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T200 thrusters only pulling 1-2 amps

When running my T200 thrusters, they only seem to be pulling 1-2 amps even at full throttle.

The thrusters are at the end of a 40ft 18 gauge stranded wire (tether) running at 12V DC.

At the other end of the tether is a Blue Robotics Basic ESC hooked up to this power supply and run off an Arduino Mega.

The Arduino code is this (if that makes a difference):

servo.writeMicroseconds((msg[4]*400/127)+1500);

Where msg[4] is between -127 and 127.

Any assistance is appreciated! I’d be happy to provide more information and test things on my end

Thanks,
-Zman

Hi @Zman350x,

An 18 AWG cable of that length will have excessive voltage drop under load, there’s likely only a few volts actually making to the thruster, resulting in the much lower current draw and thrust output.

You can use our voltage drop calculator to get a better idea of what is going on and choose an appropriate wire size.

In general, we recommend keeping the ESC within 1-2 m of the thruster, and extending the ESC power lines if necessary. Excessively long thruster wires can interfere with the back EMF sensing of the ESC and proper commutation of the motor.

It sounds like you may be building a competition ROV, perhaps for the MATE competition- we have a guide with some suggestions and general tips for using our component in this application, you may find the section discussing surface power and tether sizes helpful.

-Adam

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