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power module question

Discussion in 'Beginners Drone Forum' started by hellbilly75, Feb 14, 2016.

  1. hellbilly75

    hellbilly75 Member

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    Posted by hellbilly75, Feb 14, 2016 #1
    Ok, so I have an hk power module to provide voltage to a pixhawk. This thing has xt60 connectors and fairly small wire. My setup at 100% could pull 106 amps. I know I probably won't ever draw that much current but It's possible none the less. Could I make a heavier battery connection harness and also attach the power module to the pdb to utilize the reduced voltage for the pixhawk? I know the current info the pixhawk can read probably wouldn't work since the current wouldn't be passing through but would it still read voltage ok? Or am I way off base?
     
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  2. Posted by John Doecliff, Feb 15, 2016 #2
    I'm not exactly sure what you mean. Does it reduce the voltage down to a usable voltage so it will be a power supply for the pixhawk? If that's its only role then it should be fine as is, it will only see the current that the pixhawk uses not the entire current load. I feel like I need a better clarification, does it hook up in line with the battery and have the entire battery load pass through it? Because that doesn't sound right.
     
  3. hellbilly75

    hellbilly75 Member

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    Posted by hellbilly75, Feb 15, 2016 #3
    It is supposed to be between the battery and the pdb. But on my setup, I don't think it can take the current.
     
  4. Posted by John Doecliff, Feb 15, 2016 #4
    Ok so if it is in series between the battery and the PDB and everything must pass through it before going to the PDB then it sounds like a current sensor and not a BEC for the pixhawk.
     
  5. Hexacrafter

    Hexacrafter Manufacturer

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    Posted by Hexacrafter, Feb 15, 2016 #5
    From our understanding, it is both.
    There are several versions of PX4 power module on the market.
    Some like the HK version claim high voltage and amperage capabilities.
    The clients we have that are using PX4 on our larger aircraft have opted to not use this unit through the main power wires from the battery to power distribution as the concerns about the PCB boards limitations to amp draw. Either way, our aircraft all have redundant power to the Power Distribution in the form of duel battery leads - one pair directly from each battery to the power Bus Bars. This means that the power module would only be able to read the current draw from only one battery anyway.
    If you are using PX4 on a heavy lift aircraft with SERIOUS current draw spikes like a U7 series type motor, I would not recommend using this module on the incoming battery lead. This has always been a concern with the PX4 power module (BEC & Sensor board) in aircraft with high current draw. For us... even with our redundancy, with an expensive aircraft and payload... just too much riding on one little pcb....
     
  6. Paul-H

    Paul-H Member

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    Posted by Paul-H, Feb 16, 2016 #6
    Thats always the problem with these all in one solutions, one feature fails and you loose the lot. much better as said above to use separate systems and add backup systems to the critical systems just in case, as said above.

    Paul
     
  7. hellbilly75

    hellbilly75 Member

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    Posted by hellbilly75, Feb 16, 2016 #7
    Well, the plan is, going to make a main battery connection to the pdb with some 10 awg wire and xt90. Going to tap the power module to the board on one side for power for the pixhawk if it will work and use another 5 volt bec to the servo rail for backup. We'll see if it works.
     
  8. crayfellow

    crayfellow Member

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    Posted by crayfellow, Feb 17, 2016 #8
    The best power module available for Pixhawk/PX4/etc. is the MAUCH. It uses hall effect to sense current and there is a 200A variant for high-current systems. It is mentioned on the Ardupilot wiki as well. And the price is right. There's no reason to use anything else.

    The only downside is you may need to wait a bit. He's active on an rcgroups thread.

    Cheers!
     
    2 people like this.
  9. hellbilly75

    hellbilly75 Member

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    Posted by hellbilly75, Feb 20, 2016 #9
    Thanks Crayfellow. I looked at the Mauch. Definitely what I need. I went ahead and tried it the way I described above with the hk power module and it worked as I suspected. measures voltage fine, current measure is just what the electronics are drawing. Maiden flight was a success. 32 min in the air on a 4s 16000 mah battery and could have gone longer. end voltage per cell was 3.77. I'm happy.
     
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