I am building a bathymetric pontoon boat that weighs 34 lbs. I have 2 T200 trusters and 2 - 20 V 5A batteries that I have efficiently dropped to 12 V using a 95% transfer efficient dc to dc step down regulator to drive the motors. I only plan on going 1 to 2 m/s. The question I have am I better to use the 20V and less throttle or 12 V and a little more throttle to achieve maximum distance at a given thrust. I have looked at the motor efficiency and they seem the like the lower voltages better.
Hi @Cobra1502 -
The biggest hit to your efficiency will come from the T200 nozzle, vs. using a M200 with weedless prop like the BlueBoat employs. Nozzles on thrusters provide higher bollard (static) thrust, which is good for applications like an ROV where you often want to push hard, and not move very fast - however they are not hydrodynamic as you get going fast through the water, and will greatly increase the power required to achieve 1 to 2 m/s on a boat style vehicle…
Brushless DC motors are indeed slightly more efficient at lower voltages, as for the same power level more current is flowing, thus creating a stronger magnetic field to drive the commutation. However, the lower voltage does limit the maximum power achievable! A standard 4S battery voltage, 13-16.8V is a good compromise…
Can I convert the T200 over to a M200 or are these different motors and mounts. I do see the M200 is connected to the hull of the Blueboat using a rear mount on the M200.
How much more efficient is the M200 with weedless prop as compared to T200?
Hi @Cobra1502 -
The T200 is fundamentally different, you could cut the 4 arms that hold the nozzle off, and remove the nose-cone for mounting. The weedless prop would only work with the nozzle out of the way, it is a larger diameter. The M200 has better mount points (as the holes on the back of the T200 motor are intended for the nose-cone only), so I’d be wary of running a converted T200 at full power in reverse…
I would guess your vessel would be at least twice as efficient, but that’s a very gut-feeling estimate… Blue Robotics has not conducted extensive testing on this, and it likely varies significantly with overall vehicle drag. Doing a comparison, before and after thruster modification of watts consumed at varying speeds would be very interesting, and the only way to really know for sure!