OKP's build - Another eFoil in France!

okp · November 6, 2021, 5:54pm

this will do the job ! two more and I start to weld!

I’ll use 0.20mm nickel and thicken it with desoldering braid, everywhere.

okp · November 7, 2021, 10:38am

Starting with parallel junctions. 0.20mm / Weld Pulse Duration 0.24mms on my Maletrics Spot Welder. Welds are strong. I forgot how time consuming it was to make batteries.

I also took the opportunity to replace my 0.4mm nozzle and replace my old tube with Capricorn one.

okp · November 11, 2021, 8:25am

hey, slow move is better than no move!

I’m having some challenges with my 3D printer and the PETG filament. Maybe he’s a bit too old but I’ve ordered a new PETG filament and see how it goes. It just delays a little bit my battery building but time is on my side.

In the meanwhile, I’ve received some parts.

200A Fuse & Fuse holder
Desoldering braid (to reinforce my batterie series connection)
Amphenol connectors

okp · November 12, 2021, 11:13am

I managed to print the bottom layer and get the PETG prints working again and I’ve also received some cables (not the AWG8 yet) and the 14S BMS

the top cell holder is being printed and once done, I’ll move to the overall battery enclosure box design.

pablo_foil · November 12, 2021, 11:53am

I’m following a similar approach regarding the esc, but instead of leaving it outside, I will leave it inside (see attached pic).
I want to do this since this way I still get the single-cell low voltage cutoff.
I connect the output of the bms to the receiver, in series with a reed switch , attached to a leash+magnet, so that if either a single cell falls below the min voltage or the leash is disconnected, the rx loses power and the motor is turned off after 1 sec. In the future I might replace this with an arduino so that there’s not a 1sec latency between signal loss and motor cut off…

okp · November 12, 2021, 3:39pm

“regarding the ESC”, you mean the “BMS” ?

Got the RS232 connection for the balance cables that I will put on the battery side.

pablo_foil · November 12, 2021, 4:47pm

“regarding the ESC”, you mean the “BMS” ?

Yes, sorry.

Yep, I understood the idea, but I decided to keep the BMS to turn off the rx if one cells falls below the min voltage. The ESC will only stop the motor if the total voltage falls below a threshold. I don’t know how likely it is for a cell to discharge faster than the others, but better safe than sorry i guess…

okp · November 12, 2021, 6:47pm

that’s a good idea.

Print is done ! tomorrow I start the battery enclosure!

okp · November 13, 2021, 8:35am

I launched the print. I will need 4 prints to make the box. I decided to have a 3mm bottom printed and I will cover it with epoxy/carbon. It’s not PLA but PETG.

okp · November 13, 2021, 10:49am

update of the day/morning.

The print is still on going. I went a bit too conservative on the print settings with Cura. I found a way to optimize them and reduce the print time to 12 hours. Let’s see on the next print.

I continued to weld the parallel nickel bands on the battery. It’s all done. Next phase is series.

I’ve also received the water-cooling system and thermal pad that I will use to cool my ESC.

last but not least, the shrink tube.

I also installed this on my 3D Printer enclosure, so it automatically launch the ventilation to cool the enclosure when needed.

Sliman_O · November 13, 2021, 11:15am

I would recommend not to print the battery spacers in PLA. Same for anything that will heat (even 50°C).

okp · November 13, 2021, 11:17am

yes, it’s PETG. This should be fine Temperature resistance is 85ºC. PLA filament is 50°C/60°C max.

Even if that melts using PLA, the pack will be ultra rigid and solid (wiring braid helps a lot). So all in all, let’s say that cells holders are more used here to make a fancy pack and easy assembly.

I’m looking for a 9mm tube that I will use on my water-cooling system. Would you recommend me anything? Thanks!

okp · November 13, 2021, 1:53pm

back to the battery pack. I was hesitation to use 10mm strip 0.20mm reinforced with desoldering braid to make the series links.

I’m opting for another solution that I will weld on top of my Ps. 0.20mm.

https://fr.aliexpress.com/item/4000242593023.html

I will get much more contact surface, especially with my existing parallel setup.

I’ve ordered 30mm x 0.20mm thickness

Sliman_O · November 13, 2021, 2:45pm

Not entirely sure about this. Ask @Alexandre about his issues with his pack. Nickel strips might fail under repetitive vibrations, especially when you start learning and fall quite often.

okp · November 13, 2021, 3:14pm

no worries, I ride and build electric skateboards for quite a while now and I can tell you that the vibrations are very different. Issues often come from poor welding (or inappropriate pulse).

Alexandre · November 13, 2021, 4:58pm

Here a pic of the pack , 8P of 30q , overheating under continuous load, printed cases and even shrinking tube on balance wires melted …
Vibrations in one things , in my case it was plenty of crash over 30km/h with a hot battery in front of my board

For sure I will not count on printed cell holder again for Efoil application , eSkate cannot be really compared I think because it is harder to run full load for several minute and I guess you will crash only one time

okp · November 13, 2021, 5:13pm

got few questions for you:

what is your experience on ESK8 builds ?
what are your pack specs? what does your amps draw looks like?
you mention overheating, what temperature did you measure?
what material did you use on your cell holder and printed case?

What you are showing could be the results of many things, variables which are not really directly linked to the use of PETG. That’s what I’m trying to clarify. If you have your balance shrinking tubes that melt… I believe you may have other problems to solve than PETG, but I may be wrong.

Worst case, I will sink silicone into the battery and call it a day !

Alexandre · November 13, 2021, 7:05pm

I built my eSkate with a 6374 and a pack off lipo 2x4s 5,3A
For this battery it was a 12s8p of 30q running 90A (vesc max setting) constant discharge
Could record pack temp during load , but after back to shore it was hot to hold and switch the packs
Module are professionally made in Petg and fully tested under high load and vibration but NOT mid load and hard crashs, i believed that was the problem, heat building up over 10-15min

Clearly overheated and melted , always better than my lipo taking fire and pushing the top of my case …

okp · November 13, 2021, 7:53pm

Thanks! based on your feedback, I think I will be fine.

Wingaddict · November 13, 2021, 9:50pm

Hi OKP, I am struggling with my 75200. Everything fine in air with no load 16000 ERPM but Impossible to get more than 50 Amp in water ( Flipsky prop) and 5000 ERPM only. As it is the potted version I can’t see whether I have one of the bad resistors serie ( purchased on BG). I should have bought a non potted version to have acces to the resistors and immerse it in Corrosion-X as recommended by @Flightjunkie ( potion magique ) Some succeed with this ESC but I am near to give up and move to another ESC…