Strassa's E-Foil from Austria

[strassa]

Hey @all ,

I built my first esk8, 3 years ago and found this forum on my search. Since then I basically read the whole forum and now made an Account to share my build in progress.

I studied electrical engineering in Vienna and started working August/2019 at an automation company where I am implementing VFCs.

So since I just started earning my own money, I want to do a mixture of full DIY/low Budget build (and focus on safety and relieability). So this is how my build looks like (work in progress):

• 80100 Motor Direct in water (only lakes around)
• FSESC 200A
• DIY 18650 Battery
• Old Windsurfer as board
• 3D Printed Foil

During Easter I started with my battery:

Overview:

• 12S9P - 18650

• Two different cells: 72 x 25R Samsung (from Nkon) 2500mAh 25A /very good P/V
  36 x K-Tech 18650P 2500mAh 12,5A /unbelievable Price/Value
  (long story)

• Single cell fused (tesla style) with ~15A fuse wire
  A battery main fuse 125A (selectivity)

-> that gives 50,4V 22,5Ah and about 1kWh

Battery progress:

3D-Printed “BusBars” 2,5mm² copper wire

Casing (300x230x86) with 3D-Printed spacers

Soldering… a lot, got a high power Soldering Station and only very short contact with the cells.

Charging batteries i missed charging:

Main poles:

Two XT90 (one XT90S) Terminals, one for Power and one for Anti-Spark key (also main fuse)

Current state:

Edit:
To DO - Battery:
Seal the Outputs:
Charging Port,
Voltage/Amperemeter (this is what the switch is for)
Charging BMS

I have 3d Printed a lot already (foil and mast), will show this soon…

[philippe]

Hello
you put a BMS?

[strassa]

Yes I use a cheap 12S bms from china (not yet built in) just for charging. The following scenarios can happen:

Overcurrent:
Current is limited by ESC to 100A battery current, if that fails there is the 125A fuse in the battery and if one cell shorts out I have the individual cell fuses.

Undervoltage: Will try to get the battery voltage on my remote + undervoltage prevention from ESC

[Tigeriki]

Great, i am curious about your 3d printed foil…

[Toto44]

you use 2 different cells in your pack?

[strassa]

yes, first i bought the Samsung 25R then a few weeks later I saw those K-Tech cells and had to buy those for 1,7€ per cell and 2500mAh. I did lots of thinking afterwords:

i run per 1s: 6x Samsung 25R and 3x K-Tech as you can see

both cells have 2500mAh, but that doesn’t matter since they are parallel

on my fuse limit every cell runs at ~13A everything above will trip the fuse

in reality: ~90A , I am below both rated currents (12,5A for K-Tech and 25A for Samsung) so its fine.

So all in all I should be fine

[strassa]

here is a sneak peak :

[Tigeriki]

I had this ideea too, as i have some inox tubes available. I stuck in the design. (And also eppg project) I have your motor too, are you planning to epoxy it ?

[strassa]

do you mean to epoxy the motor or the foil?

[Tigeriki]

The motor i meant. The foil i think is not necessary…

[nice2cu]

First HELLO and welcome from Salzburg!

I also reading month and month a lot and start with work in September last year.
So, i hope i can ride in Mai.

I think it is not intelligent to mix two different Batterymanufacturers!

[strassa]

yeah I know its not ideal, but with my limitations it should be fine, or what do you think happens?
I am from Salzburg aswell (Seekirchen to be exact)

[Tigeriki]

Did you design it ? I can work in Rhino and there is a lockdown for one more month… I think i will start working as a print takes long…

[nice2cu]

Crazzzzzy, i am from Eugendorf.
We often are for swimming on the Seekirchen Strandbad.
We are some peoples next to us and we meet us sometimes for riding
When Corona and we are finished, you go with us

[Toto44]

I hope your K tech cells will survive. For sure they have totally different internal resistance. The will get older much faster than the Samsung

[strassa]

yeah they are under more load (percentage wise) then the samsung cells, a few 100 cycles should be no problem though

[strassa]

I first wanted to coat the motor in epoxy, but since the air gap between rotor and stator is so small, I changed my mind and I will fill the stator magnets with 3d prints (here I will use some epoxy to glue them in place) and clear coat both stator and rotor with 2k clear coat, 2 layers I think.

[strassa]

Progress on the Low Budget 3D print Foil:

Found this Aluminium Extrusion:

Designed Inserts that go with the extrusion:

this is the extrusion with all inserts (and the motor mount):

A friend welded it to a base plate:

the result:

This is the cut windsurfboard with the wooden counterplate of the mast,
i will fibreglass the wooden plate and glue some threaded rods to mount the mast.

[nice2cu]

Did you plan to laminate the Mast with CFK?
I am not sure if that will broken…

[strassa]

it’s super strong, 8mm Aluminium plate, and we tested the welding with 150kg in all directions and no forming or what so ever