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HOW TO: Monitor battery voltage to watch for signs of failure

Discussion in 'Pro/Adv Discussion' started by msinger, May 27, 2015.

  1. msinger

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    It's important to monitor the battery voltage in each cell of the DJI smart battery. Be aware of the following:

    1) Monitor the battery to ensure all cells maintain a similar voltage.
    2) Do not allow any of the battery cells to drop below 3.3V.
    3) Consider landing your Phantom when (or before) the first battery cell reaches 3.4V.
    4) Your battery will shut off mid-flight if the voltage drops below 3.0V.

    You can display the voltage of the lowest battery cell on the main screen of the DJI GO application. To do so, enable the "Show Voltage On Main Screen" setting in the "Aircraft Battery" --> "Advanced Settings" section of the DJI GO settings.

    ShowVoltage.png


    Once enabled, the lowest battery cell voltage will appear at the top, right of the DJI GO application -- like this:

    VoltageMainScreen.PNG


    In the "Remote Controller Settings" section of the DJI GO settings, you can set either C1 or C2 to "Battery Info" to quickly open/close the battery settings.

    C2.PNG


    Below is an example that shows a battery that has a consistent voltage in each battery cell.

    Cells.PNG


    And, here's an example that shows a damaged battery:

    BadBattery.png


    It's important to ensure your battery is in good health prior to takeoff. Flying with a battery that has one or more bad cells could cause the battery to discharge very quickly and/or your Phantom to shut off mid-flight and drop from the sky.
     
    #1 msinger, May 27, 2015
    Last edited: Nov 8, 2016
    Ryan Haber, NRJ, TheSnowman and 54 others like this.
  2. jlo

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    Nice informative post. Thank you.
     
    omarkatwe likes this.
  3. zincsoldier

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    Thank you for sharing!
     
  4. fhagan02

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    GREAT information. Thanks for sharing this.
     
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  5. bobmyers

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    Great info!-- :)that critical low cell is the killer--- :eek:
     
  6. NoOne

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    Is this battery starting to go? The lowest cell is showing a .03-.05 voltage difference from the others. When is it time to toss the battery? When it's < 90% Battery Life? Please note that the 23 charges shown are not full charges. Sometimes I top it off before I use it if it has been a few days. Is that bad?
     

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  7. bobmyers

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    This is not an abnormal variance, I would become concerned if one cell is .1 lower than the other cells and it did not equalize closer with fresh charge. If it is lower and never recovers closer with a charge, they it might be time to pull it.
     
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  8. bobmyers

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    You should always start with a fresh battery if possible, or stay close.
     
  9. NoOne

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    I actually had just finished running it for about 3 minutes before I took the screenshot.
     
  10. bobmyers

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    The important thing to remember is to monitor the battery a few times during the flight -- set up one of the switches on the bottom of the controller to bring up that screen so you can look at the cell status a couple of times during the flight-- also have the battery condition turned on the top of the main screen. if you have one low cell, flight time will decrease rapidly and the Phantom may land rapidly if power starts dropping.
     
  11. mrburris

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    Thanks. Much appreciated.
     
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  12. Andrea

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    Thanks. Good lesson.
     
  13. allemtura

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    Thanks! What battery percentage equates to 3.3v out of interest? Why is it bad to drop below 3.3v?
     
  14. bobmyers

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    A lipo cell may go be damaged anytime a cell voltage drops below 3.6-3.7. A cell at 3.3 is pretty much toast and probably wont ever recover.
     
  15. NoOne

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    At what Battery Life would you toss the battery? I saw that cool deaf dude on YouTube mention that below 90 they should be tossed.
     
  16. bobmyers

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    For sure-- the cells will probably be totally out of wack and have too much variation.
     
  17. silverstoned83

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    If you're talking about resting voltage, then 3.3v would be 0%. In fact, you've probably entered the batteries tiny amount of reserve capacity, which should not be done without expecting damage to the capacity/lifespan of the LiPo. A good rule of thumb is to consider 3.85v as 50% capacity remaining and around 3.65v to be 0%. The cell voltage under load will be even lower when flying, probably closer to 3.4v/cell. I'm still in the break in process for my batteries, so I have yet to test this.

    One thing to note is that these batteries use the newest LiPo tech call LiPoHV which uses a chemistry that's capable of a slightly higher voltage when fully charged. Considering that this is still a relatively new LiPo chemistry, I'm not sure if the same rules apply from the older LiPo chemistry or not. Perhaps someone from DJI could chime in on this. I'm also curious if the "80% rule" should will be followed.. Which basically just means that you should never consume more than 80% of a LiPo in order to preserve its health. If this is still the case with the LiPoHV chemistry, I would like to know if the battery percentage estimation on the Pilot App takes this into account. If it does, then 0% should still be leaving around 20% to preserve the health of the battery. If anyone can clarify this for me, I would much appreciate it.
     
  18. silverstoned83

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    In my opinion, I believe with enough care, you can expect well over 100 cycles. This means never leaving the battery fully charged for more than a day or two, never over discharge the battery, no exposure to excessively hot temperatures, etc.

    As long as you take care of the cells, they will stay balanced over the lifespan of the LiPo, and only lose capacity over time. I would replace the pack once it loses around 20% of its original capacity, or when the cells start to become more out of balance after a flight.
     
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  19. tvckz

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    Txs
     
  20. NoOne

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    What about time to discharge? Should that be set to 10 or 7 days? Does it matter?