I have one more question. I have built a 20s21P massive battery with used LG MJ,1s (10A) for my outboard that Im not happy with since it’s only 3kw.
Anyways, it’s a split battery of two 10S21p stacked on top of each other.
Let’s say I’m not particularly keen on buying new cells and I want to limit battery work… What do you think about this:
-splitting the battery in two
adding 2S, so each becomes 12S21P pack
limiting current draw at BMS and ESC to 170 peak for 10s and then max 150A (the cells in parallel new should handle 210A but this is used in decent condition but I still don’t want to push that high)
this would save me tons of time, work and money since I don’t have to buy more cells and build it from scratch
It’s gonna be on the heavy side, but I’m ok with sacrificing being nimble. I also remember reading somewhere that they recommend higher weight batteries for beginners. What are your thoughts?
Why, so if it hits you, it hurts more, and you stop efoiling? Whoever said that is a complete muppet! The lighter the setup the easier it is to learn and carry around…
At the learning stage you won’t have any reason for high current. It’s only once you really start carving and accelerating fast that you need the extra power. I’m 95KG and seldom use more than 80A unless I really accelerate fast.
There’s no reason you should run more than 14S14P battery on an efoil ever. It just becomes a heavy and dangerous burden otherwise. You said you like speed, so 14S14P should work well for you. Then configure the rest of the cells into a format where they can be attached to use on the outboard.
Big thanks and I appreciate you all take the time for a Newbie like me on this.
So… If you were me. I got a 10S21P pack with 10A cells (new but I don’t want to risk running it at 3C - preferably lower than 2.5C). Given your answer 80A it should be totally fine at the parallel lines already and I would love to minimize the battery pack work this time.
Should I just keep it as it is at 10S… Or make it a 14S21P or a 12S pack? I don’t REALLY care about the speed for the foil, but more about efficiency and getting it decent. 10S is pretty low and generates a lot of heat and to me and bottom voltage at empty is only 30v… Adding 40 cells more in series (12as) isn’t that much work since I have 80 cells in a box tested and ready too, so no cost and it’s easy to extend. Maybe 12S is kind of a nice balance since 14S would add 80 more cells making it damn heavy? I can’t really reduce the parallel rows because I don’t want to increase the risk of pushing the used (but tested) high capacity cells too hard.
8S and 10S are fine for a foil assist, but even at 10S I found myself pretty much at 100% throttle most of the time.
12S I find myself between 50% and 80% most of the time and then 100% when I want to be fast.
14S I find myself at around 40% - 60% most of the time and then higher up for speed. I seem to enjoy 14S the most because it just has better acceleration when I need it and a very fast top end if I decide I need it.
If you are seriously determined (which you seem to be) to leave the battery at 21P, then go 11S like the new foil drive voltage. That will give you a bit more than 10S to make it more exciting but not take it too much past. You have 35 extra cells weight over a 14S14P, but maybe thats the sweet spot for you.
Adding more cells in series reduces the risk of pushing the cells anyway if you cut down on the P side…
I went from 12S14P to 14S10P and the cells are perfectly happy.
Maybe you missed it but the current draw is nowhere near 150A on the battery side on an efoil (at least at higher than 20V battery voltage)
Calculate with your voltage and 3kW estimated power to get the current
I’ve run 10,12,14s and i’m a slow rider, these voltages don’t make a critical difference to me most of the time. Therefore I’d recommend to just start on 10s and get more riding time to figure out if/how you want to optimise further. You’ll be able to use the existing batteries and when you’ve got a board and time on it you’ll know what’s right for YOU.
Thanks. So then I’ll just stick with 10S. I never thought about the fact that battery and ESC side of things had different current levels for the same kW being pushed to the motor. Like you say, I could just 3D print a larger case + add more in series if it really doesn’t work out. What scared me was the rifle case thread where one guy was posting that he couldn’t get up on foil and I wanted to avoid getting stuck with a case that I could not get up on foil. The reason being that the rifle case has A LOT of resistance in the water given it’s sub optimal shape. So… Is 3kw enough for this project or is that advice for standard surf boards?
I have two ESCs;
the 100A 75100 model water cooled
350A 75300 water cooled
The motor is 85165 (max 19500w)
Am I wrong but at 10S the 75100 model ESC would get issues providing enough current? It would give max 42vx130A peak for a few seconds but it would quickly go down. I could stick the beefier ESC model on it but I was hoping to out that on my next electric outboard instead where I really want to to push the 85165 motor to the max.
Cheers and thanks so much for taking all this time to answer my questions! Highly appreciated
You’re still missing the basics of it. The 75100 will not be anywhere near enough to power that motor to the max. Look up the (battery) current capability of it and compare to the power rating of the motor.
Regarding the power needed for a rifle case efoil: frankly i think they are like surfing an ironing board
It seems so alluring to take an object not made to be a watercraft: not streamlined, harder to ride, easier to get hurt on and build something as commited as an efoil with it. It’s making things a lot harder than they need to be for a first build / first ride, the equivalent of renting a racing kayak for your first paddling trip ever
What i mean is: if you need a lot more than 3kW to lift then the way to fix it is not with more motor, esc and battery. Probably the wing is too small, your weight too high or the board(=case) choice poor. Build smartly😄
Ha ha. Yeah you are right. The RPMs for that isn’t right, prop would be too large, current too high etc. It would just be incorrect in most ways I realize including the use of these LG cells.
Well the original project ideas was correct, but that idea was my 84v 5.4kwh battery pack, the 19kw Flipsky motor with ECS to make yet another outboard. So for that original use case, the components are correct. Peak 19kw and continuous 8kw is like running a 10hp stinky gasoline outboard which is perfect.
Then I saw this efoil video and damn did I enjoy the idea of building that too. Maybe even combining them in one… And my brain went a bit on overload.
Ok, I’ll make my outboard conversion first as planned and when that is complete, then order the appropriate 65161 Flipsky motor and dual use the 350A ESC. I need that stronger 19kw outboard motor because the current outboard from my previous project is too weak for my quite large family sized dinghy.
I was more hoping that I could dual use the outboard build motor/ESC for my eFoil project, but it will just be a the wrong components for this eFoil use case I see now. Selecting the 6kw motor for the outboard motor would also be incorrect since it would be too weak.
Well well. I’ll post the Outboard pics when it’s done and continue with a better though out plan for the efoil… Probably some time after new year It’s time to start building the motor/mast mounts for the new outboard this weekend!
Hi. You are in somewhat similar problems as me regarding power (but I very drag-y object of 2m and 130kg). I’ve decided not to go with 85165 motor but with 65161 and 350A ESC from Flipsky. One day I’ll reuse that ESC and buy 85165 motor for my future rubber boat.
Have you considered going for 21700 cell size?
For now I am set to build with this high capacity high amp cells: Samsung 21700-50s 5000mAh, 35A. Battery config will be 14S10P (or 14S9P).
Yeah pretty similar No I’ll probably go down the path discussed in this thread, where I split the existing pack in two and then I will have two 10S21p packs as a starting point. I don’t enjoy the battery building too much so I’ll just use those. If they work, it’s great. If they won’t get me up on foil I’ll increase the voltage step by step.
I’ll use this foil in salty water and my life isn’t worth risking for a hobby. Preferably I’ll keep one 10S for the salt water and maybe I’ll extend the second to 12 or 14S for sweet water lake driving if that ever becomes a thing.
I have a pretty fun idea of using a strong wood core, 3D printed shape mast and then laminating it with carbon fiber for the outboard.
The 85165 has a continuous 8kw output, but below 50v and 150A that’s won’t be reached. Still, it’s gonna be much stronger and appropriate than my current 3kw outboard (4N torque) conversion I can’t get up on plane with.
battery building is not as half as bad as playing with resin. I’ve made solar electric catamaran (4.5m kayak + 4.5m fiberglass hull) 6 years ago and I’ve hated resin. The smell was unbearable. But it was a sweet ride - strongest 12V trolling motor(I think 65 lbs of thrust) and 120Ah solar deep cycle AGM battery. It could pull 53A continuous and it was a little too much for it… but better then with first 50Ah 12V AGM battery. Between was 245Wp rigid panel and some aluminium profiles for solar.
How will you charge battery. B
What about BMS?
I’ll probably just order an appropriate 1kw charger from Taobao in China.
Sadly I now have two 72v chargers and BMSs that I’ll have to sell. It was kind of neat to charge at 1.5 kw.
För BMS I now bought a 200A BMS with variable number of strings (7-16S). I hate that I used to buy the Daly ones that can only be used for specific S number. But I wonder if maybe it possible to use a Daly BMS with fewer of the strings connected. I just doubt that they actually are fixed. But who knows…
I was also considering to go without BMS and to buy balance charger instead but I am probably going to go with JBD BMS not to worry about everything when I borrow it to someone
Yeah I went with them too. Fuse + BMS for IF you fuck up. From what I’ve learnt people often think the BMS will cut if shorted, but they mostly don’t.
I just don’t get why we shouldn’t and all the professionals do add BMS and a fuse. There’s so much protection if you do add them for a reasonable price.
I put my efoil on hold to focus on the cad work for the outboard now. Moving on well there and I hope to have the first complete draft done this or next week. I am striving to have as much as possible 3D printed, but there are several components that require other materials to be able to hold the forces created by the 85165 motor. The tricket part until now is the motor mount that I want to be able to have variable pitch mostly 3D printed with nylon or ASA.
Waiting with anticipation for the new QIDi X Max 3 I ordered at black friday
Hmm… Seems easy enough if that really does it. Don’t have a 10A discharge … I have a 5A variable DC source but that ain’t enough. Guess I could just connect one of the 10S packs and then run a motor to 10A. Haven’t played with VESC yet - maybe there’s a way to tell the ESC to run at 10A?
Aha, the guide link was mostly to show that there seems to be a programming option, where you might be able to change number of cells. Calibration is nice and you could set current in vesc if you want something specific but it won’t need to be 10A, just enough to give some kind of accuracy in the calibration, be it 8,12 or 20A.
It’s time to start building the motor/mast mounts for the new outboard this weekend!