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  • Dave April 13, 2014 at 7:34pm
    Mine seems to do the same thing. When i first take off the failsafe goes off. I see my arming light start flashing and the alarm buzzer goes off. I turned off current monitoring but it still goes off.
  • Moderator
    Graham Dyer April 12, 2014 at 11:50pm

    It may be triggering on mAh used as that that limit may be hit before the actual voltage?

    • Charosenz > Graham Dyer April 13, 2014 at 9:14pm

      Graham, Dave,

      Thanks guys for the feedback.

      I too wondered if it was tied to the current and not voltage.   I have mine current set to trigger at 1/2 an amp which is the lowest value you can use and I know it was not down to that value when the FS shows up.

      You can see that the ship still flies after the FS BATT triggers because I don't have the FS BATT enabled, but it still goes in to automatic "LAND" mode fairly shortly thereafter.

      Dave,

      I do not see the FS at the beginning like you have described, but it does make you wonder what is going on with the FS functionality??

      Also, I moved my BATT value to 5000mah even though I really only am using 4500mah and todays flights did not see the FS jump in too early, but then again, I did not push it too hard.  So I will work on it more later.

      • Moderator
        Graham Dyer > Charosenz April 13, 2014 at 9:59pm

        The mAh setting should be set to the total capacity of the battery used, if you set it to "1/2 an amp" (500mAh) it will warn when 400mAh has been used up (500mAh - 20%) which will definitely give you an early failsafe.

        Set it to the capacity of your battery and the percent to 20% then you will get a failsafe after 4000mAh is used up, this is the recommended 80% that a 5000mAh LiPo should be discharged to.

        If you discharge more than 80% you run the risk of shortening the life of the battery or even irreversibly damaging a cell.

        • Mike J > Graham Dyer March 4, 2015 at 5:29pm

          I'm sure it's easy enough for most to understand, but can I ask again, what should the Reserved MAH be set at for a 5100 mAh 3S so it triggers a warning?  I had an auto land w/ no warning today and when I checked the logs it showed; Test: Event/Failsafe = FAIL - ERR found: FS_BATT

          • Greg > Mike J March 5, 2015 at 7:34am

            20% of the total as was stated earlier.  I your case 1020 is close enough.

            • Mike J > Greg March 5, 2015 at 5:30pm

              Thank you Greg.  Just needed a check. 

        • Charosenz > Graham Dyer April 14, 2014 at 10:34pm

          Graham,

          Thanks.  A few clarifying questions.  It has a place to enter a low voltage.  I entered 9.8 for my 3 cell lip.  It also has a place for the reserve amount of amperage you want to keep before FS triggers, which I set for half an amp.  on a 4.5 am battey this is about 10%.    But  20%  is .9 amp,   and having in lower, like .5 amp should not trigger it without it getting that close and with 10.65v still left I am sure I was not where near expending 90% of the battery.  

          If I am missing something please help me understand better what you are talking about. 

          • Charosenz > Charosenz April 14, 2014 at 10:38pm

            Graham,

            I think I just realized that there are other battery warning settings on the power module site that probably need to be reviewed.    I hope to get to that this weekend.

            http://copter.ardupilot.com/wiki/common-measuring-battery-voltage-a...

            Thanks.

            • Moderator
              Graham Dyer > Charosenz April 14, 2014 at 10:50pm

              The voltage should be set at 10.5v for a 3 cell LiPo, 9.8v is already in the part of the voltage curve that is dropping very rapidly and you will not have much power left. Typically you won't be able to stop a descent if the battery is at 9.8v.

              AMPD14_DischargeCurve.jpgYou need to specify whether you're talking about amps (current) or amp-hours (capacity).

              The wiki is a little out on what the voltage should be set at (I've edited it now)

              Remember there is a "battery failsafe voltage" (http://copter.ardupilot.com/wiki/battery-gps-and-gcs-failsafes/) to be set and a "MP alert on low battery" to be set

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