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Battery sudden drop miracle

Discussion in 'Inspire 1 Discussion' started by Machoman, Nov 7, 2015.

  1. Machoman

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    Everyone has heard about the battery sudden drop cases. Conclusion of reports in different forums is:

    Batteries started below 100% can sudden drop to 0% if
    a) they have not been fully charged
    b) they have been charged some time ago
    c) they were used twice and removed from the aircraft between

    I want to have a more close look at c) because its not obvious why this happens in that case. a)+b) its just possible they had already low or even lower voltage then % shown.

    But HOW does a battery flewn from 100% 4,3v--> 60% 3,8v which is removed then and just a few hours later used again loose the voltage in the meantime so that it shows 60% but may have only 3,5v left so it shortly falls to 0% then. The voltage is always shown correctly.

    Is this normal for a healthy battery or does this case already show a faulty battery itself?

    As I had this case with always the same battery which also started to get major deviations and voltage warnings my conclusion would be that this sudden drop will not happen generally with all batteries but be the first indication of a faulty battery.
     
  2. The Editor

    The Editor Moderator
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    OK - you have asked a sensible question. :)
    The reason is simple.......
    Every battery will drop its voltage under load. Once this load is removed the pack will recover slightly and 'bounce back'
    The Inspire takes its percentage calculations based on an algorithm of mAh used from the pack and voltage.
    When the battery is fully charged and starts to be used the voltage will track under load with the depletion of the pack.
    However, if you land and turn off the battery at say 3.6v per cell after a few minutes the pack will recover and the the battery may bounce back to 3.8 or 3.9v per cell. The next time you insert this battery, the Inspire will take a voltage reading and assume the pack is more charged than it actually is.
    This, then corrects itself in flight after a few minutes resulting in a sudden drop off of percentage as the Inspire sees a larger voltage drop than expected over a shorter period of time.
     
  3. Machoman

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    But then it would change the % shown. If I stop at 60% and it would think its more charged like it is at restart then it would show 65% instead. But it doesnt. It continues exactly there where it stopped. Only the voltage have decreased in the meantime and its needs some time to realize.

    There is not a recover in the break its the opposite the voltage goes down more. And thats the miracle where I think its the first sign which points to a faulty battery.
     
  4. The Editor

    The Editor Moderator
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    No....ALL lipos will bounce back after having their load removed, they will never drop....Its battery chemistry and physics.
    Additionally, you cannot accurately measure a percentage of charge from a voltage reading on a lipo - they will all differ and it is a very inaccurate to get a reading based on voltage alone.
     
  5. m00se

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    Perhaps you could measure the voltage with a voltmeter when you shut down at 60%, then measure it again when you want to make the second flight.

    The Lipo should react as Editor says, there should be a voltage bounceback when load is removed.

    If you see a voltage of say 3.9 in the app under load, then after a couple of hours the voltage with no load has dropped, then I would start to worry about my battery.

    As a general rule you should only fly with 100% charge. Even "dumb" batteries from other systems should only be flown with 100% charge. I personally only fly my other packs from other machienes down to 3.7v a cell, (I actually use 22.2 total pack voltage and have to hope there isnt an inbalance) some people would suggest that I have only used half the pack, I dont consider that to be true, I may have only used half of the voltage range, but the pack is only safe to fly down to about 3.4v per cell. And the voltage drop from 22.2 to 20.4 is pretty quick.
     
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  6. Machoman

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    But exactly thats the point here or the voltage drops very fast in the moment switched on. It has been reported this does not happen if the battery stays in the plane but it does happen if it is removed in the meantime. So the question stays why it does this and I still think only faulty batteries do this.

    I often did this when in a short scenery the plane returns with 40-60% to use it for another short little later but the problem happend only with one battery and its the same one which gives me voltage warnings all the tim now under full throttle.
     
  7. Mike Mas

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    Until such time DJI addresses the problem the only way for reliability is after your done with a session, do not recharge the batteries until the night before or just previous to the session. This assures two things - no goofy self discharge routines and secondly fresh full charged safe batteries.
     
  8. Machoman

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    Thats ok but the question here is can DJI make a valid restriction like we are not responsible because you started with our battery at just 60% capacity and thats the reason it fell down after a minute? Can it not be expected that a battery showing 60% in NOT falling down after 1-2 minutes?Especially in this case where it has been used from 100--->60 only a few hours ago and not stored overnight or never been fully charged.

    I am only speaking of case c).

    And I see this as a faulty battery if it behaves like this it is just still unknown why it does it its probably not the same reason like in the other cases where it was stored a long time or has not been fully charged.