Crash caused by battery failsafe problem?

I have been struggling with getting meaningful warnings about low battery. Thus, I have installed a small panel with 3 LEDs; one for arming connected to pin A7, one for GPS connected to A6 and the third for low battery connected to A5 (I wanted to use a LED instead of a beeper).

In MP, I set the LED_MODE to 11 and turned on the Battery failsafe with action to land. (see pictures).




When testing this a few days back, I kept the hex at a low altitude (to avoid fatal crashes). I have also installed a FrSky battery monitor so I can see the voltage on the radio.

When I was getting close to the low voltage alarm I had set on the FrSky, I suddenly saw the arm led on the hex blinking. Probably because I had reached the low voltage set in MP. After a split second, the hex leaned over about 45 degrees and crashed into some chairs. Fortunately only some propellers and the GPS pole was damaged.

If someone could provide some help on the 2 issues below, I would be very grateful.

  1. I have tried to analyse the log, but I have to little knowledge about it. I can see in line 2908 that I get ERR 6 and that MODE is set to Land in line 2907 (the line before ??).
    But why does the hex lean over and crash?
    I have attached the log below. Any help on looking at it would be very much appreciated.
  2. Regarding the low voltage alarm, I would just want to get an alarm at a specified voltage so I can land manually. And why does not the LED connected to A5 light up when I reach the limit? 

2014-11-24 08-12-24.log

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  • I recently had a sudden lean over, flip and crash on my Y6B running 3.2 on Pixhawk.  I was in a low hover, testing the new firmware, in PosHold and it just flipped over.  No Failsafe but a similar crash.  This might not be related to you issue but it seems very similar to me.

    After looking at the log it appears that the front left motors suddenly dropped so I suspect an ECS or sync issue.

    My concern is that there is a few people mentioning sudden rolls so I wonder I there is a more in depth problem.  My first inclination is to say that it is not a firmware issue but a hardware one.  However, if a Fe people are seeing uncommanded rolls and flips then maybe there is a problem.

    I am running 3DR ESC's with SimonK firmware.  Could there be an issue with sync in the latest release?  Not a code problem but a hardware combination?  Do we need to have a specific version of the ESC firmware to avoid this?

    I will test some more when I get new props.

  • Are the low voltage cutoffs disabled on your speed contollers? I havent looked at your log but maybe the LVC is starting to kick in on the ESCs

    • I'm sure I had no loose props as they are fixed with a 3 hole mount.

      Embarassed to say that I have not checked the Low Voltage Cutoff on my ESC. However, I'm using the HobbyWing Platinum Pro 30A ESCs. The factory default for these are "Middle" and I have not changed it.

      I'm waiting for new propellers before I can do any more testing.

    • good guess,  right before it rolls over, it hits a record-low of 3.59v/cell (most likely a 6s setup),  it's too high for a cutoff, but might be a very high soft-cutoff ?

      • I am sure that is not cause. Neither props or any other mechanical failure in my case. All my props tightened and ESC cut off is set to 2.8. My log attached.


  • not enought data to be sure, but it looks like some stick banging just before the roll fails, - I would a prop got loose or something like that ?


  • I haven't see your thread before i posted mine, but i have exactly same problem in this disscusion . I have just compered our logs. Same thing happen. Crash after failsafe and going to land mode.

    Your log:


    My log 


    They look to me almost identical:

    I think main problem here is not about low battery warnings but why did copter lean and crashed after entering land mode instead of doing what it should do and that is LAND.

    • Very interesting that you have the same problem. I have experienced the same "lean over and crash" before also, but then I was even less experienced and did not look at the log.

      As I mentioned in my first post, I saw the arm LED blinking just before it leaned over. My conclusion was that this was a low voltage alarm and that this failsafe situation made the controller take some action. The log tells us that the action was to land. Maybe it's the land function that does not work. Maybe we should try to put it into "Land" mode manually, with a fresh battery and see what will happen then ??

      However this is a bit scary. The last crash cost me 70$ and that was a "lucky" crash.

      Waiting to hear your opinion.

      • In my opinion autopilot did what it supposed to do in failsafe situation and executed land but what is caused to roll or in my last incident pitch is unclear. And you are absolutely right about safety of LAND mode. For now i turned of all my failsafe action except for Throttle FS = RTL and in case of GPS loss action is althold. For battery i have battery tester beeper.  

        Test: Autotune = UNKNOWN - No ATUN log data
        Test: Balance/Twist = GOOD - 
        Test: Brownout = GOOD - 
        Test: Compass = GOOD - No MAG data, unable to test mag_field interference

        Test: Dupe Log Data = GOOD - 
        Test: Empty = GOOD - 
        Test: Event/Failsafe = FAIL - ERRs found: FS_BATT FLT_MODE FS_THR 
        Test: GPS = FAIL - Min satellites: 0, Max HDop: 99.99
        Test: IMU Mismatch = UNKNOWN - No IMU log data
        Test: Parameters = GOOD - 
        Test: PM = FAIL - 81 slow loop lines found, max 13.76% on line 22084
        Test: Pitch/Roll = FAIL - Pitch (-272.29, line 45438) > maximum lean angle (45.00)
        Test: Thrust = GOOD - 
        Test: VCC = GOOD

  • i dont rely on the arducopters ability to tell me voltage i got the telemetry for it and a beeper and i use time intervals... for some reason the apm does not get accurate readings.. its even caused it to land well mine far before its time is due like within 2 minutes of a fresh battery when it flies 8 minutes.. or more

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