Help building my first multi-copter

Hi all,
Im a newbie and building my first hexacopter to take ariel photographs. I have done a lot of research but I am struggling to understand if I need to use a UBEC on my set up.
I am running an Arducopter APM2.8 and wanted to use the 3DR Power Module plugged into the board using the PM slot. It will be connected to a 4S battery to start with but want to upgrade to a 6S battery in a few weeks once I connect my camera equipment (want to learn to fly first).
I am using OPTO ESC from AFRO, missing the positive wire to the board (this is how they came).
My question is with the power connected, do I still need to use a UBEC and if so what is it doing as I believe the power module powers the board etc and the ESCs get power straight from the battery. Am I right? 
Also, if I am right and don’t need a UBEC, does jumper 1 need to be installed?
Finally, will this set up work with both the 4S and the 6S batteries or will leach require a different set up?
Sorry if these are simple questions, but struggling to find the answers, or at least in a form I can understand.
Thanks in advance.

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  • No worries John. Sometimes it's nice to have things written in plain English, especially when you're new to something and still learning the basics.
  • Hi, I am very new on multi-copter. This thread really help.

    Thank for your question Chris !

  • Hehe, yea that's always tricky... I'm not sure what kind of Frame you have, but I usually tie string (maybe fishing line) to a nut, and then put the nut through, so that you have a string that goes through the whole tube. Then tie the servo cable to the string and pull it through.

  • Thanks Kyle. Im using Tarot 4114 320kv motors which I believe are 6s rated.

    Im looking forward to getting it airborne to be honest and learning to fly.

    I do have another question. I've managed to thread the positive and negative leads through the carbon tubes from the ESC's to the PDB, but now I can't thread the servo cable through, its getting stuck on the end and won't go past the screw,

    Is there a trick or tip to get it through or is it a case it just won't go?

    Kyle - CrimsonUAV said:

    Also make sure your motors are 6s rated :D, but sounds like you know what you're doing!

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  • Also make sure your motors are 6s rated :D, but sounds like you know what you're doing!

  • Thanks all, this is really useful information. As I am using a 4s battery to start with and then swapping it to a 6s do I need to do any re configuring or just swap the power module for the one mentioned or use a ubec?

    So a simple swap.
  • HobbyKing sells a similar power module, rated to 10S and 2.5A.

  • Hi Chris,

    Basically, this information is available on the Ardupilot Wiki and at



    It is possible to use the power module by itself without an additional UBEC or ESC with a built in BEC so long as you are only powering ESCs from the power module.

    If you are using Servos or brushless gimbals you really need to have a BEC or UBEC as well because the 3DR power module is only rated to drive the. Pixhawk load.

    The ESCs themselves are provided with power from the battery and the speed control lines from the Pixhawk only control signals and do not represent a significant load.

    For use of ESCs only and using the power module only you do not need the jumper.

    And as Mike says you can only use the 3DR power module for up to 4S, If you go to 6S you will have to remove the 3DR power module and substitute an appropriately rated UBEC.

    Best Regards,


  • First up, if you are going to 6S then the 3DR power module won't do it, they are rated to only 4S.

    Unless you are driving servos from the output rail you won't need a BEC. The power module is rated to 500mA.

    When you go to 6S after setting up with 4S the parameters will need adjustment due to the higher rpm and responsiveness of the motors.

    You should not need the jumper on as the output is not using power.

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