I would rather make the single components waterproof. So they can still be disassembled from the box.
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mmm two waterproof potted battery connected in series
How about a 3D printed battery pack case/sleeve that is brushed with epoxy?
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What about putting 2 tubes with a screw lid for the batterie in the two spaces, accessible from the back. Cable to connect inside.
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Just in case anyone is interested, and I’m happy to share files.
I found that the 100A Maytech ESC would overheat too quickly, even when only using 40A to start and 20A to cruise. So, I added water cooling and decided to route the cables through an Axis mast. This was fairly easy to do and I would recommend it if you’re into efoiling.
It’s amazing how cheap and easy it is to build these setups, although in this case, I’m running 12S. I now have two setups: one using 2 x 6S lipos and a 100A Maytech ESC, and another with a cheap 6S ESC. Axis masts are affordable enough to have a dedicated efoil setup.
Unfortunately, I don’t seem to have photos from when I drilled out this mast. I’ve seen people literally cut out the back of the mast; however, this weakens it significantly. It’s much better to drill through the side.
You can see my massive heatsink in one of the photos 
. I have a much smaller heatsink to replace it with now, but I just haven’t gotten around to it as I don’t really use the efoil. A water cooling block in place of the heatsink would be a better solution now. No pump required for the watercooling. There’s enough pressure from around 6kmph.
There’s a lot that could be easily improved but this was very quick and easy to build. Could easily make another in half a day.
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Great idea, is the water cooling just one way to the external heatsink and let water go on it? If you have the stls for the mast clamp that would be great!! thanks!
Yea it just squirts on the heatsink but made all the difference as it does not overheat anymore. Something like this would be ideal in my opinion.
I’ll attach the STL’s. It was made for my own simplicity and I quickly modified it route the water cooling and wires through so it’s far from perfect. You will need to pause the print from the rear part at the correct layer height to put in 2 x stainless M6 half nuts (max 4mm high). The motor mounts with 4 x M4x70 cap head screws. The two parts bolt together with 2x M6x50 cap head screws. Your water pipe should have an OD as close as possible to 8mm.
Again everything could be designed slightly better to reduce weight of the hardware but it’s simple and has never failed me.
Rear mount for Axis 19mm
Front mount for Axis 19mm
I’m all ears if anyone has any suggestions. I’m happy to modify the mount and reshare!
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… and we’re not limited to 3 packs of four cells per row, could be 4 or 5 packs inserted in tubes with a round nose so long they are positioned on a balance point.
2 rockets below the baord!
Or cigar tubes with screw caps, streamline, easy to 3D print / waterproof / connect (Amphenol connectors) / replace on sliding guides: tool-less if inserted backwards (the pressure of the water pushing them to a stop)
Coffindrive 
It fits up to 10S4P (18650) or 10S3P (21700). The front will be cut blunt so that a light 3D printed/molded piece attaches to it. Base can be injection molded, 3D printed or pour molded with a 4mm aluminium cover which will also be the ESC heatsink.
With the 3D printed ends…
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I have an interesting problem on my efoil, with just a small touchdown i sometimes get the foil bucking like a horse to throw me off the board. I guess it’s turbulence that reaches the wing and disturbs the flow.
Aren’t all these below board solutions suffering from the same or even worse? I mean, it looks handy with a small box on the mast but actually, recessing a hole for a box in your board and sealing it is a 4 hour job.
Not so much turbulence as a weight distribution problem. You should be able to counteract it quite easily.
They do suffer from a breaking effect when they hit the water, but that’s why I prefer adding a little extra length to the mast.
Modifying all your boards reduces the resale value and also means I would need to mod multiple boards. I like this solution because I can both efoil and foil assist with it. I can also use it on boards from 24L up to my actual efoil volume boards.
thanks all. I’m not ready to move forward on the battery under the board yet. It’s going to take me too much time. I’m refocusing on my initial objective which is to cool the controller and have a very limited footprint under the board.
This will be cheap (30 euros) and I’ll add myself an 3mm aluminium plate with 3M 5200.
I’m going to use the USBOX rails to attach it.
BUT, this may create a challenge. Today I’m using a 16A (3x2.5mm2 copper wires inside) cable that goes to the motor… if I go this new route… the same cable… will NOW only use two of the three 2.5mm wires… to carry the negative and positive current of the battery pack to the ESC.
what ya think?
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I’m not sure sbout that, it truly is like a bucking horse, not just a shifting of weight (which is what i get at most touchdowns). Buut, i’m not in any way a skilled rider compared to anyone that surfs, i’m too slow in the reflexes. I think that won’t get much better before another 1000hrs on the board and only if i ride more waves 
Need increzased coolling, and maybe smaller prop depending on your kV and motor. Cut mine to 140mm Not crap but definitely not 100A phase unless ideal conditions.
I added thermal pad to box, increzased temperature de rating to 95°c max, start at 85°
It is inacceptable from maytech to sell a kit with this setup that will not work unless heavily modified/tuned.
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Awesome @okp !
Is this 12s2p?
Which Takoon Board and size is that? I am thinking about to get the Slate SW.
At the moment I have a 10 liter pump foil board. Hope 10s or 12s will be sufficient for that.
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it’s a takoon slate v1 4’6 - 35L. I can definitely lower the volume, likely 30L on 4’2 or 4’3 if I go Benett’s style on my next custom board.
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