12v Car Battery Tethered F450

I'm not new to RC but still learning electronics, can anyone think of a reason why I can't tether a DJI F450 to a heavy duty car battery for an exhibition?With 4x20A esc,s it doesn't seem like that would draw too much power. Obviously would need to rest the motors.I can't find any examples of this on YouTube which makes me think it might not work!Interested in your thoughts?

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  • Why deep charge cycle?
  • Ed, excellent work with your tether project. I'm an engineer with the Maryland Test Site / Aero Dept. Can you share some part numbers and specs for the transformer (or perhaps transformer rectifier) you used on board? Also the part number or precise spec of the cabling? I have a project with a requirement for persistent flight and I need to build a tether similar to yours. Mine will be for a 3dr Solo, and if my project comes to fruition I will be happy to make the build public for everyone's benefit. 


    Ed Elias said:

    You could, we've done this. http://diydrones.com/forum/topics/successful-tethered-flight

    The problem you have is the F450 probably needs 12 or 15V (3S or 4S) and so if you run that down a cable you'll get a very large voltage drop over the length of cable. To prevent this problem, you have to make the cable thicker but this adds weight. The alternative as iskess says is run higher voltages but you'll then need onboard electronics to step it down to the 12/15V the motors need.

    How far/high are you hoping to fly?

    The second issue (perhaps a minor one in the scheme of things) is that the car battery needs to be a deep charge cycle battery as normal ones are not designed for this kind of application.

    Hope this helps, let me know how you get on.

  • The finer the strands in the wire and number of them lowers the voltage and amp drop over the distance .Basic DC  welding knowledge .....The current travels along the surface of the strands ,not through the core of the wire ,so an extra fine stranded high count strand cable is what you need .

    Try "pumping" 48V DC down 1500 feet  underwater  ,that is a 3000 foot loop  so oh yes we had to crank the amps up to be able to work  in wet or dry habitat welding .

  • SkySapience Tethered Drone

    Your idea is already a reality in the form of a tethered drone that was

    developed by an Israeli firm a couple years ago.  Designed so it can

    be transported by a ground support vehicle, the drone carries a camera

    and other sensors which feed its view back to ground operators. 

  • You could, we've done this. http://diydrones.com/forum/topics/successful-tethered-flight

    The problem you have is the F450 probably needs 12 or 15V (3S or 4S) and so if you run that down a cable you'll get a very large voltage drop over the length of cable. To prevent this problem, you have to make the cable thicker but this adds weight. The alternative as iskess says is run higher voltages but you'll then need onboard electronics to step it down to the 12/15V the motors need.

    How far/high are you hoping to fly?

    The second issue (perhaps a minor one in the scheme of things) is that the car battery needs to be a deep charge cycle battery as normal ones are not designed for this kind of application.

    Hope this helps, let me know how you get on.

  • You need to do some basic math. First, how many amps does the quad pull at max throttle.
    Then google a chart on wire gauge (AWG) and see how thick your wires must be for the height you want to fly. Then find out how heavy that much wire is.
    You will find that the wire is very heavy. You can either fly quite low, or use much thinner wire. To use thinner wire you need lower currrent. To get the same power with low amps, you need more voltage. Most people who have attempted this successfully are using 120v up to the copter with an onboard voltage regulator to lower to voltage. But these are also heavy.
    If you don't need to fly high, it could work as you described.
    Make a spreadsheet and tell us how high you will get and which wire gauge you will use.
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