# Maximum length of Thruster Cable

We are building our second ROV with products from BlueRobotics:

T200
a) What is the maximum length of Thruster Cable that might work?
b) What is the maximum length of Thruster Cable that you know will work?

We have about 10-12 meters of needed distance, which is best:
c) ESC close to the motors (will need enclosure)?
d) ESC somewhere in the middle (will need enclosure)?
e) ESC cose to the battery (no need of enclosure)?

Light
d) How about Lumen Subsea, will they work fine 10-12 meters away from the controller unit?

Hi @ecofang,

That is not a question that can be answered simply or has a hard cutoff. Its a sliding scale depending on how much loss in thrust/efficiency you are personally willing to accept, and how large or a wire gauge you can use in your application.

As you extend the cable, resistance goes up, and voltage will drop along the length leading to energy loss in the form of heat, and reduced thruster performance due to the lower driving voltage. You can offset this by using a larger wire gauge with more copper/lower resistance.

I suggest you run some numbers through a voltage drop calculator and take a look at the T200 performance charts to come to your own conclusion. Our own voltage drop calculator should be helpful:

If you extend the cable length between the ESC and thruster, is it critical to make sure the resistance along all three phase wires is the same, otherwise the thruster will not operate properly.

If you extend the cable length between the power supply and ESC, make sure the voltage drop under load wonâ€™t result in less than the minimum voltage (7 V for our Basic ESC) being delivered to the ESC. Otherwise, it will not be able to operate and will shut off under load.

The situation is similar for the Lumen light. However, since the Lumen has an extended operating voltage, you can also increase the voltage of your power supply to be able to get away with a longer/thinner cable due to the reduced current draw. It depends purely on your driving voltage and the cable gauge.

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HI @ecofang,

When using the voltage drop calculator for the AWG, what is the number of conductors:

Between the ESC and motors, is that:
a) single set of conductors
b) 3 conductors per phase in parallel (will the calculated value be for each wire or for 3 in total)

Between the battery and ESC, is that:
c) single set of conductors
d) 2 conductors per phase in parallel (will the calculated value be for each wire or for 2 in total)

Or is it some of the other choices there - I became confused in this issue and about phases, please explain? To put it simple, I just want to calculate the AWG for each individual conductor.

Hi @ecofang,

It is only a single set of conductors for both. A compete circuit (power and ground) is assumed by the one way distance to load input in the calculator. For the thruster wires, at any given moment current is only flowing through a single pair of conductors in alternating sequence.