Mounting ESC in the water


#1

Hello everyone! I am new to ROV's, but I have a good background in electronics and aircraft. Being new, I have some questions that might seem odd. I'd like to learn as much as I can from this community and make a proper ROV for deep dives.

I'd like to build an ROV that uses BLDC motors and hobby ESC's so I can control them with the same PWM as model aircraft. But, it seems to me that using a more powerful ESC, or using more ESC's inside my waterproof chassis might result in overheating or turning the tube into an oven. Is this a real danger underwater, or is the thermal conductivity of the water so great that there isn't a problem inside the tube?

Is it a dumb/bad idea to mount the ESC in the water, assuming it is potted correctly? Is there such a potted ESC?


#2

Hey Nicholas,

Your concerns about thermal issues a certainly valid.

Potting the ESCs and putting them out in the water is a very interesting idea, but keep in mind that too much potting may actually insulate the ESCs and cause them to overheat.

We’ve noticed that with three ESCs in our acrylic tube, it can get pretty tostey inside, but if we could create a good thermal path between the ESCs and the water (such as a hunk of aluminium that protrudes through the endcap) I’ll bet things would be a lot cooler.

Please post what you come up with!

Eric


#3

water and electronics is never a good idea.

there are thermal conductive epoxy available, but its hard to get this potting completely watertight, the epoxy bond diffrently to varius components and shrink during potting, and thus making microscopic cracks betwen components and the mould.

a solution could be to have round bars of aluminium or copper connected to the heatsink or the FET transistors underneath the heatsink, and transfer this to the outside of the electronics container trough the endlid so the heat could be passed to the water.

of course a aluminium endlid on one side of the electronics tube with the ESC's connected to would be really good solution.


#4

Heat is a real issue. The only source for potted ESC's is from Crust Crawler but they're pretty pricey. You could pot your own, but I'm with Thomas, exposing your electronics to water can be iffy at best. Another option, and one I used, was to use some tiny 12v muffin fans to move the hot air around the vessel. My watertight container was made out of aluminum, which probably helped some as well.


#5

Blue robotics sells a potted 30a ESC that has pwm or i2c options… Less expensive than other alternatives I’d wager.