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Sudden Loss Flight Time and Auto Descend

Discussion in 'Phantom 2 Discussion' started by shartlza, Jun 5, 2014.

  1. shartlza

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    My flight time to 25% has always been around 17 minutes. Well, out of no where it started being 15 minutes and for some reason it starts to auto descend as well and the only way to keep it up is by giving it throttle. The auto descend should happen at the second level which is set a 15%, not at 25%. Also how fast are the red LEDs on 1st level because mine do blink fast, but not really fast? I really noticed the decrease in flight time after updating to the 3.04 firmware and doing the default gain button (which raised gains), but I am not sure if that is the culprit. I have a screen shot below of the assist software showing the battery. You can see I have only discharged it 69 times and the battery is at 77% life. Another thing I noticed is cell 1 is about 20mV below the others. I am not sure if this is normal, but I thought all cells should be closer to each other.

    So a few questions, and any suggestions or points would greatly!!!
    1. Is this normal to see the reduction in flight time at 77% battery life?
    2. Do the cells look normal?
    3. Anyone else notice a reduced flight time on 3.04?
    4. Do you think this could be a faulty battery?
     

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  2. N017RW

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    1) As far as 77%, that's something DJI is calculating and I have no idea how meaningful it really is.

    2) I don't think the cell im-balace is significant after discharge.This happens, that's why they are balance charged.

    But your resting voltage is 11.2. 11.1 is as low as you want to go (at rest).

    The 'current capacity' of 1200 further illustrates you have used ~80%.

    So it seems the battery is aging and what you are seeing is not out of the ordinary in term of some reduced flight time.
    Faulty???

    It would appear the V drop-off is so fast you never see the first warning and goes right to AD.
     
  3. shartlza

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    But my real issue is right at 25% it started auto descending and it has never done this. I understand 11.1 volts is the lowest you want to go and i never get there. The only reason it was at the 11.2 is because i had it on while plugged into the computer for about 5 minutes to see what was going on. I wouldn't think after only charging this battery about 70 time my flight time would reduce that much. I would expect that after about 150 or 200 charges and on top of that it would happen gradually and not so quickly. Last week i was flying 17+ minutes to first warning, then all of a sudden this week i get 15 minutes. Also this is only with a H3-3D gimbal, no FPV gear. Something just seems off. Maybe i will contact B&H (where i got it) and see if they can help me out.
     
  4. ElGuano

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    A 2 minute flight time difference could easily be accounted for with temperature, flying style, wind, etc. it may be harder for the flight controller to determine the battery percentage if you are throttling under load as well. Without FPV it's hard to see what the battery is reporting to the Naza in flight. But if you are really getting auto-descend at 25%, I'd recommend performing a calibration discharge so the battery is tracking its really health accurately; have you done this regularly?
     
  5. shartlza

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    The flight condition and flying style have been no different from most of my 17 minute flight. I did notice at about 14:30 when I throttled up the red lights started flashing, but as soon as I let it hover it stopped. Then right at 15 minutes they came on for good. Yes, I have done the discharge 3 time, since you are supposed to do it every 20 discharges.
     
  6. ElGuano

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    The p2 battery is quite likely to be a low-c pack (~10c) so it's very likely that you're seeing the effect of voltage sag when you punch the throttle near the end of the charge. That sag is enough to make it hit level 1 protection (LEDs flashing) and may be enough to make it hit level 2 (auto-descend). If it hits auto-descend, I think it is locked in, it'll stay on it even if the voltage sag condition is alleviated.

    So it could be that your battery isn't actually faulty, it's just getting triggered earlier when it's close to end of pack. There have been some people that have had this condition happen at 50-60% drain, that was a problem and those batteries got replaced.

    I would fly a bit more and see if it happens consistently, or when you are clearly not throttling.
     
  7. shartlza

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    I understand all that, but it has been doing this for the last 4 or 5 flights and it has actually lost about 10 second each flight. I wouldn't say i am punching the throttle for the voltage to sag. Even if I slightly give it throttle it would start to flash. In my last flight, that was 14min 30sec, I gave it slight throttle for about 2 seconds and it blinked red like twice, then i let it hover and about 5 seconds later it started blinking red and started auto descending, so it is not like i was hitting it hard enough to sag it all the way down to level 2. Right after that i plugged it into the assistant and the screen shot above was taken about 5 minutes after that and was at the 25%. I talked to B&H and they said since i was past 30 days with them, it would be a manufactures warranty and I would have to contact DJI, but they did agree it sounds like it could be an issue with the battery. I did email DJI, but we all know how that will go. I'm at a lose. I guess i will fly it and just know i have to bring it in closer to the 15 minute mark. The bastard better not go out mid-flight though!!! Time to start thinking about a second and maybe third battery. :?
     
  8. ElGuano

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    Yep, I get it. Yours is kind of on the borderline because it happens really close to the end of flight. I know of several people who have actually gotten their batteries replaced for similar behavior (though more for when it kicks in at the beginning or middle of flight) so it's definitely worth pinging DJI. But I don't think you are doing anything wrong with the battery, from your description.
     
  9. shartlza

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    Yep, thought it would not hurt to try. Even though I am sure if DJI gets back to me it will be a answer like, "This is normal for your current battery life." Whatever i guess, but if this does start to happen mid flight then i will start raising more red flags.
     
  10. erico

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    Hi
    I seem to be getting a similar problem but I put it down to something I was doing wrong as I still have not much flying time . The other day while flying my Phantom started to auto descend but on checking my battery level I still had over 30% ( I am just not sure how much as I was concerned about were it was trying to land.
    I took it home and discharged the battery and then recharged it . I noticed on the Phantom assistant that one of my cells is over 100mv different from the other two ( Cell 2) .
    Does anyone know if this is normal or should I contact my dealer or DJI for info ?

    Thanks

    I am using firmware 3.4
     

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  11. shartlza

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    Was your flight time the normal time you usually get? I really hope this is not a bug within the 3.04 firmware!! :x Has anyone else had these issues with 3.04 firmware? Is it possible to go back to 3.03 to see if this is fixed?
     
  12. erico

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    My flight time seemed to be a lot less but as I say I do not have more than maybe about 15 -20 flights so still learning and was putting it down to my flights tests .. ie sometimes just hovering and others pushing it out fast to 100 metres etc. I want to do more tests with my other battery and compare but just was wanting if anyone can comment on wither the cell voltage had anything to do with it .? I will try and take a average of flight times the next few flights with both batteries .
     
  13. shartlza

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    So here is a flight, that at 14min 15sec started to auto descend. http://youtu.be/pwNMV2QVUaw
    Then I went strait inside and checked the assistant and the below is what I saw. Really, 27%!!!!!! I know this is at a percent that I would be landing any way, but it should not be auto descending at this level and @ 14min 15sec!!!! Just last week I was at the 17 minute mark at this level!!!! Also I noticed when I hooked it up to the assist a quick message came up that it was an invalid DJI battery, but went away quickly and I have never got that before. All of this seem like an issue!!
     

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  14. ElGuano

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    Your discharged cell voltages look really good - 3.74 - 3.77 is very consistent between cells. Your ending voltage of 11.27v is also consistent with ~70-75% drain. It's indeed a bit high to be hitting auto-descend, hope you get it squared away with DJI!

    The battery notice isn't uncommon - it takes a split-second for the bus to authenticate the battery, which is enough for the "invalid battery" notice to pop up. But note that:
    1. The Phantom won't arm if the invalid battery notice maintains, so the fact that you can fly normally suggests this is no problem; and
    2. The Phantom will NOT auto-descend or take any adverse pilot action if it gets an invalid battery notice in the air. So this is likely not contributing to any issues you have.
     
  15. RoyVa

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    The battery is the issue. When it detects the voltage going to low it will autoland where ever it is and make no difference what's under it. I have 4 batteries and had one during flight returning home pop up on screen and tell me low battery auto landing. Lucky enough then"find my Phantom led me to it. Later that week in rotate my batteries and I used the same one. It said that it was fully charged and testing the cell had all four lights. The cells in the assistant were also showing good. Then during a flight I got the error again and I saw it drop power OSD from 65% to 8% in a split second and then the auto landing kicked in. Down she went in thick woods. Had some minor damage but could have been really bad. Charged that battery and went through the checks. Looked good. Tested in back yard flying low and it did it again ... Chucked that battery for disposal. End of problem. But presented another. When will it happen again with another battery?
     
  16. Timtro

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    Have you tried cycling the battery; that is running it down to under 18% and then fully recharging? I had one battery (my #5) that would fluctuate in flight and suddenly show warnings at 50%, but a hard discharge/recharge seems to have solved the problem. Something about balancing the cells. (P2H3/3D)
     
  17. RoyVa

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    Did that right before the last test. I cycle my batteries at 20 flights as DJI suggests. This particular battery show good and cells were balanced good but it would just drop charge. So I dropped it. It was at on its 45th flight.