Safety with eFoils

I have the same Flier 400A esc. I used to have a lanyard coupled to the reciever signal to esc image but because this device started to leak it did not stop the motor as supposed. It is also sticking out of the board and could potentially hurt so I removed it. Now I rely on that the motor stops when I release the trigger or that the reciever loose contact with the tx because I hold it under water. It seems to work fine and it is nice not to have the rope around the foot. Does anybody think this is unsafe or have the experience that the esc do not stop when it loose contact with tx so that the board could go away and hit possibly somebody?.

It depends on the inplementation on the reciver side, but it should work. In my lab setup I added an additional hall sensor to the receiver side. Magnet in front of hall sensor=OK. If the magnet is removed, the thortle slows down to 0. With a strong magnet it should work through the lid of the electronic campartment. Even if you pull the trigger, it stops the foil from running away as soon as you fall off and remove the magnet. Haven‘t tested in practice though.

What about this thing? It has a rating of 100A with 500A peak for 5 seconds and voltage range from 12V to 48V. Don’t know how accurate this is though.

What do you mean by ‘automatic 100’?

You would need to waterproof the button, as it is only IP65. Also you can’t cut the battery power with this (I think this might kill the ESC anyway if you’re unlucky), only receiver power - which you need to check if it’s safe to do.

Apart from that I can’t really imagine this being practical, you need to stand always exactly on the same point. And normally you do balancing steps around the center position of your feet during the ride.

Has anyone thought or heard of the “durajet”


Maybe little old school thinking but would feel uncomfortable having to relay only on the ESC to stop power supply to the motor in case of loosing control / falling of the board. Not only about safety for the driver but also third party, if the board continues proceeding, can crash into swimming kid as an example.

A high current relay type solution in combination with a kill chord would feel safer. Still having the ESC of course as back up. Is it so that cutting the power before ESC is better than between ESC and motor(if considering potential damages to ESC do to this prompt power cut)?

This will 100% blow the ESC if done during load.

This might blow the ESC and every electronic component connected to it, if you are doing this in breaking phase.

Problem is, ESC will work like a regenerative break while slowing down. This produces electrical energy. If you disconnect the battery, this energy cant be stored and will result in a rising voltage at the ESC. Then your weakest component will blow. Either the 60V rated FETs, or the 63V rated caps or the 60V gate drivers.
However, disconnecting the battery might work a few times if you are lucky, but is definitely no permanent option (except for a emergency button in case of fire or something).
Other thing is, that all mosfet based switches will blow/stuck open by disconnecting under load, so only SSR or mechanical relays are an option.

Long story short, program a nice fail safe onto ESC, test that this works instantly when receiver signal is lost and use a leash connected to receiver signal.
By that you don’t have “single point of failure”:

  • Motor goes mad => no run away, no fire, ESC cuts back since lack of BEMF
  • ESC goes mad => no runway since motor needs timed commutation for it to work. Still fire is possible if FETs stuck open => mechanical kill switch for emergency. But ESC will only go mad if something is shorted…like water ingress in electronics or temperature as high that things desolder.
  • Receiver goes mad => leash will fix it
  • Remote goes mad => leash will fix it
  • leash (sensor) mad => still receiver and ESC works separately, if stuck open ESC will failsafe, if stuck closed receiver will work regularly.

So only way to fuck this system up is to kill at least 2 components at once.
For me way safer than having a kill switch with either works and kills your ESC and electronic or doesn’t work and doesn’t help anything.

OK, thanks. Sounds like old school is not that good after all:) Yes was thinking about a mechanical relay. Better then to control this with the ESC. For fire and such emergency, would use a mechanical switch, BlueSea systems have such that can handle high amp.

Believe above also means than one can not “protect” the motor for high amps by having a fuse between esc and motor, if fuse goes big risk for blowing all electronics. So main fuse if any should be between battery and esc?

If you are talking about a mechanical fuse, then no you should not do that.
But all “smart” ESCs (basically all ESCs outside the hobby segment and even some inside) have current control feature, so you can active limit and supervise the current from battery and inside the motor. This is basically all you need (for motor protection), maybe some temperature sensor additionally.

Yes, in my opinion the only place where you can have some emergency cut off.

Thank you for that explanation. I have a swordfish 300 pro plus and the latter is equipped with a Switch, after asking the question if a full cut (Kill Switch) charge was feasible or harmful here is Carrie’s answer from Hifei telling me that it is not a problem…what do you think?

Hey guys I’m working on a boardcomputer with GPS and many other different features like cell voltage detection to make my board as safe as possible! I’ll share my project as soon as it is finished!


@pacificmeister that happend to me. I was riding the lift efoil and i knew i couldnt handle it anymore and i kickt the board away and i flew right onto the foil. That hurt, but i am glad that lift foil has a prop duct. Thats the reason i need to make a prop duct for 80100 motor. Look at my topic:

Thanks to all people i love the forum here:smiley:

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