Watts-on's "SpringSlot" 18650 Battery Holder


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Bubba

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May 9, 2018
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image_qarpbi.jpg

image_yspceh.jpg

Great work Watts-ON.

I 3D printed the Elastic_test1 and have some thoughts on improvements

-The slope going up from the bottom of the nubs is causing or leads the elastics to slip upwards and eventually off.
-The nubs are a bit thin on the end and easily broke off when the elastic slipped upwards.
-Could the nub curve be flipped upside down....I mean gradual from the top of the holder instead?

Also, I found that the strength of the holder increased when printed with the positive terminal on the bed so a bit of support is OK.
Looks better printed that way also.

I like the design.
 

watts-on

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May 27, 2017
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Bubba said:
-The slope going up from the bottom of the nubs is causing or leads the elastics to slip upwards and eventually off.
-The nubs are a bit thin on the end and easily broke off when the elastic slipped upwards.
-Could the nub curve be flipped upside down....I mean gradual from the top of the holder instead?

Hmm, I was hoping to get away with it. :(
I can change it to an ideal shape, but it will require supports during printing.

Ive been trying to come up with a solution based on your idea for a latching lever with incorporated cell lifter:

image_bjtuqz.jpg

image_csixav.jpg


image_saqsru.jpg

image_ekndph.jpg


Problems still to solve are:
  • The elastic will collide with the pivot screw unless it can be recessed somehow.
  • The pulling force is reduced due the placement of the nub on the lever, but that is required to allow it to lock in the open position.
  • May be tricky to print without supports.

Just thinking out loud here and inviting any ideas or suggestions...
 

Bubba

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May 9, 2018
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A little support is ok.

You could try and 3D print as 1 piece (that is both pieces already assembled) and use a larger pivot pin.

I like where this is going. Yes this is what I was describing.

I can see now the location of the nubs does have a huge impact, that being said, I liked the through design you had previously on the lever.
 

watts-on

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May 27, 2017
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I've avoided 1-piece printing for moving parts until now. Maybe this is the time to try it. :)

Thinking...
 

Geek

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Aug 15, 2017
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Just a thought... I wonder if you could use a couple of strong neodymium magnets to hold the clamp shut.
 

Bubba

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watts-on said:
I've avoided 1-piece printing for moving parts until now. Maybe this is the time to try it. :)

Thinking...

Send me your design, I can five it a try. Just make sure that the pins extend out past the wall and are large enough.

I also did find a few cloths pins that are a close fit. YA! So the ones I printed before are not going to waste.
Need about 30 of them still so hoping for your next iteration to be a good one.
 

watts-on

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May 27, 2017
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Bubba said:
Send me your design, I can five it a try. Just make sure that the pins extend out past the wall and are large enough.

I also did find a few cloths pins that are a close fit. YA! So the ones I printed before are not going to waste.
Need about 30 of them still so hoping for your next iteration to be a good one.

Sorry, I haven't been around much this week.
The version I showed was never meant to be made, it was just to help me get my head around the mechanics.
I will try to find some time to come up with another version pretty soon.
 

watts-on

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Bubba said:
Send me your design, I can five it a try. Just make sure that the pins extend out past the wall and are large enough.

Ok, Here's what I've come up with:


image_vfpusw.jpg


It prints as a single piece, hopefully with a working pivot. You will need to add supports under the two side nubs, but the rest of the part should print ok without any.
I haven't tried printing it myself, but the .stl file is attached if you want to give it a try.
 

Attachments

  • SpringSlot_Elastic_Latching_Ver1.zip
    61.2 KB · Views: 238

Bubba

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May 9, 2018
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IT WORKS single handed.

To put the cell in and out.
Here is a video of it put together. --> https://drive.google.com/open?id=1AXqBWGhmGZgIGzddfXRThpU3LJQ0txbb

Here are my thoughts:

1. Great work this is what I was looking for.
2. If you move the hole on the lever up a couple of mm you might get better contact at the center of the cell.
3. I find the lever doesn't go down into the tiny groves for the prongs on the lever. You could move the base mounting hole at the negative terminal and make the lifter all the way across. That being the part of the lever that rests under the cell would be thicker.
4. I found the walls to be stronger on this iteration than the previous ones. i.e. above the posts for the rubber bands and the lever itself.
5. The little overhang on the lever (where the elastic goes through) broke off on first use since it's a bit weak there. But isn't necessary. See the pics.

image_aykxss.jpg

image_medkfq.jpg
 

Lucan

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Jan 30, 2019
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Why do you need the nubs? You could simply loop the elastic around the cell holder, and under the screw on the far side. Yes you'd loose some force since it won't be doubled up, but how much force do you really need?
 

Bubba

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May 9, 2018
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301
Lucan said:
Why do you need the nubs? You could simply loop the elastic around the cell holder, and under the screw on the far side. Yes you'd loose some force since it won't be doubled up, but how much force do you really need?

I you anchored the bands to the screw that secures the holder you will end up with the elastics pulling the lever to the open position.
The nubs provide for a proper angle resulting in the lever being pulled towards the cell rather than away from.

If the elastics were in front of the pivot point this might work, but I think then they would also be in the way.

The elastic was doubled over because I used a large elastic instead of a small one.
 

watts-on

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May 27, 2017
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brettwatty said:
...Nice work mate. Your 3D printing / CAD skill are next level mate :)
Thanks mate. I'm strictly amateur, but having fun with it. :D

Bubba said:
IT WORKS single handed.

Great news! thanks for reporting back. :)

Bubba said:
2. If you move the hole on the lever up a couple of mm you might get better contact at the center of the cell.
Not sure I follow?

Bubba said:
3. I find the lever doesn't go down into the tiny groves for the prongs on the lever. You could move the base mounting hole at the negative terminal and make the lifter all the way across. That being the part of the lever that rests under the cell would be thicker.
Hmm, I left the hole in that location because it makes it compatible with the commercial single slot cell holder's mounting holes. I could sure add more clearance for the prongs though..

Bubba said:
4. I found the walls to be stronger on this iteration than the previous ones. i.e. above the posts for the rubber bands and the lever itself.
I thickened the walls of the lever since it now has to support the force of the pivot, but I don't think I altered the walls of the main body.

Bubba said:
5. The little overhang on the lever (where the elastic goes through) broke off on first use since it's a bit weak there. But isn't necessary. See the pics.
I've beefed it up a bit now.

Lucan said:
Why do you need the nubs? You could simply loop the elastic around the cell holder, and under the screw on the far side. Yes you'd loose some force since it won't be doubled up, but how much force do you really need?

I was thinking exactly the same thing, so I came up with another version:


image_cbigwp.jpg


The nubs on the end ensure the elastic is held low down to ensure they pull form the correct angle.
You can wrap the elastic right round the whole thing, or hook the ends onto the positive terminal screw ( may be worth putting some heat-shrink on the thread if using that method so the threads don't damage the elastic).
Still needs to be printed with some supports though.

.stl file attached..
 

Attachments

  • SpringSlot_Elastic_Latching_Ver2.zip
    62.1 KB · Views: 289

watts-on

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Following a request from another user, I have created a quad version of the SpringSlot, that will fit the footprint (apart from the levers) of the commercially available quad (4-gang) type, like this:




image_cpiomr.jpg




The levers are slightly narrower than the single slot ones so are incompable.
I haven't 3D printed this myself to check the dimensions / fit, so please report back any problems.




image_nvutym.jpg




.slt files attached.
 

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  • Sprint_Slot_Quad_Ver1.zip
    4.1 MB · Views: 297

watts-on

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Following a further request, I have now created another variant specifically for @brettwatty 's 4 channel cell tester.


image_hhcnml.jpg


This has holes for the new location for the temperature sensors.
The files also include a combined insulator and spacer. This not only ensures the springs are insulated from the board, but also provides clearance of up to 1.5mm to allow for the leads of component fitted on the reverse side.


image_xyoypu.jpg


I dont have one of the 4 channel boards, so am not able the test it for fit, so please report back any issues and I will update it.

STL files attached:
 

Attachments

  • STL_SpringSlot_ASCD_Nano_x4.zip
    164.8 KB · Views: 101

ForumSn0w

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Jun 24, 2021
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I know this is an old thread, but is there any chance someone could post a version of the Spring Slot that will take 26650 cells? I have a bunch of new K2 Energy LiFeP04 in 26650 that I need to go through and would really like to put this awesome design to work. I don't own a 3D printer and have no experience with CAD tools or else I would have tried making them myself. Just going to order them from JLCPCB if I can get some .STL made.
 

ForumSn0w

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I will try to find some time over the next few days to create a 26650 version.
Awesome, I really appreciate your time you and others have put into this system. It really is a cool way to hold cells while charging. I even tried editing a couple of the previous STL files on Tinker cad, but it just wasn't coming out right. I was halfway afraid of spending the money on having them printed just to come out wrong as well.
 

watts-on

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May 27, 2017
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...is there any chance someone could post a version of the Spring Slot that will take 26650 cells?

Hey @ForumSn0w, Attached is the 26650 version.

I don't have access to any 26650's myself, but, have assumed they are the same length as 18650, but 26mm in diameter?
I've printed one out to check dimension and I think it is ok, but I would caution you about ordering too many on your first order as I kinda design stuff with tolerances for consumer grade printers. Professional printing may yield slightly different results.

Here's a pic of the one I printed, with an 18650 fitted for scale:

Spring26650b.JPG


STL Files attached:
 

Attachments

  • SpringSlot_26650_V1.zip
    807.1 KB · Views: 4
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