------+---------+---------+---------+
|   Max   |  11.57  |  11.50  |  11.17  |  10.98  |
+---------+---------+---------+---------+---------+
+---------+---------+---------+---------+---------+
|Change in|  0.32   |  0.10   |  0.37   |  0.37   |
| voltage +---------+         +---------+---------+
| between |         |  Maybe  |                    
| 1st and |         |  error  |                    
|  last   |         |  while  |                    
| reading |         | taking  |                    
+---------+         | reading |                    
                    +---------+                    

NOTE: That after re-soldering, the motors run fine to full throttle without propellers. But once I attach the propellers the motor 3 stops spinning beyond 50% throttle.

Answer 1

This issue might be caused by a voltage drop accross the system. Either your batteries aren’t charged up, your batteries are rated for a lower voltage or, the way the power is being distributed is incorrect.

Steps to fix it:

• Check each motor separately: connect the three wire lead coming from the ESC and plug it into the receiver (motor must be connected to the three phase cables, and ESC must be connected to the battery). If any motor starts to stutter or stall, swap the ESC and check if the ESCs are defective.
• If the motors and ESCs are working correctly, check if your power distribution board is working correctly. If you’re using a power distribution board, then check each solder pad and see if there’s enough contact, also check each of the 4 ESC terminals are being supplied around 12 volts. If they aren’t being supplied 12 volts, then your pdb is at fault.
• If there are no faults with the motors, ESCs and PDB, check all your wiring and see if there’s any loose connections and also check the settings on the KK flight controller.
• For the KK flight controller, first, calibrate the ESCs, REMEMBER TO TAKE ALL PROPELLERS OFF. After calibration, go through the different settings to see if there’s anything to be changed.

During this test ALL PROPELLERS MUST BE REMOVED. After removing, you can take a small cut of electrical tape and stick it onto the motor shafts so you can feel the motor directions.

I personally don’t really like the KK flight controller because when calibrating the ESCs, a lot of things can go wrong, press the buttons for too long or too short, the motors will start spinning at full throttle. I’ve had personal experience when I left the props on and held the buttons for too long. I ended up with a shaved finger and two deep gashes near my right hand wrist.

If you’ve tried all of this and it still fails, please reply with a list of all of the components used.

Best of luck,

Sid.