Hardware Compression Cell Holders (Published Link on #268)

Simiply put, a good solder joint for a 10 guage wire to a copper strip takes up space. That’s why I’m considering using the braided copper. I do concern about the copper fatigue over time but without further testing, we cant shoot out folding copper strip as a valid series connection.

How did you secure the braid into the module so it would not slip out?

Being hyper critical for funs sake I think braid maybe dangerous with potential to have a broken loose strand shorting

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With sufficient compression it would not budge even when I pull on it really hard. I’m testing how much my 3d printed parts can compress and how much tension it can hold before they crack. As for broken lose strand, I ordered some 4s barley paper rings for the terminals and will probably make covers for between the rings and the holder. Honestly it’s compressed and braided so tight i doubt it would even have the slightest room for the strand to move inside.

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I just use the same compression as given in N.E.S.E modules. I don’t have to worry about that since they are tested well. What I am concerned about is how well the plastic threads will hold over time under force and at elevated temperature. I used ABS, so it should be a bit better.

While I was assembling it, I was kinda annoyed that even with the improvements, I had to be careful about the torque, making sure the threads are not stripped etc. Some surface needed sanding to sit flat. It took me quite some time to assemble 9 modules. I now appreciate how convenient the N.E.S.E modules are, having assembled them both. On top of that, to replace cells, when they get old, I have to go through the whole process again with my modules. Is it worth saving a bit of plastic? I don’t know.

BTW, can’t decide what’s the best way to arrange these modules. Bottom one looks more compact whereas the top one is like @Winfly’s original layout. @uigiroux was wondering about that in the N.E.S.E thread. I’ll be soldering braided copper between the modules.

IMG_20181001_020335

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can’t decide what’s the best way to arrange these modules.

How about like this? You’d flip every other pack so that positive ends are facing each other. Now you could connect the terminals with short wires on the sides.

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stronger = yes probably but need these to be that strong? After all they only need to hold the compression, tbf the weak point on the prints is the layer adhesion (print orientation and optimizations will improve them)

quicker = I don’t think so, the design is not 100% 2.5d so a completly milled version (awith the way cheaper and common portal style mill) would need some work (or be splitted and glued) after it’s milled (cutouts for the busbars/cabels/taps). The preparation for milling and speed isn’t that faster either.

And after all this milling needs way more material and the machines are even less available than printers. Sure milled would work, printing should work also but over all the best solution (with appropriate demand) would be injection molding: simple parts fast to produce, as strong as milled, low amounts of trash and good surface finish and precision

When I say milled I’m talking about getting some long square plastic stock and using a drill stand. You could mark it out and drill pilot holes, then slowly step up the drill size till you have an 18.5mm recess for each battery. Using Forstner bits would give a flat bottom then you just need to cut a slot for the braid to be inserted.

It would take a while but doable.

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Or, you know, just let the terminals come out of the “case” on the opposite side and solder them together directly.

@mishrasubhransu said he’ll be soldering braided copper between the modules. To me this means that the packs should be able to flex which is not accomplished by soldering rigid terminals directly to each other.

Also to get the terminals coming out on the opposite side I imagine he should redesign, reprint and reassemble multiple packs which he said to be pain in the ass.

My original design has terminal opening on both sides. But why do you want both sides to be open? for a series connection you only really need one opening. I closed it to add strength and better isolation between S when putting them side by side.

As for being pain in the ass to assemble. yes if you rely on thread onto the 3d printed holes it will take forever to screw on 8x12S screws without a power tool. I’ve been though that :joy:. to fix that I’m going to make larger hole for screws to push though, shorter screws and longer standoff and make the model the exact height such that when the standoff completely meet both side of the holders. it will be the optimal compression s.t. you don’t have to guess how far to compress it. (RIP sourcing parts from china and it’s taking forever to get here.)

Also i find that with standoff, once you have assembled it once, it’s really easy to unthread and take it off. All you have to do is loosen one end and you can easily rotate the standoff with your thumb. unfortunately that won’t be possible with the longer standoff as mentioned above.

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The reason to have the tabs on both sides should be obvious I thought… With the NESE Modules, I got 6 of the 2s4p modules, but only use one of them as that. I have one 2s4p and five 4p +4p (cut the copper tab in half). Each module holds eight cells, I put four cells one orientation and the other for the opposite, so from one side I can connect the series tabs for 4p, run it up one side starting to the 2s4p module, then end up at the first module for both terminals. Basically this allows you to use half the modules you normally would need to, so it is more convenient IMO.

im sorry you got me very confused. Can you draw it out.

15384031041207550240439069233526 Is this what you mean? correct me if i misunderstood. but still I don’t get why you would need opening on each ends.

I actually have holes on both side. It will be a matter of disassembling them and flipping into the orientation required. Right now they are configured for the axis of the cells to be perpendicular to lenght of the board.

I guess the orientation would depend on how much space you have. If you are using 5P, then no way it’s going to fit in hummies deck when the axis of the cell is parallel to lenght of board.

Yep, I think I am going to do just that. These batteries will go on a shorter deck so if this minimizes the length of battey pack, then sure. I’ll figure it out tonight and even post a pic of it mounted on the deck.

I don’t think I am happy with this. Lots of wasted space. I could definitely reprint and rearrange them to reduce space but I don’t think it is worth it. But I’ll continue to use it until something breaks then shift to N.E.S.E.

@Winfly 's or @Hummie 's design makes perfect sense when decks have cutouts, for flat deck, you need some sort of legs and that reduces space. Might as well go with N.E.S.E, as changing cells is very easy. I am going to stop working on this and wait to see what Winfly or Hummie come up with.

What do you guys think? IMG_20181001_234046(1) IMG_20181001_234039 IMG_20181001_234118 IMG_20181001_231627

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Looks good. What was your final cost? @mishrasubhransu

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I am not selling any, I have all my files shared here. Look in stl folder:

  1. 4P_module_71mm_legs_mirror.stl
  2. 4P_module_71mm_legs.stl
  3. 4P_middle_piece_minimal.stl

If you decide to make this, it’s going to cost you about $10 in 3D printing material and $30 in N.E.S.E tabs for a 10S4P pack.

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That’s what i wanted to know.

Finally have time to put a pack together. Everything fits so we’ll together. Measured 42v end to end. 15384685913845701793853649564292 Yes there are 2 cracked ones. That’s cus those are the thinner old design and I over tightened them.

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