Pacificmeister Build Info and CAD Sources


I’m not sure I believe the specs, but here is a dirt cheap 120A DC solid state relay…


I used the same kill switch and also cheaper ones which can only make a short when unleashed. With both i sometimes had electrical feelings in fingertips when touching it, dependent on how wetted or immersed my body was. I talked to a boat equipper about it and was confirmed that all “normal” DMS could cause problems like this due to their cheap and non forgiving design. There are military style built, but not available for us. Sealing from outside does not help, i disassembled the DMS you are using and the sealing is made from a single large rubber membrane which transfers the forces for the plate which toggles between the contacts. So this membrane separates the contacts from the ambient. If it is not tight, the switch and its contacts get flooded with saltwater. Than there is a small red rubber cap on top, to protect the spring from contact with ambient. This part is useless, it cannot protect anything and generally fails in any test. Maybe it increases electrical resistance. See also Risk of electric shock

I feel we are using the wrong approach:
For cutting power when falling we need a “normal” path to switch motor power to 0 without damaging ESC or gearbox. This DMS could be integrated to the remote. The binding should not be lost.
For practical reasons we need a relais (or a switch) which cuts power from batteries, so they cannot discharge. This main switch could be realized by a reed contact in combination with relais or by other means. This cuts battery like a fuse. Binding will be lost. Its good if you can switch from outside with all boxes closed. You can toggle it also to force a new binding while on the water.


I am working ok a 3D printed relay that uses a solenoid to connect the batteries.


Thanks @PowerGlider for confirming that these kill switches are useless. I lost the red little cap immediately. Seems hall or reed switches are the way to go. I used a simple hall switch sensor before with success, receiver ground connected to signal pin which is pulled to ground with a magnet close by. Didn’t work anymore with the arduino remote experiments so I tried that stupid kill switch.


Hi @MaB, yes I had that strange on/off pulsing which think killed my Parker. It happens sporadically and I think is not related to the remote. Something the ESC decides to do, not sure why. When it happens then the only way to fix it is to open my battery box, unplug power, wait a few seconds and reconnect. That is not too much fun out in the ocean in the waves, got zapped a few times when touching my battery cables with wet hands. Better swim back.


That is cool, mechanical disconnects are nice because of the high achieveable isolation voltage. If you complete it, please share some details.

I‘m actually working on a circut board design for a mosfet protection switch, but it can only switch 100V. The nice thing about it is a crude adjustable overcurrent protection at currently 150A that should in theory switch off in about 25 microseconds. I have not yet tested it, but the components are about 25€. The output can be switched by a small low current reed switch through the watertight battery casing using a magnet. If anyone has some advice on PCB layout I will share the KiCAD files, otherwise I will first make my PCB and test the circut before posting it.


To avoid to have to open the battery compartment, I purchased a Vedder style antispark mosfet switch on esk8builders forum, 5 mosfet, 100amp. It work with a no-nc switch but it’s not that difficult to find an IP67 button. Though is not meant to cut power while under load (mostly the ESC won’t be happy!) but to reset the system like Pacificmeister did, I thought would be the thing!


Why would the ESC not be happy?


@MaB That‘s about what I‘m building, but I‘m adding the overcurrent protection. I think you are talking about these eskate antispark switches. Those are essentially Mosfet-Transistors with some resistors, capacitors and diodes to get a slow turn on time with limited current while the large capacitors on the ESC charge. Turning off is quick. You could add a reed switch to those. That would be a simple way to switch the battery on/off without opening the case. Edit: original github schematic for electronic antispark switch, we‘ve had some thoughts about battery switchin before in the thread Risk of electric shock
@MaxMaker I can imagine a few things why an ESC could die from cutting it‘s input power while running a motor, but I won‘t admit that I have made some of those mistakes already :sweat_smile: :
If you cut the power while the motor is still turning, the motor will generate current into the esc. Where the current will flow is uncertain, some mosfets may still be on when the microcontroller stops. In theroy a ESC could be immune to such an uncontrolled state, but some of mine have not been in every case. Esspecially my VESC did not like it on the teststand.


Ok, so the Arduino that runs the relay will first cut back the throttle and then disconnect the batteries.


It is two different things. With the fall detection you just reset the power to 0 or brake.
With the main switch you disconnect the battery from load.


Can you post picture or schématic and connexion to arduino to contrôl relay ?


Not yet. 1234567891011


I have drawn a quick schematic for @giloris and @MaxMaker, for switching a battery relay with an arduino. I assume you will use a similar relay to the one discussed in the topic “I think I found the right battery relays”. I’m only a mechanical engineer and have only simulated this schematic with generous assumptions. I did not build and test this as I currently don’t have such a relay. I assume it will work as I have left huge margins and the simulation went alright, but use it at your own risk. The components should be available from pretty much any electronics distributor, I searched to find the components in the schematic. I assume you will use a 5V Arduino. I have not checked if it will work with a lower voltage microcontroller. It could easily be adopted to be switched with a reed contact and a magnet.

How shall I power the safety cutoff relay?
How shall I power the safety cutoff relay?

@pacificmeister, can you tell use something about the current with your setup. which prop you’re using? how much is the max. amp (board on the water), avg. amp (during the ride). thanks a lot, beacause i’m still try to find some waterproof connector for the high current.


For the motor phases I tried many types of plugs and connectors and they all had issues. Either too bulky or they got hot and my solders came loose. I since bought a big crimper and don’t use plugs anymore, works reliable. On the battery side I use these ones, they also have anti spark integrated. I like them a lot: Amass AS150 Male and Female Anti Spark Connector Plug Set for Battery, ESC, and Charge Lead

Broken Lift Efoil
Troubleshooting burnt off Seaking ESC

pacificmeister, For the wires that connect to the motor are you using a dry crimp link instead of solder straight to the motor wires?


Hi pacificmeister
Do you mean , you dont use motor connector on sss 56104 (bullet connect ors) , you cut it ?


Cut only if you need/want to save space in the motor tube, see difficulties discussed above with removing the isolation from the copper wires. Easiest unsolder the motor connectors and crimp to wire.

Here my crimping machine, i love this device: IWISS Wire Terminal Crimping Tool 6-50mm² Cable Lug Crimper Cu/Al Terminal Ratchet Electrician Plier (AWG10-1/10)

Here the copper crimp tubes: 8 GA AWG Copper Crimp Butt Connectors Battery Wire Cable Install Bay 25 Pieces

To save space in the motor pod I cut these copper tubes in half. Still plenty of length and strength.

I use the same crimps to connect to esc. Solid.

Troubleshooting burnt off Seaking ESC

Hi pacificmeister
Thanks for these details .
I have a question to fix tube on fuse foil .
If I fix tube only on the mast the
Weight is too important and piece is Broken
Havé you this’problem ?
How do you fix rear tube to the foil fuse ?