I was down in North Carolina for Xmas. Nice to hear some one else here in the eastern US is a builder. Its warmer there than New York.
Your build looks great!
I thought I saw that you already shared the prop faring (motor to prop hub adapter), but I can’t find it.
Do you mind posting the STL? My Chinese prop will be arriving soon.
Do you have any cutoff switch ?
no way man! Im from wilmington too! I guess you beat me to being the first kook on an efoil in wb. lol
Crazy man! Is your build up and running? We should look together sometime.
No net yet, I just started! ive been at school in charlotte. I just finished a custom cnc machine so im gonna work on building a good hydrofoil first, while I save up some money and wait for peters motor. I have an old janky wooden kite foil I made a few years ago but hopefully with the aid of CAD and some precision I can make a better one. If I come up with a good design I could make one for you too.
Cool man. I studied mechanical engineering at Uncc. Cnc sounds awesome.
That’s crazy me too! It would be unreal to see that foil in action
Let’s take it for a spin. I’ll dm you my number
So ive been having a ton of fun with my foil project for the last couple months. I havent been able to ride it as much as I thought I would but probably have 10-15 sessions on it. Battery run time is 30-35 minutes with 2x turnigy 20000mah 6s batteries in series. I havent had any issues with the motor or speed controller yet. I have had problems with the maytech remote. I think its pretty well know on here by now that the waterproofing is prone to fail. At one point my remote was not working even after a month of drying it out indoors. I was able to save it by putting it in the fridge for a few days. I got it wet a second time and yet again, a night in the fridge saved the day! I now ride with the remote in a ziplock bag.
Unfortunately, on my last ride my batteries bit the dust. It was pretty normal for these things to get really hot (about 130F) by the end of a ride and the batteries would even get a little puffy. The puffyness was usually temporary. These batteries have a 10C rating but in reality I dont think they are anywhere even close to that. Im pulling like 50-60A average with max of like 120A from my flipsky VESC 200.
I guess its time to take a stab at building my own 18650 pack like @Flightjunkie. Because I use these batteries for my ebike, I would like to keep the same form factor as the turnigy batteries. This would also allow me to use the same electronics enclosure im currently using on my board. I think i can build 2x 6S8P packs and keep each within the same dimensions as my spent turnigy packs. To do this though I have to get a little funky with the cell layout. The picture below shows what im thinking. The 6 cells of the same color would be in series and make up each of the 8 parallel cell groups. If I stagger them as shown in the model instead of putting them in straight lines, I can fit all of these cells inside of a box that would be the same size as my turnigy batteries.
If i use samsung 30Q cells (15A, 3000mah), i could get 24000mah per pack at a rating on 120A. I would be running these two packs in series so total would be 12S, 24AH, 120A rating. That would give me 20% more battery capacity compared to my 20AH Turnigy batteries. I have a couple questions fro the battery experts though.
- Would I be pushing the 120A rating of these batteries with my flipsky 65150 setup? Is this a continuous rating or peak? Is this rating accurate or way exaggerated like the Turnigy batteries?
- Do you think I would have issues with heat using this battery configuration? They are probably a little closer together in this config that is they were straight side by side. I guess this is a function of battery spacing for heat dissipation, current draw, and the number of cells i have in parallel.
- Can you guys recommend any good BMS systems? 6s 120A minimum.
- Recommendations for best places to buy these cells?
Any red flags with this? This would be my first battery build so im a total noob and would love some input from the pros! Thanks!
Sounds like I am might want to skip the BMS. Just read a post about someones van catching on fire! I guess as long as you have a decent balance charger, than maybe relying on a BMS might be riskier than just being responsible during charging and not letting voltages drop too low.
After reading more, sounds like the samsung 30Q is the cell of choice. Anyone know if i will have any heat issues with these cells in 8P and close packed diagonally? My max battery current is set to 100A on my VESC.
I ran 2 6s12p 30Q packs (35AH) and they are get fairly warm. Yesterday I got 35 min or so with that pack while mostly up and foiling… although I have a smaller foil. Looking at my data, I was around 50ish amps going about 16-17mph on foil.
I 3d printed a spacer to keep the cells a little apart. You don’t want the insulation rubbing through and shorting two series rows together since the can on the 18650 is negative. Read up on some battery building. Knowing what I know now after more reading, I would have laid out my packs a little differently, rounded all the corners on the nickle, etc…
Thanks for the input! When you say they got a little warm like literally just a little warm or almost uncomfortable to touch? My turnigy packs that just bit the dust hit like 140F on the outside of the pack. Who knows how hot it was getting between cells! I wonder if an 8P pack might get too hot?
Heres a video from the last ride I had before my pack blew:
Nice video. What wing are you using?
Check out the top of this post for specs and pictures. Its some cheap flat garoite foil/ aluminum mast fuselage setup i found on ebay a couple years ago. Cant remember the brand. way better ones available in the same price range these days.
So you’ll be running your pack warm (80°C) :
I’ am no battery expert but looked for the same answers for my pack.
120A (peak) means you’re pushing 6kw in your motor which if memory serves is the motor max power. Look here, metrApp from Ackermann using same motor :
I don’t think you’ll be pushing more than 100A peak battery current with this setup, so 2x 6S8P should be suitable for your needs. If you ever need to use more than 100A peak (peak means not continuous), then you’ll probably have to redo your calculations to draw around 10A per cell and stay under 60°C.
You might want to order from Nkon or Fogstar. Fogstar cells are shipped from UK and available with a discounted price for efoil.builders members :
Yeah, I think it’s a bit tricky to find a suitable BMS for our needs. I’ll be interested to know what Lift or Flite are using ? Anyone knows ?
30Q cells are the one used by Lift and by lots of dyer, not only in efoil. They are proven to be good quality cells.
Heat dissipation depends on your amp consumption. 100A continuous means you’ll be running your pack at around 70°C I guess, see curves I posted earlier. Thomas from @funboards.at is building kind of same packs for his electric paramotors, so no problem with this configuration I guess.
This is AWESOME info @Sliman_O! Thanks for the help!
You are right. I wont be hitting 120A. In fact, i revisited my VESC settings and my max battery current is 100A. I am running current control from my remote and RARELY if ever use full throttle. Probably 80% if im trying to get up and going fast and then back off to maybe 50 or 60% throttle while on the foil.
Thanks again. Love the plot and will def check out the vendors you mentioned.
I cant find 30Q cells in stock anywhere online in the US. Looks like most places wont have then back in stock for 2-3 weeks. Anyone know a place to get 96 of these things sooner?
Back in oct for 170 included shipping it was $514 (about $3 a cell)