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Phantom 3 Battery Characterization

Discussion in 'Pro/Adv Discussion' started by TheRealNick, Feb 2, 2016.

  1. TheRealNick

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    I put together the attached graphs and quick reference table to help everyone determine what a normal battery looks like over the course of a normal flight. The ambient air temperature was about 26.5 Celsius which is about 80 Fahrenheit. There are 4 flights shown in the graphs (2 different batteries with about 20 charges on each). The quick reference table could be printed and used as a way to check that the percentage lines up with the reported battery voltage. An important note is that the voltages are under flight. For example, if you power up and your battery is at 15.5 V before take off, you battery is likely much less than 80%. As soon as you liftoff you can expect a big voltage drop and then that is the voltage you would use in the table. So, if it was at 15.5 V before take off and then on takeoff it drops to 14.5 V you are likely at 30% or less and should land.

    To summarize the guidelines: when you power-up your voltage should be over 17 V, after you lift off it should be over 16 V, and you should land at 14.4 V (3.6 V) per cell. The battery will shutoff at 12 V (3 V per cell). For most people you can probably check the 17 V before takeoff and the 16 V right after you are in the air and then trust the DJI GO app, this is what I do. In my memory most crashes occur when the battery is around 15.5 V before takeoff and then quickly drops to 14 V once in the air, despite the DJI GO app showing a higher percentage....

    I do not recall multiple flights within a 6 hour window being an issue (I do not do this), but if it has been longer best to charge up!

    Enjoy!

    Thanks go to @BudWalker for his dat converter tool that made this possible...
     

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  2. Mark The Droner

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    Nice summary - thank-you
     
  3. TheRealNick

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    Anymore feedback?
     
  4. John Locke

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    It may be good to know that the motherboard firmware monitors the individual cell battery voltages. This monitoring triggers events based on the lowest cell voltage, not an average. If any of the 4 cells get to 3.0V, auto land or power shutdown will surely occur. So if you're at 3.6V in a hover, then give full throttle and 3 cells go down to 3.1V and one of them goes down to 3.0V, you're in grave danger, assuming you're still flying. At 3.6V you should NEVER give the bird full throttle to scramble back home in a panic, you should slowly make your way back to land, if it hasn't already enabled auto land. It's good practice to be within eyesight at 40% (3.65V), or start heading back to be within eyesight. Oh, I forgot, you're always suppose to be within eyesight. My bad.

    1.6 firmware has a governor in the s/w to prevent full throttle after 3.6V. This is to specifically prevent a power shut down event, however that doesn't mean power shutdown can't happen if you push things to the limit, although I've never heard it happening with 1.6 yet. I've never heard that DJI actually removed the power shutdown routine at low power. I wish they would implement a s/w routine the totally prevents power shutdown while flying. That seems so logical to me, I'm surprised this was not considered.
     
    #4 John Locke, Feb 3, 2016
    Last edited: Feb 3, 2016
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