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Battery popped out when crashed? Theory: It was never in place!

Discussion in 'Pro/Adv Discussion' started by StumbleBee, Sep 16, 2015.

  1. StumbleBee

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    I've only been a member of this forum for a relatively short while, but I've read so many sad crash stories. It is very surprising to me the number of pilots who report that their batteries were found next to their crashed birds. Or that the battery was found to be partially ejected from the aircraft.

    Take a look at the latching mechanisms on the battery. There's no taper to them. When that battery is snapped into place those two laches have a death grip on the housing. That is in addition to the somewhat tight fit of the battery to the housing even without the latches.

    Now try pulling your battery out without depressing the latches. I've got a fairly healthy grip and can easily pull with at least 30 lbs of force. I could pull harder but don't want to risk damaging the frame. I can't budge that battery.

    So how is it that they are 'falling out' on impact? Assume for a minute that the bird falls straight down onto concrete and that it lands directly on the side where the battery ejects. The first thing that hits is two props, and then the two arms. How many G's are experienced by the battery after this somewhat shock absorbed worst case scenario? Ten? Fifteen, twenty? That means that up to 20 pounds of battery weight is pushing against those latches. I can't budge the battery with thirty. How can 20, in our worst case scenario, pop the battery out?

    My theory is that pilots are not ensuring that their batteries are snapped into place and that they are vibrating free. The tight fit? Easily overcome by a process similar to liquefaction of the ground during an earthquake. When high frequency vibration is induced into a surface it tends to greatly reduce the friction between any two components in contact with each other. Just as we saw in so many cases of runaway acceleration of cars, the drivers swear that their foot was slammed down on the brake when it was on the accelerator, I think pilots staring at the remains of their expensive birds are loathe to think operator error. It's human nature.

    Many of those crashed birds, I don't say all, lost power when the battery contacts finally lost...contact. No power...end of flight. Has anyone done a failure analysis taking a look at the data recorders of crashed birds for voltage just as the birds became unresponsive? It would have to carefully ensure at what point voltage went to zero. Did it go to zero at the precise instant of ground contact, or did it some seconds before? If it happened seconds before, that would seem to support my hypothesis.
     
  2. 4wd

    4wd

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    I suspect the main body briefly deforms and the latches can let go then.
    However it is quite easy to not fully click them home.
    I have one (of three) needs carefully checking every time as sliding in casually there will often be a 1mm gap.;
    It works OK but on one occasion there was some odd error message and sudden 'low battery' soon after taking off.
    I'd guess the power was getting through but the data pin connection was borderline.
    It continued to fly normally and I landed and then saw the issue.
     
  3. robsquad

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    the shell probably flexes upon impact making the tabs useless
    the front arm lights are a good indication of it the bird had power or not if video was running
     
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  4. BigKenny

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    Get a high frame rate camera and do a CSC in flight... you will see why the battery pops out at impact. It's not user error! (I think the flexing shell and battery momentum theories are correct)
     
    #4 BigKenny, Sep 16, 2015
    Last edited: Sep 16, 2015
  5. jasonb777

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    did a flight the other day and when I returned and hand catched I realized there was an 1/8 inch gap between the battery and the quad:eek: I was freaked out because I always double check eveything; obviously not this one day:oops:
     
  6. Oso

    Oso

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    Do you guys recall how many hundreds of posts we had a few months ago about people not fully seating their batteries?
     
  7. BigKenny

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    I do notice one of my batteries fits much tighter than the other. Either way, I am in the good habit of making sure I get a good click and check the battery seating every time. Of course, now that I say that...
     
  8. Buckaye

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    This... plus the weight of the battery X the speed at which the drone hits the ground probably produces a pretty good force... my experience with RC's is that batteries almost always pop lose in crashes.... doesn't surprise me at all that they pop loose on the Phantom.
     
  9. bobmyers

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    They will back out if they are not seated all the way in-- and if they back out over 2mm they will lose contact with the 2 small pins that detect the cell voltages which will cause a battery error and will shut down the motors at some point. There are several threads on this forum regarding this issue.
     
  10. Meta4

    Meta4 Moderator
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    And in crash situations where the Phantom doesn't fall out of the sky but hits a tree etc while under power ... the battery often comes out.
    Although the theory is possible, it's most often the symptom and not the cause.
     
  11. StumbleBee

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    Ummm...I'll supply the camera if you supply the P3P ;) While there is some flexing of the housing my visual evaluation says there is not enough to release the two lock tabs. YMMV
     
  12. StumbleBee

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    Agreed. And for those who aren't metric, 2mm is not much over 1/16"! Are you checking for a gap that small before each flight? How about when you pop a new second battery in so you can get right back up in the air?
     
  13. StumbleBee

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    Yes, I've also read that batteries have been ejected after colliding with trees or other objects. I don't attribute all crashes to batteries not being seated, and I don't deny there is some possibility of a properly seated battery popping out. I just think that the chance of that happening is minimal.
     
  14. Mal_PV2_Ireland

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    There were reports of 1St gen P3's having problems with 2nd batteries needing a good hand smack to be fully seated and there were a lot of reports of phantoms falling out of the skies but that could have been down to new owners doing a csc which we see every time a new phantom is released so it's hard to tell but since the p2/p2v and the introduction of the smart battery 9 out of every 10 decent crashes have always ejected the battery, nothing to do with it coming out mid flight.
     
  15. StumbleBee

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    Mal, I'm not trying to be argumentative, I'm trying to be investigative. How do you know that? What is the evidence?
     
  16. Meta4

    Meta4 Moderator
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    That fits with the reports that we see here and the one crash that I've observed.
    The battery commonly comes out in a crash.
     
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  17. Mal_PV2_Ireland

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    Ah I didn't think you were being argumentative at all mate, not in one bit. It's because I've had it happen to me over the years and I've been involved in so many threads here that it's just from experience. I like toubleshooting things, it's kind of a hobby because I like to get to the bottom of things and figure out why things went wrong. I only give honest opinions when it comes to stuff like this and that experience comes from asking countless questions in maybe each of 50 or more threads like this. Don't worry man I'm on everyone's side once it comes to figuring out a problem. Nevermind all the conversations I've had in here but I'd say everyone of 40 Irish fliers I know real well have all had a battery pop out on a p2 and p3 when they've crashed. It's just what happens. I just wish the p2v+ and p3 camera was similar to the p2v camera because when you had a crash that baby would roll like a golf ball 100ft away and wouldn't have a scratch on her
     
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  18. Mal_PV2_Ireland

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    But yeah I wouldn't worry about a battery coming out after a decent handshake with the ground. I've personally seen it at least 6 times out of 6 crashes straight to the ground, I don't mean slow branch crashes. Every hard crash I've seen that involves a phantom smart battery they always wound up being looked for
     
  19. Garrie

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    I guess there's only one way to find out! We need someone to sacrifice their drone for our investigation, too bad Mr Chinese-Man-With-Thick-Goldchain-and-Angry-at-DJI already hammered his P3.
     
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  20. dirkclod

    dirkclod Moderator
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    monker thumbup.gif
     
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