First build from Haarlem

Hey guys,

Around a few months ago i came across efoiling and was absolutely stunned. So all i have been doing this past weeks is reading this forum and planning my own build. I still don’t know much so please riducule me when i make an obvious mistake. Any feedback is appreciated!

I plan on using the flipsky 65161 120KV, the flipsky 200A 60V esc, the erayfoil A1 remote, a 12s14p battery and the Gong allvator curve L. I’m planning on cooling the ESC with water inserted from the front of the motor clamp and pushing it up with the presure. If that doesn’t work i will have to use a pump. The ESC will also be put in a aluminium box.

I would love to use recycled cells for my battery as that would cut cost massively but i also don’t want to burn my house down. I found this site where you can get around 250 used 18650 cells for only 80 euro! Lot of Commercially used in Laptop Battery packs for Cell Recovery – Battery Clearing House

I would rather buy from a local online second hand shop because there you do get one type of cell instead of a bunch of different ones.

I like to know if anyone has experience with used cells and if it’s worth the hassle. What are the things to look out for? If i buy used cells i want to make induvidual fuse wires like @Flightjunkie and others did in this post. Building an 18650 battery with individual cell fuse wires

Flightjunkie uses fuses on both sides of the battery but would only one side not be enough?

This is a pretty basic build but i do plan to improve on safety. I want to mount a cord on the front of the board. If the cord looses tention the motor will stop. One of my ideas was to have an elastic cord mounted on the board on which you attach de cord what will be held in your hand. In the board and in de middle of the elastic cord you will have a magnet that will be attached to a wire. When the rope looses tention the magnets snap together and close the circuit triggering a relais cutting the power of the system. A quick drawing of the possible system:

Is it possible to do this without the relais and use the ESC to cut of the power? I came up with this because i couldn’t find a simple tention switch. Does anyone know if they exist?

I know that these are a lot of questions but any help is welcome!

1 Like

The circle of efoil builders is closing in! I’m from Zandvoort and I’m at 80% progress of building the PM V1. I know: old fashioned but it was the best available option at that time. Second built will be like your setup.

I don’t know much about electronics but it seems to me that your idea about the kill switch is a bit complicated. It will be hard having tension on the cord all the time, cause your feet/ hands will most likely not be in the exact same position all the time. It needs to be very strong as well in case you fall off.

Why not use a standard kill switch like for boats (dodemansknop)? I’m planning to use it as you proposed to shut the power to my esc.

(Good luck with your built!)

I already saw someone efoil a while back in Haarlem on the mooie nel, so I’m not the only one in Haarlem!

You are right about the difficulty of keeping tention on the cord. Maybe if the cord is elastic I would have more wiggle room.

I didn’t want to use a dead man’s switch because I think it triggers to late. If you fall you could still reach the motor before the switch triggers. I could be wrong here as i haven’t used a dead man’s switch before.

I’ve had a wing foiling lesson some weeks ago on the Mooie Nel. Love that place.
Also. If you are interested, contact @Kwinty He’s got EV battery’s, and this will be lots cheaper than building your own.

@Kian thanks.

Having an open contact on the outside in the water isn’t ideal, think about all the corrosion, rust, water, and things it has to withstand. Not even considering the shocking hazard…

Killing the VESC this abruptly is something the VESC won’t like. For example, you fall off when you are throttling down, the VESC can regenerate ever so slightly, and now with no connection to the battery this energy can’t go anywhere but the capacitors. Since these are very small the voltage will rise and go over its limit and possibly blow up the VESC (ask some esk8 guys :slight_smile: ).

Playing with the PWM signal with an Arduino and a hall sensor with a magnet as a deadman switch can get very good results and don’t need to be on the high power side so much easier. If you set the VESC to brake when you let go of the throttle it will stop the prop immediately since there is no mass in there.

1 Like

If you build your own remote it is easy to set the PWM signal to 0 with a magnet switch with HAL sensor. You could also put an atduino in between the receiver and the VESC and add a HAL based kill switch to this arduino.

The top part is mounted on the board and has a HAL sensor under the half sphere. The top part has a neodym magnet inside the spheric plug. The small magnets around keep it in place. The plug is fixed to the leg with a short leash. PWM is set to 0 if the plug is removed with a delay of 50ms to prevent glitches. Works really well.
The speric shape is an improvement over a cylindric shape and allows to pull the plug from a flat angle.

This is exactly what i was looking for! thanks!

Is it possible to connect this idirectly to the ESC? Or do i need to add an arduino in between?

It depends, there is more than one way. Easiest way is to use a NO read contact under the magnet and put it between the receiver and esc pwm wire. Most escs stop if they loose the pwm signal, sometimes, a delay is configurable. Although this works, reed contacts are not very reliable and get stuck sometimes.
If you want to use a HAL sensor as I did, you could use an arduino with servo library, read the the pwm signal from the reseiver, check the Dead Man state of the HAL sensor and conditionally put the signal you read from the reviver to an output connected to the ESC.
You just copy the pwm signal from the input to the output as long as the DM state is OK. If the magnet is out, you set it to 0. Arduino servo library handles the pwm signal. You might need a filter for the HAL sensor, simplekalman filter works well for me.

A friend of mine pointed out an oversight. If i’m gonna cool the ESC with water comming in from the mast clamp, how am i gonna keep out al the gunk form the river/lake? The water isn’t that clean in Haarlem. Is this gonna be a problem? Or is cleaning it ones a month enough.

Hi guys

I kinda want to use the same board for my efoil as a want to use for windsurfing. What are the consequences for efoiling if I make a board that’s 2.4 meter long?

check my built “slow built from france”

i used a 2.4m sup board with the battery in front, for my first built, worked great, but it doesn’t help at all for shape turn and the front keeps to went to got down when curving, the battery up front did not help this also

a pain to carry but other than that for a fast made first board, worked great

1 Like

I have a 12s battery with LG MJ1 cells so max voltage would be 50,4V. I want a circuit breaker in my system but can’t find any cheap ones. Would this 48V circuit breaker do?

Yes those work, but it depends on quality , looks the same but they are not , good one ( tawain … ), cheaper made of plastic ( China …)

Hard to tell for a pics , I bought a branded one for a boat shop

Hey guys

I was stupid enough to keep my bms connected while i was soldering the balancing wires to the battery. I saw a little spark and it seems like one connector has shorted.

Now i got a weird reading in the ant bms app. For some reason cell 14 reads 0.9 V while it’s not connected. It is a 12 series battery and the other readings are correct.

Would this be a problem with charging? As a bms only decreases the charge of fully charged cells. Is it safe to charge under supervision or do i need to order a new bms? I know most of you guys are anti bms but i would love some advise :grinning:

We don’t like bms because we don’t trust them, especially after a spark and an incorrect reading , and since you asked, you probably already know what to do :wink:, so yes you should get another bms