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Loss of lift at 40% battery

Discussion in 'Phantom 2 Discussion' started by gavinski, Jan 3, 2015.

  1. gavinski

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    I typically bring my P2 in to land at around 30% of battery remaining just to be safe. The other day it started to lose vertical lift at around 35% just as I was bringing it in to land. Today it happened at 42%. The actual flight time was just over ten minutes with moderate flying. I have a go pro, mini IOSD, AVL58 on board.

    Is this a case of the data readout on the real battery level being incorrect? Or is something else going on?
     
  2. 4wd

    4wd

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    Sounds like the classic auto-descent from a failing battery, there was a great rash of this in the late summer July/August - then DJI have made some changes in the firmware which seems to hide or reduce the incidence.

    Updating everything if you haven't already - including the battery - is probably worth trying.
    Or maybe it really is going faulty. Depending how old it is and where you are you might get it replaced under warranty.
     
  3. jason

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    You haven't mentioned which software version you are using. In the latest update v3.08 there is a battery update v2.6 which will increase the battery flight time. I have had the same problem with two batteries that came with my P2 back last March and after updating both, which were auto landing at 40 - 45%, and testing both now auto landed at 7% that's a big improvement. Here's the video of one test flight.
    [youtube]https://www.youtube.com/watch?v=HjOZGMAfyG4[/youtube]
     
  4. gavinski

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    After swapping out the battery and updating the firmware I went for a test flight this morning and at 30% battery the P2 was holding steady. I will do another flight with the original battery to see if I can isolate the cause. But at least I don't have to worry about a premature landing for now.
     
  5. jason

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    Since you update the firmware did you also update your batteries? Both of my original batteries were under 30 charges when they began to auto land at 40 - 45% but once I updated both of them the problem was gone as you can see in the video. One thing I have noticed is my original batteries have round info pins and all three of my new ones are square.

    • P2, H3-2D, GoPro Hero 3+B, AVL-58, 5.8G clover-leaf antennas, iOSD-mini, Black Pearl 7" diversity receiver/monitor
     
  6. catware

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    I had the same issue last week, with a battery having only 27 charge cycles on it. I have Lightbridge installed so I commonly fly a kilometer or two away from base. At the end of a flight I returned to base with about 30% left and was doing some maneuvers right in front of me, when at around 25% the Lightbridge audible battery warning started going off and the battery % remaining dropped at about 3% per second. I was able to land okay before it reached zero.

    Thinking the battery needed to be recalibrated with its once every 20 cycles full discharge, I turned it on repeatedly and hand held it until the battery was fully exhausted and it wouldn't power up any more. I then did a full charge cycle on it, per DJI's recommendation. The battery only made it to three bars before the charge cycle turned off by itself. I unplugged it, plugged it back in, and then it charged back all the way up.

    A few days later I took off for the next flight, and flew a couple hundred meters away. The battery was at ~85% when the battery alert sounded again, and just like before the % remaining began dropping at about 3% per second. I was able to fly back to base as fast as possible and land with less than 20% left.

    This battery is less than 3 months old, and I contacted the retailer and they are replacing it under warranty. Very scary if this happens again when I am too far out to return to base.
     
  7. Zinnware

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    You need to look at the voltage level too not just the % battery level. In the manual it states the following in the "Low Battery Capacity Warning Function" section:
    "There is a hidden third low battery threshold in addition to the 1st and 2nd level warnings. This uses 10.65V
    as its threshold. Both this voltage threshold and the 2nd Level Low Battery Warning will trigger auto-landing.
    Altitude can be maintained if necessary by pushing up on the throttle stick."

    Your battery may be experiencing low voltage levels despite the % remaining. I have seen this happen under full throttle maneuvers.