Help with wiring Raspberry pi + Pixhawk + 6/8 ESCs

Hello, I want to power my ROV; It has 6 T200 thrusters. As I saw in the Technical details of the T200 thruster it says that it needs 32 Amps to work on full power.
I want to make the electronic structure able to support full thrust.
I am searching online, but I coluldn’t find something that clarify the topic to me.
I have a 22.2 V 6s Lipo battery.
Assuming that I am using this PDB(power distribution board )

which will be connected in the following manner. How would I be able to power the Raspberry pi?
I am aware that using the Fathoom-x converter for the tether may convey power, but I am not sure from how effective it is, so I believe that powering the Rasbbery from the battery is a assuring idea.

What are your thoughts?

Hi @AthunestMB, welcome to the forum :slight_smile:

Please be aware that the maximum specified operating voltage for our T200 Thruster is 20 V, per the technical details, and a 6S LiPo battery is outside that range. You can check this comment for some extra context.

There are a few different things you could mean by this, which have varying design requirements:

  1. You want to support running all thrusters at full throttle for extended periods (e.g. diagonally downwards)
    • This can be challenging/expensive, and is not how ROVs are typically operated
    • Your battery and PDB would need to handle 6x36 = 216A of continuous current from all the thrusters simultaneously running at full throttle, which is well beyond the 60A rating of your PDB, and possibly outside what your battery can handle as well
  2. You want to support occasionally running some thrusters at full throttle for brief periods
    • This is reasonably typical for exploratory ROV operation, but is not appropriate for high speed long distance travel
    • If you have 4 horizontally oriented thrusters, and 2 vertically oriented thrusters (like on the standard BlueROV2) then to be able to run full throttle
      • vertically you’ll need a battery and PDB capable of handling 2x32 = 64 A of burst current
      • horizontally you’ll need 4x32 = 128 A of burst current capacity
  3. You want something in between
    • What kind of performance you need is up to you, with the corresponding costs
    • You may need to employ one or more of these mitigation strategies, to avoid under-powering your control electronics and losing communication with / control over your vehicle

Note that the ESCs also need to be able to handle your desired current. For reference, our Basic ESC is only rated to continuously supply 30A, and that’s with cooling measures in place to stop it from overheating.

Ideally you would have a completely isolated power supply for it, but that’s generally annoying enough to manage that it’s more common to use a 5V voltage regulator that can draw power from the main battery.

That does come with the added risk of excess current draw restarting your electronics though, which it’s advisable to mitigate automatically (in software configuration) rather than attempting to avoid pushing too far on a joystick.

Do you have a link to that software configuration process? I believe we are having a similar problem and are limited to 25 A max per MATE competition rules.

Hi @Thanatox -
You can try using the MOT_BAT_CURR_MAX parameter, adjustable from the Autopilot Parameters menu in BlueOS.
This will have some delay in response inherently, you could also try reducing the max PWM frequencies allowed, again editing relevant parameters in the same menu.

Thanks Tony.
Reducing the Max PWM frequencies solved our problem!

That parameter was buried deep. It might be worth a mention in the setup and or troubleshooting instructions for the Navigator board.

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