ichiban said:
Not long after printing this cell holders & some other parts, I sent my Voron2.4 (3D printer) to a friend to upgrade/mod and do not expect it to be back in about a month. It will be a Rev2, reliable and fast. I really enjoy using it.
I can help you with the CAD design during my free time, and if your cell holders are not very fancy. After you receive the file, you can have it printed at any 3D printing service to you like. Printing charges should be fairly cheap. So you can save some shipping cost & time compare to shipping the 3D parts from Bangkok to you. Havn't asked yet, where do you live ?
I will post the CAD file here in case other members can be benefit from. At least, this is a way of payback from what I learned a ton here within this ES forum. After you use this cell holders for your pack, do pay it forward to others as well. We need it badly in this situation.
Hope you are OK with that ?
If so, just post detail of your cell holder layout here. I'll look into it.
....
I am in the USA, so, yeah, getting it printed here makes a lot more sense. I have a few friends at work (all Mechanical Engineers) who do 3D cad work, some also for fun outside work, and at least one that has a 3D printer at home. So, I might be able to get one of them to do the cad work, and also the printing. I will certainly share the models/drawings and any knowledge/lessons learned from this build with this forum.
Yes, that's what friends are for.
What diameter did you use for the cell holes? I'd assume that I want a little clearance for thermal expansion?
ID ∅21.28mm is what I found tight and manageable to put the cells in. The first cells holder is OK, but the 2nd side I had to use my body weight to force 30 cells in altogether. That did not hurt the cells skin unless you re-insert the cells in/out many times. You would want it to be tight fit rather than just-slide-in since plastic always yield a little especially for PA-CF in my case. It is tough & a little flex, weather proof - one of the strong 3D print filament fit for functional parts. But not all 3D printers can print PA-CF. FDM 3D printer is not like paper printer that you just hit enter and your work will come out beautifully. It still in the stage of early film-camera that you will have to manually adjust everything yourself, so the user need some skills to get a good print out of it. Years from now, we will get a point&shoot conveniences like mobile phone camera now.
After I put everything together, the pack is quite solid given that I made it thin-wall and compact - similar to your honeycomb. Still some space left that you can put temp probe among the cylindrical cells. In case you pick some other filament, dimension might need to be altered a bit, by the last decimal digit. Make sure you pick the right plastic. High temp to start with, durability closely follows. Layer adhesion must be very very good, you don't want it to shake loose during riding. I expect mine to last as long as the battery itself.
Some advise, should you decide to 3D print your honeycomb, it will be better to have a 1-mm tall walls to physically separate the Cu/Nickel pads from each other. So when put your Cu/Ni pads into place, they will sink/secure into places without touching each other - when assembling or riding no difference. Touching of pads means very high current from cells shorting - possibly be medium xxx amps in your 8P scenario. That walls will complicate your 3D print a bit, you will need supports when printing. But it is well worth it. :thumb: :thumb:
Just some info for you and the others who might be watching this, don't expect fast progress. I have VERY little free time in the best of times, but, right now is even worse, as where I work, my dept. manager left, his replacement hasn't been onboarded yet, so, I'm doing his job as well as my own.
We all are busy nowadays. That's better than jobless ! :wink:
FWWI, I'm an electrical & software engineer (EE degree, my job is mostly software, but, I do get to dabble in hardware from time to time, and certainly have good EE knowledge, LOL).
Same here. But software is not my specialties. More fun building/designing things. Give the headache to others.
For the curious, the specs of the build are:
160 Samsung 40T 21700 Cells, 20s8p
Daly BMS 20S 150A
Mine is the same SS 21700-40T / but only 20S3P spiltted in halves >> just wanna make it compact on my bike. My regular riding is <50km 95% of the time. Aesthetics is also one thing I don't wanna skip. I can add a 2nd pack for long trip. My BMS is Jikong Active Balance BMS from IC GoGo : https://www.aliexpress.com/item/4001192978656.html?spm=a2g0o.order_list.0.0.1f131802NFptub. A member (Dui, Ni shou de Dui) on this forum recommended it. This store is one of the best selling store in this category. Bought from them several times. Should be OK. My first BMS from them is 4.5 yrs old now.
The current top contender for cell interconnect is 0.2mm X 30mm nickel, which is a good width to serve as both parallel and series connections in one. I'll likely use wider strip at the connections where the fold will be between the layers of the build (2 to 3 layers, not sure which yet).