Hi @Rov36,
No - if anything they’re generally more efficient than equivalent brushed motors, because they don’t have friction from the brush. That comes with reduced wear and longer lifetimes, at the cost of a motor that’s harder to manufacture (so more expensive) and more complex to control.
If you’re interested in a bit more detail, this article was one of the first results from a search of “efficiency of brushless vs brushed motors”.
A thruster produces a pressure differential. How fast water flows through it depends on
- the rotation rate the motor controller is aiming for
- other forces on the system (e.g. from water currents, and other thrusters)
How fast the thruster itself ends up moving depends on
- the water flow rate through the thruster
- the weight and drag characteristics of what the thruster is attached to
- the orientation of the thruster relative to the existing system motion and its lower drag directions
Our thruster product pages (T200, T500) include a Technical Details section, where you’ll find current draw maxima and a variety of plots, including a plot of power usage vs (static) thrust. There’s some discussion of thrust at speed in this thread.
Our Lithium-ion battery is rated to 60A continuous output, subject to temperature constraints. Cool water and a metal enclosure can help with keeping the battery cool enough.
Current usage depends on how hard the motors are being driven. Runtime depends on battery capacity and current usage. For example, if your vehicle usage is mostly extended periods of high throttle then that’s not how an ROV is generally expected to be operated, so you’ll need to determine/measure your own runtime estimates rather than using the ones in our BlueROV2 technical details.