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Discharge rate with motors off? Or how keep IMU warm?

Discussion in 'Phantom 1 Discussion' started by Videoguy, Sep 13, 2014.

  1. Videoguy

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    Hi, does anyone know the discharge rate or amount while just letting the P1 sit, without motors running? I'm a pro video Director, and I'm going on a Shoot in a week, of whitewater kayakers coming down a river. The challenge is, from the time I see them coming around the bend, I probably only have about 10-20 seconds to get airborne and line up for the shot. So I need to figure out how long can I sit, while waiting for the Shot. I'll do some tests, seeing how much voltage drops at various time periods, I guess. But it would be better if I could be more precise, somehow.

    Or, if anyone has a better idea, I'd sure appreciate it. Ideally I'd use a spare battery to keep the IMU warm, then just disconnect and plug in the onboard battery. But I can't get that to work properly. I tried plugging a spare battery into the Phantom, and waiting for a few minutes, well after it's take-off ready. Then I disconnect the spare, and quickly plug in the onboard battery. At that point I get alternating green/red flashes for about 3 or 4 sequences, then a sequence of 3 green flashes, and those 3 greens repeat indefinitely. I haven't tried flying at that point, I'm too worried about a fly-away, especially since my shoot is in a week. And after poring over the LED codes, I can't find anything that matches those sequences.

    If I wait about 1 minute after disconnecting the spare, and connect the onboard battery, It's ready to go in about another 45 seconds. So that's 1:45 total ... way too long.

    FYI I'm using a 3300mah battery and a Sony Rx-100, so I normally get just about 7-8 minutes of flight time (but the Sony makes it worth it!!!) I know, I'm beyond the specified payload, but it actually gives me some amazing, very professional results.

    Any ideas would be appreciated!
     
  2. OI Photography

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    When sitting with the motors idling (right after you start them), it draws a total of about 2.1A. Before starting them it's around 1A. As soon as you increase thrust enough to get airborne it jumps to at least 16A, probably more like 20A with your total weight. Average draw while flying 1350g is about 23A.

    I don't know if that will help you do the math you need, but my rough estimate is that every 10 minutes you sit on the pad powered up without the motors started will eat a little over 1 min of flight time.

    Thinking about your situation, I'm wondering if it might be easier to position a helper further up the river with a walkie-talkie, who can alert you to the approaching kayakers earlier to give you more lead time...?

    Note: the current draw figures I mentioned include an H3-3D and 600mW FPV transmitter.
     
  3. Videoguy

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    Thanks, that's very helpful. And yes, I've thought about positioning a helper, and will try to do that. I just don't know if he can get access to the river or an overlook, with enough lead time. Good info... thanks!