Cooling the ESC


I think using the forward motion of the foil to ram water through the tube is attractive for it’s simplicity but I worry about debris clogging the tube causing the ESC to be damaged from overheating. Having the waste water vent out in a highly visible location is a great common sense sanity check that cooling water is flowing as expected.

Another approach might be a closed loop cooling system using the hollow metal foil mast as both a heat sink and coolant reservoir of clean water. Might help keep the wires cooler too.


Which pumps are people using for water cooling the ESC?


Dumb questions:

  1. why don’t you put the ESC inside of the mast or propulsion casing so that it can dump heat into the water via the conductivity of the surrounding aluminum?
  2. Does the battery unit itself need active cooling? (On ebikes they are often air cooled)


There isn’t a lot of room inside the mast for the esc. Not sure about the batteries, it probably depends on which batteries you have.


What do you all think of these aluminum enclosures? I think they will do better with the heat than the poly carbonate boxes. IP67 waterproof, is that enough?


We are using our jet nozzle as the has incredibly high flow, and runs more water as you use more mower self regulating cooling demand. A 90 brass elbow Tapped into nozzle and waterline up the inside of mast. We did this with our ducted propeller setup last fall as well and it also worked well.

Can you recommend an ESC?

Is closed cooling esc system smart? It would remove need of washing the tube after each use (salt, dirt, seaweed). Could aluminum mast be a good heatsink? Silicon tubes would go from esc through the whole mast and back, with some anticorossive coolant or whatever?


I use a closed system. A plexitank 900ml heats up from 20 to 45 C in a session semms to work fine.


Is it so difficult to dissipate the heat? The ESC is used underwater, we should use water to dissipate it, I’m considering to add 2 pipes in the ESC heat sinks , the pipes will be full with water. I’m going to share you my pictures after I finished it.


Other than aditional weight, i see no drawbacks. U use pure water or some other liquid? I am guessing only Hiorth brotherz need some antifriz. :wink: Hope your knee getting well!


Just water and I suppose I can go down on the water volume too.


Most ESCs have finned heatsink (like the 180 amp turnigy I am using). Doesn’t placing the ESC in an enclosure prevent air from flowing across the heat fins? Has anyone tried keeping the fins exposed to air to help with cooling? Or possibly a small computer fan placed in an enclosure (means the enclosure wouldn’t be completely sealed)? I’m thinking of keeping the heat sink fins exposed to air by cutting an opening in the top of the enclosure for the fins to stick out and then sealing around it. Also will use the water cooling in addition. Thoughts???


they have done it - and but the ecs right under the mast - quite cool :wink:


The air flow would have to be massive. Look at the size of a passive CPU cooler. They are huge and maybe only use 200W.


Flying rodeo has big metal sheet on the bottom of his board. I think he is full pasive without water cooling.


I was rather thinking about diffusing compressed air only or a mist of fresh water (nebulization) following this example:
Thierry Monnot The Breizh Maker method. . Here are the pros and cons I see:


  • low water consumption - should represent a small syringe/tank of 100ml (cc) (3.28 US fl.oz) per hour
  • dissipates a lot of heat. To be convinced, just look at videos where they mill aluminium at high speed. It is amazing how a few drops of water mist make a difference at tool level.
  • easy to Diy using a 12V fish tank air pump and airbrush technology
  • cheap technology if you don’t DiY your head (10USD on Amazon, ebay or Harbor Freight), 0.2 / 0.4 or 0.8mm nozzle still to be defined according to heat to be dissipated


  • you need 650 L/hour of air for the air compressor (actually a fish tank water pump) whist you are trying to prevent sea water to get in…
  • it’s not a carefree solution as you have to fill or at least check your small water tank level before riding your board
  • ESC surface might slightly oxidize (not sure at all though)
  • the ESC must be set in a separate box
  • might be difficult to prime or tune… simplification ideas will be proposed by the eFoil community :sunglasses:
  • you reintroduce humidity in a case where you didn’t want it to be initially (electrical risk ?)
  • more to be defined …



I am thinking of running a small closed loop of some copper tubing down the mast, filled with simple car engine coolant. I would try to keep the volume as low as possible. Apart from the time it takes to heat up several hundred ml of coolant, copper has high thermal conductivity and should dissipate quite some heat inside the mast. What do you think?


Why not just water? Cars only use special coolant for the winter, so nothing fezzes. But if you don’t leave your board outside in the winter, you wont need that (and if you do, you can simply empty the system).
What if your system leaks? You don’t want to pollute the lake you are riding at!?


I just see that Takuma and/or their partner BBtalkin claim a patent-pending on cooling for their e-takuma. This type of cooling has been public knowledge for a long time, at least since I published it October 5th 2017 here. It has been discussed on this forum many times after that. Unless they filed before it became public info, it should not be issued.


These coolants also have anti corrosion additives, but water will work fine I guess.