When I’m cruising flatwater, I’m looking to pump around and catch boat wakes. It’s great for that. I use the sillyshort advanced fuse, and it’s very lively in the pitch direction. It is thin and slippery, takes a bit of finesse to pump compared to a thicker slower wing like the 1310, but goes much faster. It also works well for dock start, if you already have dock start skills. It doesn’t roll effortlessly, but it’s ok in roll, and not completely locked in like the 1310.
I only ride efoil, at least for now… do you think a wing like this would be good for efoiling?
I don’t think this wing is the best choice for an efoil. You don’t need his pumping ability or his glide. Due to the span, you will be limited in carving. I think the Art 999 or 899 wing line is more suitable.
It could work like this, if need be you could mount a small oil cooler too, but i think the first should be to evaluate how hot it actually gets.
My objection to the tubes on the outside and getting good seals against inlet/outlet tube etc is that it will add weight and most of all complexity - it will be hard to make something nice looking, you know…
Yup, after the initial excitement wore off I came to the same conclusion.
Too much weight, points of failure and complexity.
If I can get 10 amps/cell on my 5’2" 40 litre board, I should be good to go.
I have ordered some 3.5 mil ziplock bags that I’m gonna put the battery into. If my temps run too high I might try adding some frozen gel packs with a little fan blowing over to keep it cool in there. Hopefully the battery will be safe from any condensation the gel packs produce, but maybe the fan will prevent this anyway and battery should be water tight in the plastic bag.
On the brainstorming side of things, you might use a phase change material (water/ice functions as a pcm but batteries don’t like too cold temps)
Immersion cooling the batteries to soak up heat with a pcm that starts melting at 50deg C or so would be interesting to try. I know i checked this some years ago, found some materials with the right spec but never tried it.
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Good point on the direct contact.
I was actually considering using silicone non-conductive thermal cooling putty in between the battery and the gel packs.
If you don’t know what that is check this video at 00:45: https://youtu.be/1KXRtSAv37A?t=45
The new Flite cells use a phase change material apparently, never seen how they do it. The EGO lawn mowers use it as well each cell is wrapped with it, but makes the pack less energy dense.
For the frozen gel packs, do the maths - how long much energy does it take to get if from cool to 55°C to see if it make a meaningful difference. If you don’t like maths then put one in the microwave at ~300w and see how long it take warm up. My guess it that it is not worth it.
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Hadn’t heard of phase change materials until Lars mentioned them earlier. Definitely gonna look into that.
A 650 gram gel pack lasts 15 mins in the microwave set at 300watts with still a enough ice in the center to be effective. Not bad, 2 or 3 packs might get you 45. I know it’s not the most elegant solution.
Also unlikely to be burning the battery at the full 300 watts continuously.
Real world testing is needed though.
Hi Larsb,
okay so coming back to this idea, I have done a little looking into pcm’s now I am wondering why you think 50 °C instead of around 25 where the battery ideally should operate at?
I found a source that produces 1 gal bottles of pcm for a range of temps so if the I pull the trigger want to make sure I’m getting the right one. Thx
The reasoning behind it is that it is the phase change (melting) that takes energy, if it’s a warm day and the pcm has a melt point at 25 or 30deg C then all the benefit of the pcm will be gone (since it will be liquid already when you start riding)
If you have a pcm at 50degC then it will be a threshold where (in theory) the battery heats up to 50 gradually, then stays there until all the pcm is melted. It’s a balance of what kind of ambient temperatures you will have
The PCM will have a specific energy that you must check to see if it’s worth it with the volume of pcm you will use.
Let’s say the pcm takes 100kJ/litre to melt then for 15 mins of intense riding, 900s with 300w heat created in the pack gives 300w x 900s=270 kJ of energy and you’d need 2.7litre of pcm (these are only example figures.)
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Great, I understand all that but I think you are not considering I plan to cool the PCM first, so I will be starting with it solid. I found a PCM that has 200 J/g latent heat so for 30 mins of cooling = 1800 seconds.
Mass of PCM (in grams) = (300 watts * t seconds) / 200 J/g
= 300*1800/200 = 2.7 kg
Wouldnt this be better considering it should keep the battery at a more optimal temp? Only catch I can see is the hassle to cool it first but if I buy the gallon I could make 2 packs and keep one on the beach in a cooler of icewater while the other one is turning liquid.
Ideally you wouldn’t want to keep the ambient temperatures out (to keep pcm from melting), instead you want to be able to use the ambient temp for cooling. This would mean the pcm has to have a higher melting point than your max ambient temp.
I also think about the days when you do some riding, chill on the beach, then ride some more😎
It could also work with a dual pack and cooler but i think there are disdvantages: you will need to have to leave stuff on the beach and have more pcm if you want to handle most of the heat just with the pcm. It’s better to have it to shave off the peak temperatures, at least that’s what i assume.
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Okay you have convinced me now. Ill look for something above ambient then, you mentioned you had some PCMs in mind, care to share? I was thinking Lauric Acid, it has around 200 J/c and melts around 43C.
I might have messed up a bit choosing these batteries but this a fun experiment for sure.
It has to be isolating if you want to do immersion cooling and all acids will conduct.
It was maybe six years ago i checked it up so i don’t remember but i think it was parrafin-based, i found an online source for small quantites.
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No, I decided against immersion just gonna put packs on top.