Direct drive outrunner with direct water cooling


I use the calculator :
12s 80a should be around 40w… I guess it depends how is built the esc

My set up works with this:

But i am testing a watercooling Plate 50x80mm with a peltier module 75w and results are amazing!


For your heatsink this calculator estimates around 60 watts minimum to be able to dissipate for 2.5 m/s airflow (I used 150 as volumetric thermal resistance, whis is the highest value for 2.5 m/s [higher = less airflow, lower = more airflow], so there is much more potential). 2.5 m/s is only 9 km/h, that is reached quickly when trying to get on the foil.


The problem is there are additional losses in every cable, the PCB, the capacitors, the processor, interface, gate driver, plugs, fuse, BMS shunt, battery etc. There are hundred of watts loss inside the box if you draw 4kW. Most of these losses happen with low power density, e.g cables and plugs. Some with high; fuse, shunt and fets. With a heat sink you can cool the specific components attached to it and of course you lower the heat for the interiour of the box and thereby the average temperature by conducting some heat directly to the outside. To avoid lots of heat transfer to the inside of the box, the cooler needs to stay cool. Therefore the water contact which gives 10-100 times more W/m^2K.
Anyhow the remaining sources of power loss need to be cooled, i think i will still use my internal vent to withstand local overheating. Thats also battery friendly as the temperature is equalled better.


Ok, I see what you mean. Cooling the heatsink with water is nice of course, I also love the heatsink on the bottom idea, but the foil is a bit in the way. On the top it is hard to have water exchange.
I think it helps to separate batteries and ESC, so the top 2 heatsources don’t interfere. Then the batteries will be ok in a plastic box with some space. And the ESC will be ok with the heatsink (air cooling) and some additional heat dissipation through the walls of it’s aluminum box it is put into.
Edit: I will try it the way I described it here this winter and see if this solution has enough thermal budget for use in the summer, otherwise I will re-engineer it until then.


It would heat your toes! Thats the point! You stand on the ESC cooler and cool it by your wet feets!

What is your experience with the ARC200 ?


Ok, that could be comfortable :smiley:

To this point, unfortunately, only that it is pretty expensive with shipping, taxes and customs duties (import to Germany). I haven’t bought it yet as I wanted to know first how much I actually have to pay on top of the 299$. Also my build is progressing slowly anyway as I am busy at the university.
But I will order the Arc soon, I don’t see many alternatives of similar quality, the VESC 6 is too weak and the VESC 75/300 is waaay too pricey…


@Jezza what about you? Any experience with the ARC200? Too many cables?


I haven’t received the test unit yet. Freefly were waiting for adaptor cables. Once I have it and test it I’ll be sure to let everyone know though.